n8n Workflow: Send Overdue Invoice Reminders via Gmail + Sheets

Automate overdue invoice reminders with Gmail + Google Sheets in n8n

This n8n workflow automatically checks your open invoices in Google Sheets every weekday and sends staged overdue payment reminders via Gmail—then emails a weekly receivables aging report to your finance inbox and logs each reminder stage back in the sheet.

What this workflow does

• Runs on a schedule: Executes every weekday at 9:00.
• Reads invoice data from Google Sheets: Loads all rows from the Invoices tab using unformatted values for consistent date handling.
• Calculates overdue status: For each invoice not marked Paid or Cancelled, it calculates days overdue.
• Sends the next unsent reminder stage: Selects the next reminder stage based on the overdue timeline (for example day 0, 7, 14) or triggers escalation when the escalation day is reached.
• Sends via Gmail: Sends reminder emails to the customer, or—when test mode is enabled—routes emails to the finance inbox. Escalations can be sent to an escalation contact for manual follow-up.
• Prevents duplicate sends: Updates the matching Google Sheets row with last_stage_sent and last_sent_at so the same stage isn’t sent twice.
• Sends weekly aging summary: On the configured weekday, builds a receivables aging summary (Not yet due, 0–30, 31–60, 61–90, 90+) and emails it to the finance inbox via Gmail.

Use cases

• Reduce payment delays by automatically emailing overdue invoice reminders on day 0, 7, and 14.
• Escalate long-overdue invoices to a dedicated contact without manual spreadsheet checks.
• Keep finance updated with a weekly receivables aging report generated from the same invoice source.

Technical details

• n8n schedule (weekday 9:00)
• Google Sheets nodes (Invoices tab; unformatted values)
• Gmail node for customer reminders, escalation emails, and weekly aging reports
• Nodes used: if, set, code, gmail, sticky note, google sheets

Setup: Create an Invoices tab with required columns (including invoice_id, due_date, status, last_stage_sent, last_sent_at), add Google Sheets and Gmail credentials in n8n, and select the target spreadsheet in the Google Sheets nodes.