n8n Invoice Drafts from Chat or Forms w/ Claude & Google Workspace

Generate polished invoice drafts in minutes—automatically from Chat or Forms (Claude + Google Workspace)

This n8n workflow turns an invoice request from n8n Form or Google Chat into a PDF invoice using a Google Docs template, then creates a Gmail draft with the PDF attached. It also logs each invoice in Google Sheets for traceability.

What this workflow does

• Receives an invoice request via an n8n Form submission or a Google Chat webhook event.
• Validates Google Chat access by checking the sender email against an allowlist—responding with help text or an access error if unauthorized.
• Extracts customer and month by loading the Customers, Items, and Invoices tabs from Google Sheets and sending the customer list plus the request text to Anthropic Claude.
• Verifies extracted details, then calculates invoice lines, totals, tax, due date, and an invoice number using the Google Sheets data.
• Prevents bad outputs by stopping with an error if required data is missing, amounts are invalid, there are too many lines, or the invoice number already exists (unless marked void).
• Creates the invoice PDF by copying a Google Docs template in Google Drive, replacing placeholders via the Google Docs API, exporting to PDF, and preparing the final document.
• Drafts the email in Gmail to the customer with the PDF attached, and returns a form completion page or a Google Chat reply including the document link.
• Logs the invoice by appending a row to the Invoices tab in Google Sheets.

Use cases

• SaaS and service teams generating recurring invoices from customer requests without manual document edits.
• Operations workflows where staff message requests in Google Chat and receive an invoice link and email draft automatically.
• Automated invoicing for businesses that maintain customer, item, and invoice numbering in Google Sheets.

Technical details

• Integrations include Google Workspace (Google Sheets, Google Drive, Google Docs, Gmail) and Anthropic Claude.
• n8n nodes/features referenced: if, set, code, form, gmail, webhook.