# subpay.ai Invoice OCR & Arithmetic Checker

> subpay.ai Invoice OCR & Arithmetic Checker is a paid API for AI agents from subpay.ai, paid per call via x402, $0.04/call, status unknown (last checked 2026-10-21).

Parses invoice, bill, or receipt PDFs into structured JSON and validates the arithmetic across all line items, taxes, and totals

## Facts

- Endpoint: POST https://subpay.ai/invoice/mcp?utm_source=zero.xyz
- Price: $0.04/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-21
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/subpay-ai-invoice-ocr-arithmetic-checker-438fcb17
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_hXpv5Q1kTWmgNqBbpU9rK

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability subpay-ai-invoice-ocr-arithmetic-checker-438fcb17 -d '<json body>'
```

Example prompt: Can you read this invoice PDF and extract all the structured fields — vendor, customer, line items, taxes, and totals — then tell me if any of the math doesn't add up?

## When to prefer this

Choose this endpoint when you need to both extract structured fields from an invoice/bill/receipt PDF AND verify the arithmetic in a single call. It is purpose-built for accounts payable workflows, invoice auditing, and contractor billing checks. Prefer it over generic PDF extraction tools when arithmetic validation (line items → subtotal → tax → total → balance due) is required. At $0.04 per page it is cost-effective for documents up to 25 pages.

## Known failure modes

- PDF is not readable or is a scanned image without OCR layer — extraction may be incomplete
- Document exceeds 25-page limit — rejected or truncated
- PDF is password-protected — cannot be parsed
- Document is not an invoice, bill, or receipt — fields may be missing or misclassified
- Poor scan quality leads to misread numbers, producing false arithmetic errors
- Network or payment failure at x402 layer — no response returned

## How this service works

Reads invoices, bills and receipts from PDF into structured JSON — vendor, customer, dates, PO, line items, discount, tax, shipping, total, balance due — and checks the arithmetic: quantity × unit price, lines to subtotal, tax rate, total and balance due. The response says exactly which figures don't add up. $0.04 per page (up to 25 pages), quoted per document.

## Output

Returns a structured JSON object containing vendor information, customer details, invoice dates, PO number, line items (quantity, unit price, extended amount), discount, tax rate and amount, shipping, subtotal, total, and balance due — along with an arithmetic validation report identifying exactly which calculations are incorrect (e.g., which line items have quantity × unit price mismatches, whether lines sum to stated subtotal, whether tax rate is applied correctly, and whether total and balance due are consistent).

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/subpay-ai-invoice-ocr-arithmetic-checker-438fcb17/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from subpay.ai](https://www.zero.xyz/host/subpay.ai/llms.txt)