Stop Typing Invoices by Hand: An AI + n8n Workflow That Files Them for You

Description and use

Automated invoice ingestion with n8n and OpenAI, duplicate and total checks, posting to accounting software, review queue, and daily reminders.

Problem

Manual entry of supplier invoices consumes time and introduces errors, especially for small businesses handling dozens of invoices monthly.

Outcome

Invoices are processed automatically with high accuracy, reducing manual effort and error rates, while maintaining an audit trail and a review queue for anomalies.

Workflow

• Receive invoice file via webhook
• Validate file type
• Extract text with PDF OCR
• Run AI extractor to pull vendor, date, line items, totals
• Check for duplicate using Google Sheets log
• Validate extracted totals against line items
• If valid, post to accounting API (QuickBooks/Xero)
• If invalid or duplicate, send to review queue and email owner
• Log all invoices to Google Sheets
• Every morning at 8 AM email owner list of review‑queue invoices

Evidence

Every supplier invoice that lands on a small business owner's desk costs two things: the minutes it takes to type it into the books, and the mistakes that slip in while doing it.

Source

A webhook receives the uploaded invoice file. The workflow validates the file type, extracts the text with PDF OCR, and hands it to an AI information extractor that pulls out vendor, date, line items, and totals as structured fields.

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Duplicate check — the workflow looks the invoice up in a Google Sheets log. Already seen it? It goes to review instead of posting twice.

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Totals validation — the extracted line items are summed and compared against the extracted total. Mismatch? Review queue.

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Clean invoices post to your accounting software over HTTP (the QuickBooks/Xero endpoint you configure). Anything suspicious — duplicate, totals mismatch, unreadable file — lands in a human review queue and triggers an email alert to the owner.

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Every morning at 8 AM, the workflow emails the owner a list of invoices still sitting in review, so nothing gets forgotten.

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All credentials are placeholders you fill in yourself; nothing ships with real keys.

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