n8n Workflow: Sequential PDF Invoices from Google Sheets

Automatically generate, number, and email gapless PDF invoices from your Google Sheets ledger

This n8n workflow scans your Google Sheets invoice ledger every 15 minutes, verifies sequential Invoice No numbering with no gaps or duplicates, fills a Google Docs invoice template, exports it to a PDF from Google Drive, and emails it to customers via Gmail—while updating each row status as it goes.

What this workflow does

• Runs every 15 minutes and reads all rows from your Google Sheets invoice spreadsheet.
• Audits Invoice No sequences to ensure each series is sequential with no gaps, duplicates, or invalid formats. If issues are detected, processing stops.
• Sends an alert email via Gmail listing numbering problems so you can correct the ledger immediately.
• For rows marked Status = Ready (and missing invoice numbers), it calculates subtotal, tax, and total, validates required fields, and either:
  • Reserves the next sequential invoice number by writing Invoice No, Issued at, Total, and Numbered back to Google Sheets, or
  • Flags the row as incomplete with Needs details and the validation reason—without consuming an invoice number.
• Generates the invoice PDF: copies a Google Docs invoice template from Google Drive, replaces placeholders with invoice data, exports it as a PDF, and emails it as an attachment via Gmail.
• Updates status to Sent in Google Sheets and stores a link to the generated document.

Use cases

• Turn a Google Sheets ledger into a reliable, sequential invoice system with automated PDF delivery.
• Prevent numbering mistakes by enforcing gapless Invoice No sequences and alerting on ledger inconsistencies.
• Handle “Ready” invoices continuously without manual template editing or export steps.

Technical details

• Workflow category: n8n automation workflow
• Nodes / integrations: if, code, gmail, google docs, sticky note, google drive
• Required setup: connect Google Sheets, Google Drive, Google Docs, and Gmail credentials.