n8n Late Payment Dunning: Google Sheets + OpenAI + Gmail

Automate late-payment reminders from Google Sheets—powered by OpenAI and delivered via Gmail

This n8n Late Payment Dunning: Google Sheets + OpenAI + Gmail workflow reads your open invoices and payment history from Google Sheets every weekday morning, scores late-payment risk, and sends the right reminder tone—friendly, firm, or a follow-up call escalation with Slack.

What this workflow does

• Runs on a schedule: Executes at 9 AM on weekdays using an n8n schedule trigger.
• Loads your dunning rules: Pulls dunning thresholds and business settings, then reads invoice + payment history data from your Google Sheets workbook (e.g., Invoices and Payment History tabs).
• Scores each unpaid invoice: Calculates a per-client payment profile and assigns a 0–100 late-payment risk score for every open invoice.
• Selects a dunning tone: Chooses a reminder type (friendly, firm, or call) and applies cooldown rules so reminders don’t repeat too frequently or soften unintentionally.
• Drafts emails with OpenAI: Uses OpenAI (gpt-4o-mini) to generate a short pre-due/gentle overdue email for friendly reminders, or a clear overdue notice for firm reminders.
• Sends via Gmail: Dispatches the generated message using n8n’s Gmail integration.
• Escalates calls with Slack: For call items, appends a row to the Google Sheets “Call Tasks” tab and posts an escalation to Slack #collections.
• Logs outcomes back to Google Sheets: Updates each invoice row with the latest reminder stage, reminder date, and risk score for accurate follow-up tracking.

Use cases

• Reduce DSO by sending consistent, risk-based dunning emails to customers with overdue invoices.
• Escalate high-risk accounts from email to a call workflow with Slack notifications.
• Keep your collections process auditable by writing every reminder stage back to Google Sheets.

Technical details

• n8n schedule trigger (weekday mornings at 9 AM)
• Nodes used: if, set, code, gmail, slack, filter
• Integrations: Google Sheets, OpenAI (gpt-4o-mini), Gmail, Slack