Automated Invoice Follow-Ups: Google Sheets + Gmail Reminders (n8n)

Automatically chase unpaid invoices—every morning—with Google Sheets + Gmail

This n8n workflow reads your invoice tracker in Google Sheets and automatically sends escalating Gmail reminder emails to clients based on how many days an invoice is overdue—then logs every reminder back to your sheet and alerts you when a tier-3 final notice is sent.

What this workflow does

• Runs daily at 9:00 using a Schedule Trigger.
• Reads all rows from the Invoices tab in your Google Sheet.
• Identifies unpaid invoices that are at least 3 days overdue and have not been emailed in the last 7 days.
• Assigns an escalation tier (tier 1, 2, or 3) based on overdue timing, and generates an email subject and body.
• Sends the reminder to the client using the Gmail node.
• Updates the same Google Sheets row with:
  • RemindersSent (incremented/count updated)
  • LastReminderDate
• If the reminder is a tier-3 final notice, it also sends an additional escalation alert to your own email via Gmail.

Use cases

• SaaS operators who want consistent invoice follow-ups without manually checking overdue payments.
• Freelancers and agencies using Google Sheets to track billing and letting n8n handle polite-to-final escalation.
• Automation engineers building a reliable invoice reminder workflow for recurring use.

Technical details

• Google Sheets: reads Invoices tab and updates Status, DueDate-related filters, ClientEmail, LastReminderDate, and RemindersSent.
• Gmail: sends client reminders and the tier-3 internal escalation alert.
• Schedule Trigger: runs every day at 9:00.
• if + code: applies the overdue/7-day cooldown logic and builds tiered email content.
• Sticky Note: workflow documentation within n8n.

Setup requires a Google account with access to your Google Sheet and Google/Gmail credentials in n8n.