e-Tax Electronic Filing — Automated Input to NTA Tax Return Preparation Corner using Claude in Chrome

This guide provides step-by-step instructions for using Claude in Chrome to automate input into the NTA Tax Return Preparation Corner for filing final tax returns, including blue returns, income tax, and consumption tax.

Prerequisites

Completion of income tax calculation using the
```
/income-tax
```
skill
Completion of financial statements (P/L, B/S) using the
```
/settlement
```
skill
Completion of consumption tax calculation using the
```
/consumption-tax
```
skill (if applicable)
```
shinkoku.config.yaml
```
is properly configured
One of the browser automation tools is available (see "Browser Automation Method Selection" below)

Browser Automation Method Selection

There are three methods for inputting data into the Tax Return Preparation Corner:

Method A: Claude in Chrome (Recommended)

Item	Details
Supported Environments	Native Chrome on Windows / macOS
Prerequisites	Claude in Chrome extension installed
Advantages	No OS detection issues, no additional configuration required

Method B: Antigravity Browser Sub-Agent

Item	Details
Supported Environments	Windows / macOS / Linux (Antigravity IDE)
Prerequisites	Antigravity IDE installed with `browser_subagent` tool available
Advantages	Uses native Chrome, no OS spoofing required, works on Linux

Method C: Playwright CLI (Fallback)

Item	Details
Supported Environments	WSL / Linux, or environments where Claude in Chrome/Antigravity are unavailable
Prerequisites	`@playwright/cli` + Playwright CLI skill + `etax-stealth.js` (OS spoofing script)
Restrictions	Headed mode required (physical operation needed for QR code authentication)

Decision Logic

1. Is Claude in Chrome tool (browser_navigate, etc.) available?
   → Yes: Use Method A
   → No: Proceed to next

2. Is Antigravity's browser_subagent tool available?
   → Yes: Use Method B
   → No: Proceed to next

3. Is `playwright-cli` command available via Bash tool?
   → Yes: Use Method C (launch in headed mode)
   → No: Display error

   Error Message:
   "Claude in Chrome, Antigravity Browser Sub-Agent, or Playwright CLI is required for input to the Tax Return Preparation Corner. Refer to the 'Browser Automation' section in README.md for setup instructions."

Operation Method for Method B

Antigravity's

browser_subagent

operates with high-level task descriptions. Describe each step's input operation in natural language and delegate to

browser_subagent

Examples:

"Open https://www.keisan.nta.go.jp/kyoutu/ky/sm/top_web#bsctrl"
"Click the 'Yes' radio button for 'Do you have a My Number Card?'"
"Enter '1' into the input field with name='sonekiKeisansyoFromMonth'"

Note: Antigravity uses native Chrome, so OS spoofing with
etax-stealth.js
is not required.

Session Start Procedure for Method C

Steps to open browser with Playwright CLI:

Set environment variable:

PLAYWRIGHT_MCP_INIT_SCRIPT=skills/e-tax/scripts/etax-stealth.js

Launch browser:

playwright-cli -s=etax open <url> --headed --browser=chrome

Execute subsequent commands with
```
-s=etax
```
session specification

Load Configuration (Execute First)

Load
```
shinkoku.config.yaml
```
using the Read tool
If the file does not exist, guide the user to execute the
```
/setup
```
skill and exit
Understand configuration values:
- Taxpayer profile (name, address, My Number, etc.)
- Business information (trade name, industry type, etc.)
- Filing method (e-Tax/mail/counter)

Load Progress Information

Load
```
.shinkoku/progress/progress-summary.md
```
using the Read tool (if it exists)
Load the following handover documents using the Read tool (if they exist):
- ```
.shinkoku/progress/06-settlement.md
```
  — Settlement results (P/L/B/S data)
- ```
.shinkoku/progress/07-income-tax.md
```
  — Income tax calculation results
- ```
.shinkoku/progress/08-consumption-tax.md
```
  — Consumption tax calculation results
- ```
.shinkoku/progress/02-assess.md
```
  — Taxability determination results
Check
```
status
```
in
```
.shinkoku/progress/10-etax.md
```
:
- If
```
status: interrupted
```
  → Follow resumption procedure in "Interruption/Resumption Protocol" below
- If
```
status: completed
```
  → Notify user that filing is complete and confirm intention to re-execute
If calculation results do not exist yet, guide user to execute
```
/income-tax
```
and
```
/settlement
```
first

Interruption/Resumption Protocol

Rules common to all steps. If the user requests interruption (e.g., "I want to stop", "That's it for today", "I'll continue later"), follow these steps:

Interruption Procedure

Confirm input contents of current step — Check for unsaved input
Guide to download .data file — Display the following using AskUserQuestion:

We recommend saving the input data from the preparation corner as a .data file.
Click the "Temporarily save input data" button at the top of the screen (or the "Save input data up to this point" link at the bottom of the page)
and download the file.

Please select "Downloaded" once the download is complete.

Options: "Downloaded" / "Skip (do not save)"
If "Skip" is selected, warn the user that they may have to start over from the beginning next time

Record progress file — Output to
```
.shinkoku/progress/10-etax.md
```
in the following format using the Write tool:

---
step: 10
skill: e-tax
status: interrupted
last_completed_step: "{Last completed step number (e.g., 3)}"
last_url: "{Browser URL at time of interruption}"
data_file_saved: {true/false}
interrupted_at: "{Current date YYYY-MM-DD}"
fiscal_year: {tax_year}
---

# e-Tax Electronic Filing (Interrupted)

## Status at Interruption

- Last completed step: Step {N}
- URL at interruption: {URL}
- .data file saved: {Yes/No}

## How to Resume Next Time

1. Re-execute the `/e-tax` skill
2. If you have a .data file, resume from "Create using saved data"
3. If you don't have a .data file, start over from step 0

Notify user of completion of interruption — Guide user on how to resume next time and exit

Resumption Procedure

status: interrupted

is detected in

.shinkoku/progress/10-etax.md

Read interruption information (
```
last_completed_step
```
,
```
data_file_saved
```
)
Display the following using AskUserQuestion:

Your previous e-Tax input was interrupted at step {N}.

Please select how to resume.

Options:
- "Resume from .data file" (display only if
```
data_file_saved: true
```
  )
- "Start over from the beginning"
- "Discard interruption record and exit"

If resuming from .data file:
- Access the top page of the Tax Return Preparation Corner
- Select "Create using saved data" → "Resume creation"
- Guide user to upload the .data file
- After loading is complete, resume from the step following
```
last_completed_step
```
If starting over from the beginning:
- Start normally from step 0

Step 0: Verify Required Data

Verify that all data required for input to the Tax Return Preparation Corner is available.

Verification Items

[1] Tax amount calculated
    - .shinkoku/progress/07-income-tax.md exists and has status: completed

[2] Profile complete
    - Is name (last/first) registered?
    - Is address registered?
    - Is competent tax office name registered?

[3] Financial statement data
    - P/L/B/S calculation results are available

[4] Consumption tax (if applicable)
    - .shinkoku/progress/08-consumption-tax.md exists and has status: completed

[5] Sanity check
    - Execute `tax_calc.py sanity-check`
    - If error > 0: Abort input and prompt correction using `/income-tax` skill
    - If warning > 0: Confirm with user before proceeding

Overall Screen Transition Flow

┌─────────────────────────────────────────────────────┐
│ CC-AA-010 Select submission method to tax office     │
│   My Number Card: Yes → Smartphone: Yes              │
│   → "Use smartphone"                                 │
└──────────────┬──────────────────────────────────────┘
               ▼
┌─────────────────────────────────────────────────────┐
│ CC-AE-090 Select return form to create               │
│   Select "Financial Statement/Income Statement (+ Income Tax)" │
│   → doSubmitCMW0900(2,'25')                          │
│                                                         │
│   *For consumption tax only, create separately:       │
│   → doSubmitCMW0900(3,'25')                          │
└──────────────┬──────────────────────────────────────┘
               ▼
┌─────────────────────────────────────────────────────┐
│ CC-AE-600 Select My Number Portal linkage            │
│   → "Do not use My Number Portal linkage"            │
└──────────────┬──────────────────────────────────────┘
               ▼
┌─────────────────────────────────────────────────────┐
│ CC-AA-024 Confirmation before e-Tax filing            │
│   → "Agree to terms of use and proceed"              │
└──────────────┬──────────────────────────────────────┘
               ▼
┌─────────────────────────────────────────────────────┐
│ CC-AA-440 QR code authentication                     │
│   ★ User physical authentication required            │
│   Read QR code with smartphone                       │
│   → Automatic transition after My Number Card authentication │
└──────────────┬──────────────────────────────────────┘
               ▼
       ┌───────┴───────┐
       ▼               ▼
  Financial Statement Corner  Income Tax Corner
  (With business income)      (Salary only, etc.)

Financial Statement Corner Flow

/kessan/ac/r7/top → ac0300 (Type selection) → aa0200 (P/L input)
  → aa0100 (Blue return special deduction) → preAoiroCalc (B/S input)
  → aa0700 (Income confirmation) → ac0500 (Address and name) → Print/Save
  → Transition to Income Tax Corner

Income Tax Corner Flow

SS-AA-010a (Income selection) → SS-AA-050 (Income input hub)
  → SS-CA-010 (Salary input) / SS-CB-xxx (Business income) / Miscellaneous income
  → SS-AA-070a (Deductions 1/2) → SS-AA-080 (Deductions 2/2)
  → SS-AA-090 (Calculation result confirmation)
  → SS-AC-010a (Payment method) → SS-AC-020a (Resident tax, etc.)
  → SS-AC-030 (Basic information) → SS-AC-040 (My Number)
  → Step 5.5 (Decision gate) → Step 6 (Digital signature and transmission protocol)

Consumption Tax Corner Flow (After Income Tax Completion)

Income tax completion → "Create consumption tax return here"

20% Special Provision:
  ac0100 (Condition determination) → ac0250 (Income category selection) → Sales input hub → Sales input detail
  → Sales input hub → Interim payment → ac0300 (Calculation result) → Tax payment location, etc.
  → Step 6.5 (Digital signature and transmission protocol)

Simplified Taxation:
  ac0100 (Condition determination) → ac0250 (Income category/business category selection) → Sales input hub → Sales input detail
  → Sales input hub → ak2140 (Input tax credit method selection)* → Interim payment → ac0300 (Calculation result)
  → Tax payment location, etc. → Step 6.5 (Digital signature and transmission protocol)
  *Only if operating two or more types of businesses

Standard Taxation:
  ac0100 (Condition determination) → ac0250 (Income category selection) → Sales/purchase input hub → Sales input detail
  → ai3610 (Settlement amount table)* → Sales/purchase input hub → Interim payment → ac0300 (Calculation result)
  → Tax payment location, etc. → Step 6.5 (Digital signature and transmission protocol)
  *Only if cumulative calculation is selected

Step 1: Access Tax Return Preparation Corner

Start URL

https://www.keisan.nta.go.jp/kyoutu/ky/sm/top_web#bsctrl

CC-AA-010: Select Submission Method to Tax Office

Screen number: CC-AA-010

"Do you have a My Number Card?" → Click "Yes" radio button
"Do you have a smartphone or IC card reader/writer compatible with My Number Card reading?" → Click "Yes"

Click "Use smartphone"

JS:

doSubmitCSW0100('1','3','/ky/sm/csw0100_myno_qr')

CC-AE-090: Select Return Form to Create

Screen number: CC-AE-090

Options (FY2025):

Income Tax →
```
doSubmitCMW0900(1,'25')
```
Financial Statement/Income Statement (+ Income Tax) →
```
doSubmitCMW0900(2,'25')
```
← If you have business income
Consumption Tax →
```
doSubmitCMW0900(3,'25')
```
Gift Tax →
```
doSubmitCMW0900(4,'25')
```

Judgment Criteria:

With business income → "Financial Statement/Income Statement (+ Income Tax)"
Without business income (salary only, etc.) → "Income Tax"
Consumption tax is created separately after income tax completion

CC-AE-600: Select My Number Portal Linkage

→ Click "Do not use My Number Portal linkage"

CC-AA-024: Confirmation Before e-Tax Filing

→ Click "Agree to terms of use and proceed"

Note: Environment check
termnalInfomationCheckOS_myNumberLinkage()
is executed. No issues with Chrome/Edge on Windows/macOS.

CC-AA-440: QR Code Authentication

★ Wait for user operation — Pause browser operation

The agent must not operate the browser on this screen. Pause using AskUserQuestion tool and do not proceed to next step until user reports authentication completion.

Display the following using AskUserQuestion:

QR code authentication screen is displayed.
Read the QR code with your smartphone's My Number Portal app
and authenticate with your My Number Card.

Please select "Authentication completed" once authentication is done.

Options: "Authentication completed" / "QR code is not displayed"
If "QR code is not displayed" is selected, refer to ⚠️ Notes for Playwright CLI use below for troubleshooting
Do not perform any browser operations or screen transitions until user selects "Authentication completed"

After authentication is completed, automatically transition to next screen.

⚠️ Notes for Playwright CLI use: Server bake function patches are automatically applied by specifying

etax-stealth.js

in the

PLAYWRIGHT_MCP_INIT_SCRIPT

environment variable, but if QR code is not displayed, check the return value of

getClientOS()

in the console. If it is not

'Windows'

, execute the following manually:

javascript

window.getClientOS = function() { return 'Windows'; };
displayQrcode();

Step 2: Input Blue Return Financial Statement (If you have business income)

⚠️ Native dialog warning: If screen does not transition after clicking "Next", a native dialog (alert/confirm) may be displayed. Refer to "Detection and Handling of Native Dialogs" in Technical Insights.

/kessan/ac/pre/ac0300: Select Financial Statement Type

Radio buttons:

Blue Return Financial Statement ← For blue return filers
Income Statement (For white return filers)
Blue Return Financial Statement (For cash basis)

/kessan/ac/aa0200: Input Profit and Loss Statement (P/L)

URL:

https://www.keisan.nta.go.jp/kessan/ac/aa0200#bsctrl

Period Input

Field	name	Default
Start month	`sonekiKeisansyoFromMonth`	1
Start day	`sonekiKeisansyoFromDay`	1
End month	`sonekiKeisansyoToMonth`	12
End day	`sonekiKeisansyoToDay`	31

Sales (Revenue) Amount

Click "Input" button → Transition to

/kessan/ac/aa0201

monthly sales/purchase input subpage.

Fields for aa0201:

```
uriageKingaku1
```
~
```
uriageKingaku12
```
: Monthly sales
```
siireKingaku1
```
~
```
siireKingaku12
```
: Monthly purchases
```
kajisyohi
```
: Household expenses, etc.
```
zatusyunyu
```
: Miscellaneous income

Totals:

uriageKingakuGokei

siireKingakuGokei

Expenses (Rows 8~31)


sozeiKoka
nidukuriUntin
suidoKonetuhi
ryohiKotuhi
tusinhi
kokokuSendenhi
settaiKosaihi
songaiHokenryo
syuzenhi
syomohinhi
/kessan/ac/init/aa0203
fukuriKoseihi
/kessan/ac/aa0205
gaichukotin
/kessan/ac/aa0206
/kessan/ac/aa0207
kasidaorekin
keihiNiniKamoku1
keihiNiniKamoku2
keihiNiniKamoku3
zappi

Row	Item	name (direct input)	Notes
8	Taxes and public dues	`sozeiKoka`
9	Packing and transportation expenses	`nidukuriUntin`
10	Water, light, and heat expenses	`suidoKonetuhi`
11	Travel and transportation expenses	`ryohiKotuhi`
12	Communication expenses	`tusinhi`
13	Advertising and promotion expenses	`kokokuSendenhi`
14	Entertainment expenses	`settaiKosaihi`
15	Property insurance premiums	`songaiHokenryo`
16	Repair expenses	`syuzenhi`
17	Supplies expenses	`syomohinhi`
18	Depreciation expenses	—	"Input" → `/kessan/ac/init/aa0203`
19	Welfare expenses	`fukuriKoseihi`
20	Salaries and wages	—	"Input" → `/kessan/ac/aa0205`
21	Outsourcing expenses	`gaichukotin`
22	Interest and discount fees	—	"Input" → `/kessan/ac/aa0206`
23	Rent expenses	—	"Input" → `/kessan/ac/aa0207`
24	Bad debt expenses	`kasidaorekin`
25	Fees for tax accountants, etc.	`keihiNiniKingaku1`	Item name: `keihiNiniKamoku1`
26	Earthquake-related expenses	`keihiNiniKingaku2`	Item name: `keihiNiniKamoku2`
27-30	Optional items	`keihiNiniKingaku3` ~ `6`	Item names: `keihiNiniKamoku3` ~ `6`
31	Miscellaneous expenses	`zappi`

Aggregation hidden fields:

keihiSannyugakuGokei

kyuryoTinginTotalGokei

risiWaribikiryoGokei

tidaiYatinGokei

Carryback amounts, etc.

kurimodosiNiniKamoku1

kurimodosiNiniKingaku1

kurimodosiNiniKamoku2

kurimodosiNiniKingaku2

Dedicated employee salaries

```
senjusyaKyuyoTotalGokei
```
(hidden, separate screen via "Input" button)
```
kasidaoreKuriireGokei
```
(hidden)

Calculation Results (Automatic)

```
disp_aoiroKojomaeSyotokuKingaku
```
= Sales - Cost of goods sold - Expenses + Carryback amounts - Dedicated employee salaries, etc.

/kessan/ac/submit/aa0100: Blue Return Special Deduction

Select deduction amount in Q&A format:

Option	value	Condition
¥100,000	2
¥550,000	3
¥650,000	1	e-Tax filing is required. Error KS-E10089 for paper filing

Field:

aoiroTokubetuKojoSentakugaku

If selecting ¥650,000, electronic book storage or e-Tax filing is required.

⚠️ Native dialog warning: If you select ¥650,000 and proceed, a native dialog with error KS-E10089 (e-Tax filing required) will be displayed for paper filing. If screen does not transition, confirm with user whether dialog is displayed.

Input Balance Sheet (B/S)

URL:

/kessan/ac/preAoiroCalc

Assets Section

Array format:

sisannobuTaisyohyoDetailDataList[N].kisyuKingaku

.kimatuKingaku

index	Account Item
0	Cash
1	Current deposits
2	Time deposits
3	Other deposits
4	Notes receivable
5	Accounts receivable
6	Securities
7	Inventory assets
8	Prepaid expenses
9	Loans receivable
10	Buildings
11	Building附属设备
12	Machinery and equipment
13	Vehicles and transportation equipment
14	Tools, fixtures, and supplies
15	Land
16-23	Optional items

Liabilities and Equity Section

Array format:

fusainobuTaisyohyoDetailDataList[N].kisyuKingaku

.kimatuKingaku

index	Account Item
0	Notes payable
1	Accounts payable
2	Loans payable
3	Accrued expenses
4	Unearned revenue
5	Deposits received
6	Allowance for bad debts
7-15	Optional items
16	Capital contributions
17	Owner's drawings
18	Owner's capital
19	Income before blue return special deduction (automatic from P/L)

Important: Total assets at end of period must equal total liabilities at end of period (KS-E40003)

⚠️ Native dialog warning: If you click "Next" after B/S input and total assets do not equal total liabilities, a native dialog with error KS-E40003 will be displayed. If screen does not transition, confirm with user whether dialog is displayed.

/kessan/ac/ac0500: Input Address, Name, etc.

Field	name
Postal code	`jitakuZip`
Prefecture	`jitakuPrefectureId`
Municipality and below	`jitakuAddress`
Business office address (if applicable)	`jimusyoAddress`
Tax office to submit to	`zeimusyoName`
Name in kanji (last)	`nameKanjiSei`
Name in kanji (first)	`nameKanjiMei`
Industry name	`gyosyuName`
Trade name	`yago`
Submission date	`teisyutuYear` / `teisyutuMonth` / `teisyutuDay`

Financial Statement Completion → Transition to Income Tax Corner

Click the "Create income tax return here" button on the print/data save screen (

/kessan/ac/submit/ac0600

) to transition to the income tax corner (address and name are carried over).

⚠️ Native dialog warning: When clicking this button, a native dialog with warning KS-W10035 (Have you confirmed printing?) may be displayed. If screen does not transition, confirm with user whether dialog is displayed and guide them to click "OK".

Step 3: Input Income Tax Return

⚠️ Native dialog warning: If screen does not transition after clicking "Next", a native dialog (alert/confirm) may be displayed. Refer to "Detection and Handling of Native Dialogs" in Technical Insights.

SS-AA-010a: Select Income to Declare, etc.

URL:

https://www.keisan.nta.go.jp/r7/syotoku/taM010a40_doInitialDisplay#bbctrl

Date of Birth

Field	name
Year	`inOutDto.shnkkBirthymdYy`
Month	`inOutDto.shnkkBirthymdMm`
Day	`inOutDto.shnkkBirthymdDd`

Income Type Selection (Checkboxes)

Income	name	Typical Selection
Salary	`inOutDto.kyuy`	Company employee: checked
Business (sales, etc.)	`inOutDto.jgyoEgyoTo`	Sole proprietor: checked
Business (agriculture)	`inOutDto.jgyoNogyo`
Real estate	`inOutDto.fdosn`
Miscellaneous (fees, etc.)	`inOutDto.ztsGyomSnt`	Cryptocurrency, etc.: checked
Public pensions, etc.	`inOutDto.kotkNnknKgyoNnknEtc`
Retirement allowance	`inOutDto.tasyku`
Stocks, etc.	`inOutDto.hatoKbshkJyotRsh`
Futures transactions	`inOutDto.skmnTrhk`
Temporary	`inOutDto.ichj`

Typical Patterns for shinkoku:

Company employee + side business (business income):
```
kyuy
```
+
```
jgyoEgyoTo
```
+
```
ztsGyomSnt
```
(if cryptocurrency)
Salary income only:
```
kyuy
```

SS-AA-050: Income/Income Input Hub

Input links are displayed for each selected income type. Click each link to transition to individual input screens.

SS-CA-010: Input Withholding Tax Statement for Salary Income

URL:

https://www.keisan.nta.go.jp/r7/syotoku/taS510a10_doAdd_nncyzm#bbctrl

Main Input Fields

Label	name	Notes
A: Payment amount	`inOutDto.shhraKngk`	Required
D: Withholding tax amount	`inOutDto.gnsnTyosyuZegk`
Amount of social insurance premiums, etc.	`inOutDto.sykaHknryoToKngk`
G: Payer's address	`inOutDto.shhrasyJysyKysyOrSyzach`	Within 28 characters
H: Payer's name or trade name	`inOutDto.shhrasyNameOrMesyo`	Within 28 characters

Conditional Fields (Displayed when "Yes" is selected via radio button)

Label	name	Display Condition
Life insurance premium deduction amount	`inOutDto.semeHknryoKojygk`	`semeHknryoKojygkKsaUm=1`
New life insurance premium amount	`inOutDto.shnSemeHknryoKngk`	Above is yes
Old life insurance premium amount	`inOutDto.kyuSemeHknryoKngk`	Above is yes
Long-term care insurance premium amount	`inOutDto.kagIryoHknryoKngk`	Above is yes
New individual pension insurance premium amount	`inOutDto.shnKjnNnknHknryoKngk`	Above is yes
Old individual pension insurance premium amount	`inOutDto.kyuKjnNnknHknryoKngk`	Above is yes
Earthquake insurance premium deduction amount	`inOutDto.jshnHknryoKojygk`	`jshnHknryoKojygkKsaUm=1`
Special deduction for housing loans, etc.	`inOutDto.jyutkKrirknToTkbtsKojyGk`	`jyutkKrirknToTkbtsKojyGkKsaUm=1`

Radio Buttons (Selection of presence/absence of description)

Field	name	Value
Description of spouse eligible for deduction	`inOutDto.kojyTashoHagsyKsaUm`	1(Yes)/2(No)
Description of dependents eligible for deduction	`inOutDto.kojyTashoFyoShnzkKsaUm`	1(Yes)/2(No)
Description of life insurance premium deduction amount	`inOutDto.semeHknryoKojygkKsaUm`	1(Yes)/2(No)
Description of earthquake insurance premium deduction amount	`inOutDto.jshnHknryoKojygkKsaUm`	1(Yes)/2(No)
Description of special deduction for housing loans, etc.	`inOutDto.jyutkKrirknToTkbtsKojyGkKsaUm`	1(Yes)/0(No)

SS-AA-070a: Input Deductions (1/2) — Expense-based Deductions

Hub screen with input links. Click each deduction to transition to individual input screens.

Supported deductions:

Social insurance premium deduction (displayed as "Input done" if already input via withholding tax statement)
Small business mutual aid premium deduction (iDeCo, etc.)
Life insurance premium deduction
Earthquake insurance premium deduction
Casualty loss deduction / Disaster relief
Medical expense deduction
Donation deduction (including hometown tax payment — one-stop special case also needs input)

SS-AA-080: Input Deductions (2/2) — Personal Deductions, Housing Deductions, etc.

Supported deductions:

Spouse (special) deduction
Dependent deduction / Special deduction for specified relatives
Widow/single parent deduction
Working student deduction
Disability deduction
Basic deduction (automatic calculation display)
Special deduction for housing loans, etc.
Special deduction for seismic retrofitting of housing, etc.
Estimated tax payment amount
Carryforward loss amount

SS-AA-090: Confirm Calculation Results

Screen to confirm income tax amount calculated from input contents.

Display items:

Income amount/income amount (by income type)
Total income deductions
Taxable income amount (rounded down to nearest ¥1,000)
Tax amount on above (using tax table)
Net income tax amount
Special reconstruction income tax amount (2.1% of base income tax amount)
Amount of income tax and special reconstruction income tax
Withholding tax amount
Declared tax payment amount (rounded down to nearest ¥100) / Tax refund amount

Compare with shinkoku calculation results here (refer to "Step 5: Confirm Declaration Contents" below).

Each section has a "Correct" button to return to previous screen.

SS-AC-010a: Input Payment Method, etc.

Displayed if payment amount is incurred. If refund is due, refund account input screen (SS-AB-010a) is displayed.

Field	type	name	Notes
Apply for tax deferment	checkbox	—	Note that interest tax will be charged
Payment method	select	`inOutDto.nofHoho`	Required

Payment method options:

value	Method
1	Transfer tax payment (available for timely declarations)
2	Electronic tax payment (direct payment/internet banking)
3	Credit card payment
5	Convenience store payment
6	Over-the-counter payment at financial institutions, etc.

If refund is due, input refund account information:

Financial institution name, branch name, account number, account holder name

SS-AC-020a: Assets and Liabilities, Resident Tax, etc.

Settings related to resident tax (special collection from salary or self-payment, etc.).

SS-AC-030: Input Basic Information

Label	name	Notes
Name in katakana (last)	`inOutDto.nameKnSe`	Within 11 characters
Name in katakana (first)	`inOutDto.nameKnMe`
Name in kanji (last)	`inOutDto.nameKnjSe`	Within 10 characters
Name in kanji (first)	`inOutDto.nameKnjMe`
Phone number type	`inOutDto.rnrkSkKbn`	Home/work/mobile
Phone number (area code)	`inOutDto.shgaKykbn`
Phone number (local number)	`inOutDto.shnaKykbn`
Phone number (line number)	`inOutDto.knyusyBngo`
Tax payment location category	`inOutDto.nozeCh`	1=Residence, 2=Business office, etc.
Postal code	`inOutDto.yubnBngoGnzaAddress`	7 digits
Prefecture	`inOutDto.tdofknGnzaAddress`	select
Municipality	`inOutDto.shkcyosnGnzaAddress`	select linked to prefecture
Chome, block, etc.	`inOutDto.cyomBnchToGnzaAddress`	Within 28 characters
Building name	`inOutDto.ttmnMeGoshtsGnzaAddress`	Within 28 characters
Tax office to submit to (prefecture)	`inOutDto.tesytSkZemsyTdofkn`	select
Tax office to submit to	`inOutDto.tesytSkZemsyZemsy`	select linked to prefecture
Occupation	`inOutDto.job`	Within 11 characters
Trade name/pen name	`inOutDto.ygoGgo`	Within 30 characters
Head of household's name	`inOutDto.stanshNameKnj`
Relationship	`inOutDto.stanshKrTsdkgr`	select
Submission date	`inOutDto.tesytYmdYy` / `Mm` / `Dd`

SS-AC-040: Input My Number

Screen to input My Number (12 digits). Verification via check digit algorithm is performed.

Step 4: Input Consumption Tax Return (If applicable)

⚠️ Native dialog warning: If screen does not transition after clicking "Next", a native dialog (alert/confirm) may be displayed. Refer to "Detection and Handling of Native Dialogs" in Technical Insights.

After completing income tax return, transition to consumption tax corner by selecting "Create other return forms" →

doSubmitCSW0900(3,'25')

ac0100: Condition Determination, etc.

URL:

https://www.keisan.nta.go.jp/syouhi/ac0100/submit.htmj#bsctrl

Field	name	Notes
Taxable sales for base period	`kijunKazeiUriage`	FY2023
Invoice-issuing business operator	`invoice`	true/false
Select simplified taxation system	`kani`	true/false
Accounting method	`zeikomi`	Tax-included/tax-excluded

Additional display if invoice=yes

Field	name	Notes
New taxable business operator?	`newKazeiJigyosya`	true/false
Apply 20% special provision?	`niwariTokurei`	true/false

Additional display for standard taxation

Field	name	Notes
Input tax credit calculation method	`siireKeisanHouhou`	warimodosi/tumiage

Display logic for condition determination screen (branch by base period)

Displayed options change depending on

kijunKazeiUriage

(taxable sales for base period):

Condition	New taxable business operator?	20% special provision?	Simplified taxation?
Base period=0, invoice=yes	Display	Display	Not displayed
Base period=3,000,000, invoice=yes	Display	Display	Display
Base period=60,000,000, invoice=yes	Not displayed	Not displayed	Display

Standard taxation only: Button for "Those who select cumulative calculation as tax amount calculation method" (within collapsible section)

Branch Logic

Condition	Transition route
Invoice=yes & 20% special provision=yes	20% Special Provision
Simplified taxation=yes	Simplified Taxation
Other than above	Standard Taxation

ac0250: Select Income Category

URL:

https://www.keisan.nta.go.jp/syouhi/ac0250/submit.htmj#bsctrl

Select all applicable income categories. Taxation method (standard/simplified) and accounting method (tax-included/tax-excluded) are displayed in the header.

Label	name	Notes
Business income (sales, etc.)	`jigyoSyotokuEigyo`	Main target
Business income (agriculture)	`jigyoSyotokuNogyo`
Real estate income	`fudosanSyotoku`
Miscellaneous income (royalties, etc.)	`zatuSyotoku`
Capital gains from business fixed assets, etc.	`jotoSyotoku`	Displayed only for standard taxation

Simplified taxation only: Select business category

For simplified taxation, there are sub-selections for business category (Type 1~6) for each income category:

Field	name	Notes
Business category (Type 1)	`jigyoSyotokuEigyoJigyoKubun1`	Wholesale business
Business category (Type 2)	`jigyoSyotokuEigyoJigyoKubun2`	Retail business
Business category (Type 3)	`jigyoSyotokuEigyoJigyoKubun3`	Manufacturing, etc.
Business category (Type 4)	`jigyoSyotokuEigyoJigyoKubun4`	Other
Business category (Type 5)	`jigyoSyotokuEigyoJigyoKubun5`	Service business, etc.
Business category (Type 6)	`jigyoSyotokuEigyoJigyoKubun6`	Real estate business

Standard taxation only: Business fixed assets, etc.

Field	name	Notes
Purchases of business fixed assets, etc.	`gyomuyosisanKonyu`	checkbox

Sales Input (Common Form for All Routes)

URL patterns:

20% Special Provision:
```
/syouhi/at3600/inputEigyo.htmj
```
Simplified Taxation:
```
/syouhi/ak3600/inputEigyo.htmj
```
Standard Taxation:
```
/syouhi/ai3600/inputEigyo.htmj
```

Field	name	Notes
Sales (revenue) amount	`uriageWari`	Required. Total tax-included amount
Tax-exempt sales	`menzeiUriageWari`
Non-taxable sales	`hikazeiUriageWari`
Exempt transactions	`jigyoFukazeiUriageWari`
Reduced tax rate (6.24%) applicable amount	`kazeiUriage624PercentWari`
Consideration for returns, etc. (reduced)	`uriageTaikaKeigen.uriageTaika624Percent`
Consideration for returns, etc. (standard)	`uriageTaikaKeigen.uriageTaika78Percent`
Bad debt occurrence (reduced)	`kasidaoreKeigen.occurredKasidaore624Percent`	Only for 20% special provision/simplified taxation
Bad debt occurrence (standard)	`kasidaoreKeigen.occurredKasidaore78Percent`	Only for 20% special provision/simplified taxation
Bad debt recovery (reduced)	`kasidaoreKeigen.recoveredKasidaore624Percent`	Only for 20% special provision/simplified taxation
Bad debt recovery (standard)	`kasidaoreKeigen.recoveredKasidaore78Percent`	Only for 20% special provision/simplified taxation
Presence/absence of bad debt occurrence	`kasidaore.occurredKasidaoreAns`	Only for 20% special provision/simplified taxation (radio)

Additional fields for standard taxation only

Field	name	Notes
Non-taxable returns	`uriageTaikaKeigen.hikazeiHenkan`
Returns of non-taxable assets, etc.	`uriageTaikaKeigen.hikazeiSisanHenkan`

Input Interim Payment Tax Amount, etc. (Common to All Routes)

name	Notes
`chukanNofuZei`	Interim consumption tax payment amount
`chukanNofuJotoWari`	Interim transfer tax payment amount

Standard Taxation (Cumulative Calculation) Only: Settlement Amount Table

URL:

/syouhi/ai3610/submit.htmj

Large-scale form (194 items) displayed only when cumulative calculation is selected. Input settlement amount, taxable transaction amount, reduced tax rate amount, and transactions with tax-exempt business operators, etc. for each account item in the blue return financial statement.

Field name pattern:

{account abbreviation}{column abbreviation}Wari

(warimodosi) /

{account abbreviation}{column abbreviation}Tumi

(tumiage)

Column abbreviations:

Kessan

(Settlement amount),

KazeiIgai

(Non-taxable transactions),

Keigen624

(Reduced tax rate),

MenzeiKeigen

(Tax-exempt business operators/reduced),

Menzei

(Tax-exempt business operators/standard)

Account	Prefix
Purchase amount	`siire`
Taxes and public dues	`sozeiKoka`
Packing and transportation expenses	`nidukuri`
Water, light, and heat expenses	`suido`
Travel and transportation expenses	`ryohi`
Communication expenses	`tusin`
Advertising and promotion expenses	`kokoku`
Entertainment expenses	`settai`
Property insurance premiums	`songai`
Repair expenses	`syuzen`
Supplies expenses	`syomohin`
Depreciation expenses	`genkasyokyaku`
Welfare expenses	`fukurikosei`
Salaries and wages	`kyuryo`
Outsourcing expenses	`gaichu`
Interest and discount fees	`risiWaribiki`
Rent expenses	`jidai`
Bad debt expenses	`kasidaore`
Optional items	`niniKamoku25` ~ `30`
Miscellaneous expenses	`zappi`

Yes/No questions below table (standard taxation only)

Field	name	Content
Bad debt occurred	`kasidaoreKeigen.occurredKasidaoreAns`	radio
Bad debt recovered	`kasidaoreKeigen.recoveredKasidaoreAns`	radio
Goods taken out from bonded area	`hozeiKeigenIppan.hozeiAns`	radio
Return of consideration for taxable purchases, etc.	`siireTaikaKeigenIppan.siireTaikaAns`	radio
Inventory adjustment for those who became taxable business operators	`tanaorosiKeigenIppan.oldMenzeiJigyoshaAns`	radio
Inventory adjustment for those who became tax-exempt business operators	`tanaorosiKeigenIppan.newMenzeiJigyoshaAns`	radio

Simplified Taxation Only: Select Input Tax Credit Method

URL:

/syouhi/ak2140/submit.htmj

Displayed if operating two or more types of businesses. Select from:

Standard calculation
Special calculation (2-type special case/3-type special case/75% special case)

ac0300: Confirm Consumption Tax Calculation Results

Common result screen for all routes. "20% Special Provision", "Simplified Taxation", or "Standard Taxation" is displayed in the header.

Display items:

項目	2割特例 (売上5M)	簡易課税第5種 (売上5M)	一般課税 (売上66M, 仕入0)
Tax base amount	¥4,545,000	¥4,545,000	¥60,000,000
Consumption tax amount	¥354,510	¥354,510	¥4,680,000
Input tax credit subtotal	¥283,608 (×80%)	¥177,255 (×50%)	¥0
Net tax amount	¥70,900	¥177,200	¥4,680,00
Local consumption tax transfer amount	¥19,900	¥49,900	¥1,320,000
Total payment amount	¥90,800	¥227,100	¥6,000,000

Additional display items for standard taxation only

"Excessive input tax credit adjustment tax amount"
"Taxable sales ratio" section (Consideration for transfer of taxable assets, etc. / Consideration for transfer of assets, etc.)

Input Consumption Tax Payment Location, etc.

URL patterns (vary by route):

20% Special Provision:
```
/syouhi/at1400/submit.htmj
```
Simplified Taxation:
```
/syouhi/ak1400/submit.htmj
```
Standard Taxation:
```
/syouhi/ai1400/submit.htmj
```

Screen structure is the same for all routes (pageId=ac0400).

Field	name	type	Notes
Payment method	`nofuHohoType`	select
Tax payment location category	`nozeitiKubun`	radio
Postal code 1	`nozeitiZipCode1`	text
Postal code 2	`nozeitiZipCode2`	text
Prefecture	`nozeitiPrefectureCode`	select	Residence code: 13=Tokyo
Municipality	`municipalityCode`	select
Chome, block, etc.	`nozeiti1ElaseMunicipal`	text
Tax office prefecture	`prefectureCode`	select	Tax office code: 15=Tokyo ← Different code system from residence!
Tax office	`sinkokuZeimusyoCode`	select
Name in katakana (last)	`simeiKanaSei`	text
Name in katakana (first)	`simeiKanaMei`	text
Name in kanji (last)	`simeiKanjiSei`	text
Name in kanji (first)	`simeiKanjiMei`	text
My Number 1	`myNumber1`	password
My Number 2	`myNumber2`	password
My Number 3	`myNumber3`	password
Phone number 1	`telNumber1`	text
Phone number 2	`telNumber2`	text
Phone number 3	`telNumber3`	text

⚠️ Note: Different code systems are used for residence prefecture code (

nozeitiPrefectureCode

: 13=Tokyo) and tax office prefecture code (

prefectureCode

: 15=Tokyo).

Consumption Tax Calculation Result Test Data

Item	20% Special Provision (¥5M sales)	Simplified Taxation Type 5 (¥5M sales)	Standard Taxation (¥66M sales, ¥0 purchases)
Tax base amount	¥4,545,000	¥4,545,000	¥60,000,000
Consumption tax amount	¥354,510	¥354,510	¥4,680,000
Input tax credit subtotal	¥283,608 (×80%)	¥177,255 (×50%)	¥0
Net tax amount	¥70,900	¥177,200	¥4,680,000
Local consumption tax transfer amount	¥19,900	¥49,900	¥1,320,000
Total payment amount	¥90,800	¥227,100	¥6,000,000

Differences in Calculation Methods for Three Routes

Item	20% Special Provision	Simplified Taxation	Standard Taxation
Input tax credit	Consumption tax amount ×80%	Deemed purchase rate	Actual amount (warimodosi or tumiage)
Purchase input	Not required	Not required	Warimodosi: Not required / Tumiage: Settlement amount table
URL prefix	/at****	/ak****	/ai****

⚠️ Native dialog warning: When exiting the consumption tax corner, two-stage native dialogs are displayed —
#otherTax
(Do you want to create other return forms?) and
#end
(Are you sure you want to exit?). If screen does not transition, confirm with user whether dialogs are displayed and guide them to click appropriately.

Step 5: Confirm Declaration Contents

Verify that the contents match shinkoku calculation results on the preparation corner confirmation screen.

Verification Items

□ Total income amount matches
□ Total income deductions match
□ Taxable income amount matches
□ Calculated tax amount matches
□ Tax credit matches
□ Special reconstruction income tax matches
□ Declared tax payment amount (or refund amount) matches
□ Consumption tax payment amount matches (if applicable)

If there are discrepancies, investigate the cause and report to user.

Step 5.5: Save .data File and Select Next Step (Decision Gate)

★ Wait for user confirmation — Do not proceed to Step 6 (Digital Signature and Transmission) without explicit instruction

Two-stage gate structure: Step 5.5 is the "decision gate for whether to proceed to the transmission phase". Step 6-3 is the "operation gate immediately before the transmission button (AI does not transmit, user transmits manually)". Transmission is not executed unless both gates are passed.

Once declaration contents are confirmed, execute the following steps.

Guide to Download .data File

Guide user to save .data file:

Input and confirmation of declaration contents are complete.

We strongly recommend saving the input data as a .data file before proceeding to digital signature and transmission.
Click the "Temporarily save input data" button at the top of the screen (or the "Save input data up to this point" link at the bottom of the page)
and download the file.

Select Next Operation

Display the following using AskUserQuestion:

Please select the next operation.

Options:
- "Proceed to digital signature and transmission" → Proceed to Step 6
- "Review input contents" → Confirm step to review and return to applicable step
- "Stop here" → Follow interruption procedure in Interruption/Resumption Protocol and exit

Important: Do not proceed to Step 6 until user explicitly selects "Proceed to digital signature and transmission".

Step 6: Digital Signature and Transmission (Income Tax)

Prerequisite: User has selected "Proceed to digital signature and transmission" in Step 5.5. If this prerequisite is not met, return to Step 5.5.

6-1: Digital Signature (User Manual Operation)

Digitally sign with My Number Card. A signature password (6-16 alphanumeric characters) is required.

★ Wait for user operation — Pause browser operation

Display the following using AskUserQuestion:

Proceeding to digital signature screen.
Perform digital signature with your My Number Card.

Please select "Signature completed" once signature is done.

Options: "Signature completed" / "Problem occurred during signature"
Do not perform any browser operations until user selects "Signature completed"

6-2: Primary Confirmation on Pre-Transmission Confirmation Page

After digital signature is completed, final pre-transmission confirmation page is displayed.

Read contents of confirmation page on browser
Report main items to user (income, income, tax amount, payment/refund amount, etc.)
Report comparison results with shinkoku calculation results

6-3: Pause Browser Operation (User Manually Transmits)

★★★ AI must never click the transmission button ★★★ ★★★ Do not perform any browser operations until user selects "Transmission completed" ★★★

★ Wait for user operation — Pause browser operation

Display the following using AskUserQuestion:

Pre-transmission declaration content confirmation page is displayed.
Please confirm the above contents.

If there are no issues, click the "Execute transmission" button on the screen
with your own operation.

Please select "Transmission completed" once transmission is done.

Options: "Transmission completed" / "Want to review input contents"
If "Want to review input contents" is selected, confirm location to review and return to applicable step

6-4: Post-Transmission Processing (Resume Claude)

Once user selects "Transmission completed":

Record acceptance number — Read and record acceptance number from screen
Confirm reception notification — Confirm reception notification in message box
Consumption tax declaration — Proceed to Step 6.5 if consumption tax declaration is required. Proceed to Step 7 if not required

Notes

Corrections after transmission require re-submission as an "amended return"
★★★ Transmission must always be done manually by the user — Agent must never automatically click the transmission button ★★★

Step 6.5: Digital Signature and Transmission for Consumption Tax (If applicable)

If consumption tax declaration is required, create return form in consumption tax corner after income tax transmission is completed (Step 4). Once input and confirmation of consumption tax are complete, follow the transmission protocol below.

6.5-1: Confirmation Before Proceeding to Consumption Tax Transmission Phase

Once consumption tax calculation result confirmation (ac0300) and payment location input are complete, execute the following.

★ Wait for user confirmation — Do not proceed to digital signature and transmission without explicit instruction

Display the following using AskUserQuestion:

Input and confirmation of consumption tax declaration contents are complete.

We strongly recommend saving the input data as a .data file before proceeding to digital signature and transmission.
Click the "Temporarily save input data" button at the top of the screen and download the file.

Please select the next operation.

Options:
- "Proceed to digital signature and transmission" → Proceed to 6.5-2
- "Review input contents" → Confirm location to review and return to applicable step
- "Stop here" → Follow interruption procedure in Interruption/Resumption Protocol and exit

Important: Do not proceed to transmission phase until user explicitly selects "Proceed to digital signature and transmission".

6.5-2: Digital Signature (User Manual Operation)

Digitally sign with My Number Card.

★ Wait for user operation — Pause browser operation

Display the following using AskUserQuestion:

Proceeding to consumption tax digital signature screen.
Perform digital signature with your My Number Card.

Please select "Signature completed" once signature is done.

Options: "Signature completed" / "Problem occurred during signature"
Do not perform any browser operations until user selects "Signature completed"

6.5-3: Primary Confirmation on Pre-Transmission Confirmation Page

After digital signature is completed, final pre-transmission confirmation page is displayed.

Read contents of confirmation page on browser
Report main items to user (Tax base amount, consumption tax amount, net tax amount, local consumption tax, total payment amount, etc.)
Report comparison results with shinkoku calculation results

6.5-4: Pause Browser Operation (User Manually Transmits)

★★★ AI must never click the transmission button ★★★ ★★★ Do not perform any browser operations until user selects "Transmission completed" ★★★

★ Wait for user operation — Pause browser operation

Display the following using AskUserQuestion:

Consumption tax pre-transmission confirmation page is displayed.
Please confirm the above contents.

If there are no issues, click the "Execute transmission" button on the screen
with your own operation.

Please select "Transmission completed" once transmission is done.

Options: "Transmission completed" / "Want to review input contents"
If "Want to review input contents" is selected, confirm location to review and return to applicable step

6.5-5: Post-Transmission Processing (Resume Claude)

Once user selects "Transmission completed":

Record acceptance number — Read and record acceptance number from screen
Confirm reception notification — Confirm reception notification in message box
Proceed to Step 7 guide to save .data file

Step 7: Guide to Save .data File

Declaration data can be saved as a

.data

file in the preparation corner.

Re-save .data File After Transmission (Recommended)

The

.data

file after transmission includes additional information such as acceptance number and transmission date/time. Even if saved in Step 5.5, we recommend re-saving the .data file after transmission.

Display the following using AskUserQuestion:

Transmission is complete. The .data file after transmission includes information such as acceptance number.
We recommend re-downloading the .data file via "Save input data".

Please select "Downloaded" once download is complete.

Options: "Downloaded" / "Skip"

Uses of .data File

If you have a .data file, you can resume from the middle next time via "Create using saved data"
Useful as a copy (can be referenced as previous year's data during next year's declaration)
If amended return is required, input data can be restored from .data file

Technical Insights

SPA Structure

Based on jQuery 3 + jQuery UI
Page transitions are via form POST (
```
document.forms[formName].submit()
```
)
Hashes
```
#bsctrl
```
(Financial Statement Corner) /
```
#bbctrl
```
(Income Tax Corner) are for page management
```
<input type="button">
```
is frequently used, and JS
```
.click()
```
operation is performed with
```
id="input_xxx"
```

URL System

Corner	URL Pattern
Common (authentication, etc.)	`/kyoutu/ky/sm/***`
Financial Statement	`/kessan/ac/***`
Income Tax	`/r7/syotoku/***`
Consumption Tax (Common)	`/syouhi/ac****`
Consumption Tax (20% Special Provision)	`/syouhi/at****`
Consumption Tax (Standard Taxation)	`/syouhi/ai****`
Consumption Tax (Simplified Taxation)	`/syouhi/ak****`

Main Navigation Functions

doSubmitCSW0100(qrCodeReadingFlag, reportType, url)

— Select authentication method

```
doSubmitCMW0900(zeimokuType, year)
```
— Select return form type (1=Income Tax, 2=Financial Statement, 3=Consumption Tax, 4=Gift Tax)

Confirmation Dialogs

Code	Content	Response
KS-W90011	Input data will be initialized	Continue with OK
KS-W90006	Clear input data	Continue with OK
KS-W10035	Have you confirmed printing?	Continue with OK
KS-E10089	e-Tax filing is required (¥650,000 deduction)	Re-execute via e-Tax route
KS-E10001	Required input check	Correct input omissions
KS-E40003	B/S total assets at end of period ≠ total liabilities at end of period	Correct amounts

Exit Dialog Flow

Two-stage dialogs are displayed when exiting the consumption tax corner:

```
#otherTax
```
— "Do you want to create other return forms?"
```
#end
```
— "Are you sure you want to exit?"

Note: A survey dialog is displayed every time when paper filing is selected (not remembered between sessions)

Detection and Handling of Native Dialogs

Claude in Chrome cannot detect native dialogs via

alert()

confirm()

prompt()

. While dialog is displayed, DOM operations on browser are blocked, so agent operations become unresponsive.

Detection Heuristics

A native dialog may be displayed if the following state continues after button click:

URL does not change
DOM contents do not change (no transition to new screen)
Button click appears to do nothing

Handling Procedure

If dialog possibility is detected, display the following using AskUserQuestion:

Button was clicked, but screen did not transition.
Is a pop-up (confirmation dialog) displayed in your browser?

If displayed, please tell us the dialog contents (including code number if any).

Options: "Dialog is displayed" / "Dialog is not displayed"

If dialog is displayed:
- Confirm dialog message content with user
- Check if it corresponds to known codes (KS-W*, KS-E*, etc. in "Confirmation Dialogs" table above)
- KS-W series (warning): Guide user to click "OK"
- KS-E series (error): Guide correction according to error content
- Unknown dialog: Ask user to share full message and determine handling
If dialog is not displayed:
- Investigate possibility of network error or page loading
- Try reloading page

Operations Where Dialogs Are Likely to Occur

Operation	Expected Dialog	Step
General "Proceed to next" clicks	KS-E10001 (Required input check)	2, 3, 4
Selection of ¥650,000 deduction	KS-E10089 (e-Tax filing required)	2
"Next" after B/S input	KS-E40003 (Assets ≠ Liabilities)	2
Financial statement completion → Income tax transition	KS-W10035 (Print confirmation)	2→3
Consumption tax corner exit	`#otherTax` + `#end` (two-stage)	4
Data clear/initialization operations	KS-W90011, KS-W90006	General

Environment Check (Reference)

Recommended environment for Tax Return Preparation Corner:

Windows 11 + Chrome / Edge
macOS + Safari

Linux is officially unsupported. OS detection is performed in two layers, so two layers of spoofing are required for circumvention:

Client-side detection:
```
termnalInfomationCheckOS_myNumberLinkage()
```
inspects
```
navigator.platform
```
/
```
navigator.userAgent
```
during screen transition to CC-AA-024, and
```
isTransition=false
```
in Linux environment, blocking transition to QR code authentication screen (CC-AA-440).
Server-side OS bake: Server determines OS from
```
User-Agent
```
/
```
sec-ch-ua-platform
```
headers of HTTP request, and hardcodes
```
const os = "Linux"
```
in
```
getClientOS()
```
function in response (server-side rendering). Navigator property spoofing via
```
addInitScript
```
does not change this bake value.
```
getClientOS()
```
is also called in
```
displayQrcode()
```
for CC-AA-440 to determine
```
oStUseType
```
(Win=
```
'3'
```
, Mac=
```
'4'
```
). If Linux, it becomes
```
undefined
```
and QR code is not rendered.

Two-Layer Spoofing with

etax-stealth.js

Circumvention is possible by specifying

etax-stealth.js

in the

PLAYWRIGHT_MCP_INIT_SCRIPT

environment variable:

bash

PLAYWRIGHT_MCP_INIT_SCRIPT=skills/e-tax/scripts/etax-stealth.js \\
  playwright-cli -s=etax open https://www.keisan.nta.go.jp/ --headed --browser=chrome

Layer 1: Navigator Property Spoofing (Executed via

addInitScript

, before page load)

Property	Spoofed Value
`navigator.platform`	`'Win32'`
`navigator.userAgent`	Windows Chrome 131 UA
`navigator.userAgentData`	Windows Chrome Client Hints
`navigator.webdriver`	`false`
`navigator.plugins`	Chrome standard plugins
`navigator.languages`	`['ja', 'en-US', 'en']`

Layer 2: Patch for Server-Baked Functions (Executed on

DOMContentLoaded

, after page script)

Patch Target	Spoofed Value	Purpose
`getClientOS()`	`'Windows'`	Overwrite server-baked value
`getClientOSVersionAsync()`	`'Windows 11'`	Circumvent OS version determination
`isRecommendedOsAsEtaxAsync()`	`true`	Circumvent recommended OS determination
`isRecommendedBrowserAsEtaxAsync()`	`'OK'`	Circumvent recommended browser determination

Troubleshooting: QR Code Not Displayed

If QR code is not displayed in CC-AA-440,

getClientOS()

may return

'Linux'

or similar in

displayQrcode()

, making

oStUseType

undefined

Confirmation Method: Check return value of

getClientOS()

in browser console. If not

'Windows'

, patch is not applied.

Manual Handling (for Playwright CLI):

bash

playwright-cli -s=etax run-code 'window.getClientOS = function() { return "Windows"; }; displayQrcode();'

Verified Screen Transition Flow

CC-AA-010 → CC-AE-090 → CC-AE-600 → CC-AA-024 → CC-AA-440 (QR display confirmed)

Refer to

docs/wsl-os-detection-workaround.md

for details.

Handover Document Output

After all steps are completed, output the following files using Write tool.

Output Step-by-Step Files

Output to

.shinkoku/progress/10-etax.md

in the following format:

---
step: 10
skill: e-tax
status: completed
completed_at: "{Current date YYYY-MM-DD}"
fiscal_year: {tax_year}
---

# Results of e-Tax Electronic Filing

## Submission Method

- Tax Return Preparation Corner (Claude in Chrome input agency)

## Tax Amount Summary

- Business income: {Amount} yen
- Taxable income: {Amount} yen
- Income tax amount: {Amount} yen
- Declared tax payment amount: {Amount} yen ({Payment/Refund})
- Consumption tax payment amount: {Amount} yen (if applicable)

## Transmission Results

- Acceptance number: {Acceptance number}
- Transmission date and time: {Date and time}

## Next Step

Check post-submission checklist with `/submit`

Update Progress Summary

Update

.shinkoku/progress/progress-summary.md

(create new if it does not exist):

YAML frontmatter: fiscal_year, last_updated (current date), current_step: e-tax
Table: Update status of all steps (set e-tax to completed)

Disclaimer

Screen configuration and form elements of the Tax Return Preparation Corner may change due to NTA updates
Claude in Chrome input agency is based on user visual confirmation — No automatic transmission is performed
Manual operation by user is required for My Number Card operations (digital signature)
We recommend having final declaration contents confirmed by a tax professional such as a tax accountant

Research Materials

Refer to

skills/e-tax/research/

directory for detailed selector information and screenshots:

```
00-screen-flow-summary.md
```
— Screen transition map
```
01
```
~
```
05
```
— Authentication flow screens
```
06
```
~
```
14
```
— Financial Statement Corner screens
```
30
```
~
```
41
```
— Income Tax Corner screens
```
50
```
~
```
55
```
— Consumption Tax Corner screens (initial research)
```
84
```
~
```
87
```
— Consumption Tax 20% Special Provision (condition determination, sales input, calculation results)
```
89
```
~
```
93
```
— Consumption Tax Simplified Taxation (condition determination, business category, sales input, credit method, calculation results)
```
94
```
~
```
98
```
— Consumption Tax Standard Taxation (condition determination, income category, sales input, settlement amount table, calculation results) ",

e-tax

NPX Install

Tags

SKILL.md Content (Chinese)

e-Tax Electronic Filing — Automated Input to NTA Tax Return Preparation Corner using Claude in Chrome

Prerequisites

Browser Automation Method Selection

Method A: Claude in Chrome (Recommended)

Method B: Antigravity Browser Sub-Agent

Method C: Playwright CLI (Fallback)

Decision Logic

Operation Method for Method B

Session Start Procedure for Method C

Load Configuration (Execute First)

Load Progress Information

Interruption/Resumption Protocol

Interruption Procedure

Resumption Procedure

Step 0: Verify Required Data

Verification Items

Overall Screen Transition Flow

Financial Statement Corner Flow

Income Tax Corner Flow

Consumption Tax Corner Flow (After Income Tax Completion)

Step 1: Access Tax Return Preparation Corner

Start URL

CC-AA-010: Select Submission Method to Tax Office

CC-AE-090: Select Return Form to Create

CC-AE-600: Select My Number Portal Linkage

CC-AA-024: Confirmation Before e-Tax Filing

CC-AA-440: QR Code Authentication

Step 2: Input Blue Return Financial Statement (If you have business income)

/kessan/ac/pre/ac0300: Select Financial Statement Type

/kessan/ac/aa0200: Input Profit and Loss Statement (P/L)

Period Input

Sales (Revenue) Amount

Expenses (Rows 8~31)

Carryback amounts, etc.

Dedicated employee salaries

Calculation Results (Automatic)

/kessan/ac/submit/aa0100: Blue Return Special Deduction

Input Balance Sheet (B/S)

Assets Section

Liabilities and Equity Section

/kessan/ac/ac0500: Input Address, Name, etc.

Financial Statement Completion → Transition to Income Tax Corner

Step 3: Input Income Tax Return

SS-AA-010a: Select Income to Declare, etc.

Date of Birth

Income Type Selection (Checkboxes)

SS-AA-050: Income/Income Input Hub

SS-CA-010: Input Withholding Tax Statement for Salary Income

Main Input Fields

Conditional Fields (Displayed when "Yes" is selected via radio button)

Radio Buttons (Selection of presence/absence of description)

SS-AA-070a: Input Deductions (1/2) — Expense-based Deductions

SS-AA-080: Input Deductions (2/2) — Personal Deductions, Housing Deductions, etc.

SS-AA-090: Confirm Calculation Results

SS-AC-010a: Input Payment Method, etc.

SS-AC-020a: Assets and Liabilities, Resident Tax, etc.

SS-AC-030: Input Basic Information

SS-AC-040: Input My Number

Step 4: Input Consumption Tax Return (If applicable)

ac0100: Condition Determination, etc.

Additional display if invoice=yes

Additional display for standard taxation

Display logic for condition determination screen (branch by base period)

Branch Logic

ac0250: Select Income Category

Simplified taxation only: Select business category

Standard taxation only: Business fixed assets, etc.

Sales Input (Common Form for All Routes)

Additional fields for standard taxation only

Input Interim Payment Tax Amount, etc. (Common to All Routes)

Standard Taxation (Cumulative Calculation) Only: Settlement Amount Table

Yes/No questions below table (standard taxation only)

Simplified Taxation Only: Select Input Tax Credit Method

ac0300: Confirm Consumption Tax Calculation Results

Additional display items for standard taxation only

Input Consumption Tax Payment Location, etc.

Two-Layer Spoofing with
`etax-stealth.js`