Chasing money is the job nobody wants. Each weekday this checks your invoice sheet and drafts a reminder for anything overdue, friendly at first, firmer later. After about a month it stops writing and tells you the invoice needs a phone call. It never mentions fees, collections or legal action.
Import it into n8n
The short lesson
- Why it matters
- Invoices tend to get paid sooner when reminders are routine and friendly, because they stop feeling personal.
- Common mistake
- Going harsh too soon, or letting the AI mention fees or legal steps. Stay polite until a person decides otherwise.
- Next step
- Sync with your accounting software so a paid invoice stops reminders straight away.
What's inside
- An n8n workflow that reminds clients about overdue invoices
- Three tones by age, then a 'call this one' alert to you
- It tracks reminders on the sheet and waits between them
- The prompt, to use in any other tool
What it does
- Each weekday morning it reads your invoice sheet.
- It finds unpaid invoices past their due date that are due for another reminder.
- Recent ones get a friendly note, a week or more gets a firm one, three weeks or more gets a final clear one.
- Past 30 days, or with no email on file, it skips writing and emails you that the invoice needs a call.
- Reminders are saved as Gmail drafts, or sent once you turn auto-send on. The sheet is updated.
Set it up
Pick the path that matches the tools you already use.
- Download the workflow file from the box on this page. It's a .json file.
- In n8n, create a new workflow, open the ⋯ menu at the top right, and choose Import from file. Pick the file you downloaded.
- Nodes that need a login show a warning. Click each one and connect your own account. n8n walks you through it.
- Open the node called Settings and replace the sample values with yours.
- Click Execute workflow to run it once with test data and check what comes out.
- When you're happy with it, switch the workflow to Active.
| You'll connect | What it's used for |
|---|---|
| Google Sheets | Holds your invoices and tracks reminders |
| Gmail | Drafts or sends the reminder, and emails you the call alerts |
| An AI model | Writes each reminder |
| Google Sheet: Invoices |
|---|
| Invoice # · Customer · Email · Amount · Due Date · Paid Date · Reminders Sent · Last Reminder |
Fill in Paid Date when an invoice is paid and it stops. Use real dates.
Using Claude, Gemini or another model instead of OpenAI? Delete the model node under each AI step, add the one you want, and drag its connector into the AI step.
New to n8n? Start here →The AI prompt
This is exactly what the n8n file sends to the AI. Square brackets are the details your tool fills in for each customer.
Instructions to the AI
You write payment reminder emails for [business]. Tone by level: - friendly: a few days late. Assume it slipped through. - firm: a week or more late. Polite and clear. - final: three weeks or more late. Clear that you would like to settle it this week or talk about it. Rules: - Under 90 words. Include the invoice number and the amount. - Never threaten. Never mention collections, fees, interest or legal action. Never invent a late fee. Return only JSON with the keys "subject" and "body".
What you send it each time
Customer: [name] Invoice number: [invoice] Amount: [amount] Due date: [dueDate] Days late: [daysLate] Level: [level] How to pay: [payInstructions] Sign off as [owner], [business].
Test it before it touches a customer
- Add four test invoices with your email: three days late, ten days late, thirty-five days late, and one already paid.
- Check the tones step up, the old one becomes a call alert, and the paid one is ignored.
- Read the drafts for anything that sounds like a threat. There shouldn't be any.
Start with auto-send off. You get drafts in Gmail to read and send yourself. After you've read ten and they sound like you, turn auto-send on.
When you'll outgrow this
This is the right size for most small businesses. These are the signs it's time for something sturdier.
- Invoices live in accounting software and you want reminders and payments to sync automatically.
- You need payment links, partial payments or payment plans handled inside the reminders.
- Your terms differ by customer and the rules have become hard to keep straight.