How to send overdue invoice reminders with an AI agent that adjusts its tone (n8n)

Finance & invoicingn8n

The problem

Chasing late payments is awkward. Reminders should be gentle for a few days overdue and firmer after weeks, and nobody wants to write each one.

Tools needed

• n8n (self-hosted in Docker in the source)
• Gemini (gemini-2.0-flash-lite)
• n8n Data Table
• Gmail SMTP

Step-by-step recipe

1. Keep invoices in an n8n Data Table: client, email, amount, due date, balance, status.
2. Create a chat-triggered AI agent with simple memory and two tools: one that reads the invoices table and one that sends email.
3. In the system prompt, tell it to select invoices that are past due, have a positive balance and are Pending, and to skip ones already Reminded.
4. Have it soften or firm up the tone depending on how many days overdue each invoice is.
5. Return a JSON summary of the emails sent.

Copyable prompt

You write payment reminders for [COMPANY]. For each invoice provided, write a short email to the client.
Tone by days overdue: 1-7 friendly reminder; 8-30 polite but clear, restate amount and due date; 31+ firm, mention next steps [NEXT STEPS].
Always include invoice number, amount, due date and how to pay: [PAYMENT DETAILS]. Never threaten, never add fees that are not in our terms.
Return JSON: [{"invoice": "...", "to": "...", "subject": "...", "body": "..."}]

What the builder reported

The source describes a finished workflow that runs from a single chat command. It reports no test results or example outputs.

These are the source author's own claims. AgentRecipes has not tested or verified them.

Watch out for

• Gmail SMTP sending needs an app password.
• The source doesn't update the status to Reminded after sending; add that step or clients will get duplicate reminders.
• The agent filters rows itself from a full-table fetch; for larger tables, filter in a normal node first.

Source

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