Invoice Readiness Automation: Gmail to Google Sheets via n8n

Turn invoice emails into approved AP entries—automatically

Invoice Readiness Automation: Gmail to Google Sheets via n8n monitors your Gmail for incoming invoice emails, extracts structured data from attached invoice PDFs using Groq LLMs, validates each invoice against Purchase Orders in Google Sheets, predicts rejection risk with an LLM, and then emails suppliers or logs results for your AP workflow—so fewer invoices get stuck in manual review.

What this workflow does

• Triggers every minute when a new invoice email arrives in Gmail.
• Downloads the attachment and extracts text from the invoice PDF.
• Runs a Groq LLM extraction chain to convert invoice content into structured JSON, including invoice/PO/GRN numbers, supplier details, currency, totals, and line items.
• Validates against Google Sheets: looks up the referenced PO in a PurchaseOrders table.
• Rejects early when needed: if no matching PO is found, it rejects the invoice via Gmail.
• Performs integrity checks (required fields, non-zero amounts, and PO status is Approved) and emails the supplier if validation fails.
• Applies 3-way match rules (supplier, amount, currency, PO approval, and GRN presence) to classify status as APPROVED, FLAGGED, or REJECTED.
• Uses an LLM to predict rejection risk; if risk is HIGH, it emails the supplier a pre-submission warning.
• Routes outcomes: approved invoices are logged to an AP tracking Google Sheet; non-approved invoices trigger a Gmail alert for manual review.

Use cases

• AP teams receiving invoices in email who need automated PO validation and 3-way matching.
• SaaS operators standardizing invoice intake to reduce supplier back-and-forth.
• Automation engineers building a Gmail-to–Google Sheets approval pipeline using n8n + Groq LLMs.

Technical details

• n8n nodes: gmail, merge, code, set, if, sticky note
• LLM extraction & risk: Groq LLM chain produces structured JSON and rejection-risk predictions.
• Data stores: Google Sheets tables for PurchaseOrders and AP logging.