Gmail Invoice Email to Google Sheets + Slack Reminder (n8n)

Turn Gmail invoice PDFs into a live Google Sheets ledger—then auto-remind finance in Slack

This n8n workflow watches your Gmail for newly labeled invoice emails, extracts invoice details from attached PDFs using OpenAI (GPT-4o), appends the structured data to Google Sheets, and automatically sends a payment reminder email—followed by an escalation message in your Slack #finance channel.

What this workflow does

• Monitors Gmail every minute for new messages that have the INVOICES label.
• Extracts text from the invoice PDF attachment in the email.
• Uses OpenAI (GPT-4o) to parse the extracted text into structured invoice fields: vendor, invoice number, amount, currency, and due date.
• Appends the invoice data to a Google Sheets accounting ledger (ledger-style worksheet for tracking).
• Evaluates a score value and, when it meets your configured threshold, sends a payment reminder email to the defined recipients.
• Posts an escalation message to Slack right after the reminder email is sent, helping your finance team respond faster.

Use cases

• Accounts payable teams who receive vendor invoices by email and want automatic entry into a Google Sheets ledger.
• SaaS operators managing recurring billing/vendor payments and needing due-date reminders with Slack escalation.
• Automation engineers deploying an n8n workflow that bridges Gmail + PDF parsing + OpenAI + Google Sheets + Slack for invoice ops.

Technical details

• Gmail trigger: runs every minute for emails with the INVOICES label.
• Email/PDF processing: extracts text content from the email’s PDF attachment.
• OpenAI (GPT-4o): converts unstructured PDF text into structured invoice fields.
• Google Sheets: append operation to your target spreadsheet and worksheet.
• Email send: sends payment reminder messages to configured recipients.
• Slack: posts to your finance channel (e.g., #finance), including an escalation message after the reminder email.

Setup in a nutshell

Connect Gmail (ensure invoices have the INVOICES label), add an OpenAI credential (confirm GPT-4o access), configure Google Sheets append targets, set email-sending credentials and reminder recipients, and connect Slack with the correct finance channel.