1. Receive and Parse Invoice Accept invoice data in any format — raw text, OCR output, structured JSON, or CSV. Identify the document type (standard invoice, credit memo, debit note, proforma) and extract the header block: invoice number, date, due date, vendor name, vendor address, and payment terms.
2. Extract Line Items and Totals Parse each line item for description, quantity, unit price, extended amount, and tax. Validate that line item totals sum to the stated subtotal. Extract tax amounts, shipping charges, discounts, and the grand total. Flag any arithmetic inconsistencies between line items and totals.
3. Validate Against Purchase Order Match the invoice to its corresponding PO by PO number, vendor, or line item descriptions. Compare quantities and unit prices. Compute a three-way match score across PO, goods receipt, and invoice. Flag invoices where price variance exceeds a configurable threshold (default: 2%) or quantities don't match.
4. Categorize by GL Code Assign each line item to the appropriate general ledger account based on item description, vendor category, and historical patterns. Common mappings include office supplies → 6200, software subscriptions → 6500, professional services → 6300, raw materials → 5100. Apply department cost center codes where applicable.
5. Flag Discrepancies and Generate Output Produce a structured record for each invoice with all extracted fields, validation status, GL assignments, and any flags. Group flags by severity: blocking errors (missing PO, total mismatch > 5%), warnings (minor price variance, missing fields), and informational (new vendor, first invoice from vendor).
6. Generate Processing Summary For batch operations, produce a summary report showing total invoices processed, pass/fail counts, total dollar value, and a breakdown of flag types. List all blocked invoices requiring manual review with specific reasons.

Process this vendor invoice: Invoice #INV-2024-0847 from Acme Cloud Services, dated 2024-11-15, PO #PO-4521. Line items: 10x API Gateway licenses at $150/ea, 1x Premium Support at $2,400/yr. Tax 8.5%. Validate against PO and assign GL codes.

• Total Processed: 4
• Passed: 1 (25%) — $4,231.50
• Warnings: 1 (25%) — $892.40
• Blocked: 2 (50%) — $20,095.00
• Total Value: $25,168.90
• Action Required: 2 invoices require manual review before payment authorization.

• Always verify arithmetic independently — never trust the stated totals without recalculating from line items.
• Maintain a vendor-to-GL mapping table and update it as new vendors or expense types appear.
• Set price variance thresholds appropriate to your industry: 2% for commodities, up to 10% for services with variable scope.
• Require PO matching for all invoices above a configurable dollar threshold to prevent unauthorized spending.
• Retain the raw invoice data alongside extracted fields for audit trail purposes.
• Process invoices in batch during off-peak hours and route exceptions to AP staff immediately.

• Invoices with no PO reference: Flag as requiring manual approval. Check if the vendor has a blanket PO or standing agreement that covers the charges.
• Credit memos and negative amounts: Process as negative invoice entries. Validate that the credit references an existing invoice and that the credit amount doesn't exceed the original.
• Multi-currency invoices: Extract the stated currency, apply the exchange rate as of invoice date, and record both the original and converted amounts.
• Duplicate invoice detection: Check invoice number + vendor + amount + date against the last 90 days of records. Flag exact matches as likely duplicates and near-matches (same vendor + amount, different invoice number) as potential duplicates.
• Partial shipments: When goods receipt quantity is less than PO quantity, validate the invoice against received quantity, not PO quantity. Hold remaining balance as open.