n8n Invoice Follow-Up Automation: Gmail + Google Sheets

Never miss an invoice follow-up—automatically

This n8n automation scans your unpaid invoices in Google Sheets, sends Gmail reminders for due-soon and overdue items, logs every follow-up, escalates high-risk cases to your finance owner, and emails a weekly payment digest to keep receivables under control.

What this workflow does

• Daily (9am) invoice follow-ups: The workflow runs every day at 9am and reads invoices marked Unpaid from the Google Sheets Invoices tab.
• Stage-aware reminders: It calculates days until due/overdue, determines the correct reminder stage (due-soon vs overdue) and whether escalation is needed, then prepares the email subject and body for each actionable invoice.
• Send via Gmail: For invoices that require follow-up, it emails the client using Gmail.
• Log reminders in Sheets: Every sent reminder is appended to the Reminder Log tab, including overdue days, stage, email subject, and recommended action.
• Escalate high-risk invoices: For invoices flagged for escalation (e.g., final notice or high-value overdue), the workflow appends an entry to the Escalation Log tab and emails the finance owner with invoice details and the reason.
• Weekly (Monday 9am) digest: Every Monday at 9am, it reads unpaid invoices again, generates a receivables summary (due soon, overdue, high-risk), and emails the digest to the finance owner via Gmail.

Use cases

• Freelancers who want reliable, automated reminders without manually tracking due dates.
• Agencies managing multiple clients and needing consistent escalation for overdue invoices.
• Small finance teams that want weekly visibility into receivables and overdue risk.

Technical details

• Integrations/nodes: Google Sheets, Gmail, Schedule Trigger, if, and code.
• Workflow logic: Schedule-based runs (daily and weekly), conditional routing for escalation, and email composition per invoice.
• Required Google Sheets tabs: Invoices, Reminder Log, and Escalation Log (with expected columns such as Invoice ID, Client Email, Amount, Currency, Due Date, Status, and Last Reminder Date).