Gmail Invoice PDF to Google Sheets (n8n + GPT-4.1-mini)

Turn Invoice PDFs in Gmail into Structured Rows in Google Sheets—Automatically

This Gmail Invoice PDF to Google Sheets (n8n + GPT-4.1-mini) workflow scans your Gmail inbox for invoice emails with PDF attachments, extracts the invoice text, uses OpenAI (gpt-4.1-mini) to convert it into structured fields, normalizes the data, and appends each invoice into a Google Sheets tracker—ready for reporting and bookkeeping.

What this workflow does

• Runs on a schedule (every hour) and searches Gmail for messages with attachments matching invoice OR bill OR receipt.
• Processes attachments individually: it skips emails with no attachments and splits emails so each PDF attachment is handled separately.
• Extracts PDF text from each attachment.
• Uses an AI Agent to structure invoices: sends the extracted text to gpt-4.1-mini to return invoice data as JSON.
• Normalizes the output into a consistent schema (e.g., invoice number, dates, vendor details, totals, and tax) and converts numeric values.
• Appends to Google Sheets using invoice_number as the matching column.

Use cases

• SaaS operators tracking recurring vendor invoices without manual copy/paste.
• Automation engineers building an invoice intake pipeline from Gmail attachments to a spreadsheet-based ledger.
• Finance teams consolidating invoice numbers, dates, tax, and totals into a single Google Sheets dashboard.

Technical details

• n8n Gmail Trigger to poll Gmail hourly.
• if and code nodes for attachment checks, splitting, JSON parsing, normalization, and numeric conversion.
• n8nn8n-nodes-langchainagent AI Agent using OpenAI gpt-4.1-mini to transform PDF text into structured invoice JSON.
• Google Sheets integration to append normalized invoice records to the selected spreadsheet and sheet.
• Optional setup notes: align Google Sheets headers with appended fields (e.g., invoice_number, date, due_date, vendor_name, subtotal, tax, and totals).