Overdue Invoice Reminders That Sound Like You, Sent Only After You Approve Them
Quick verdict: if all you need is a polite, identical nudge a few days after the due date, turn on the reminder feature already built into QuickBooks Online or Xero and stop there. Build the AI workflow in this guide only when you want reminders that reference the specific client, invoice, and history, and that wait for your approval before they go out.
This guide is part of our AI Automation for Small Business series.
First, Check Whether the Built-In Reminder Is Enough
Both accounting tools already send reminders without any automation platform.
- QuickBooks Online: go to Settings, then Account and settings, then the Sales tab, and turn on automatic invoice reminders. You can schedule up to three reminders, each up to 90 days before or after the due date, and edit the email template for each one. See Intuit’s instructions.
- Xero: invoice reminders are a standard setting on sales invoices. Check Xero’s help centre for the current steps on your plan.
The built-in route costs nothing extra and takes about ten minutes. Its limit is that every client gets the same template. A client who has paid on time for three years and a client who is 45 days late on a second invoice receive the same words.
| Situation | Use the built-in reminder | Build the AI workflow |
|---|---|---|
| Fewer than 10 invoices a month | Yes | Not worth the setup |
| Same polite nudge suits every client | Yes | No |
| You want tone to change with how late the invoice is | Partly, with three templates | Yes |
| You want to read each reminder before it sends | No | Yes |
| You want reminders sent from your own inbox, in the original thread | No | Yes |
What You Need
- QuickBooks Online or Xero, with client email addresses on the customer records.
- A paid Zapier plan. The free plan allows only two-step Zaps and 100 tasks a month, and this workflow has six or seven steps. Professional starts at $19.99 a month billed annually ($29.99 billed monthly) for 750 tasks. See Zapier pricing.
- Gmail or Outlook connected to Zapier, so the reminder comes from you.
- About an hour for the first build and test.
The Workflow in One Picture
- An invoice goes overdue.
- Zapier re-checks that it is still unpaid.
- An AI step drafts a reminder using the client name, invoice number, amount, and days overdue.
- You get the draft by email or Slack and approve, edit, or decline it.
- If approved, it sends from your inbox. If declined, nothing sends.
- A row is added to a log so you can see what went out.
Step 1: Choose the Trigger
The two accounting tools expose different triggers in Zapier, so the first step differs.
Xero
Xero has a trigger called Overdue Sales Invoice, which fires when a sales invoice passes an overdue threshold you set. This is the simplest starting point. Set the threshold to the number of days you are comfortable waiting, for example 7. See the Xero triggers and actions in Zapier.
QuickBooks Online
QuickBooks Online has no “overdue” trigger in Zapier. The closest is New Invoice Due, which fires when an invoice becomes due within a number of days you specify. To turn that into an overdue reminder, add a Delay step after it, so the Zap waits until the invoice is, say, seven days past due before continuing. See the QuickBooks Online triggers and actions in Zapier.
Step 2: Re-Check That the Invoice Is Still Unpaid
This step is the one people skip, and it is the one that prevents an embarrassing email. Between the trigger and the send, the client may have paid.
- Add a Find Invoice action (both QuickBooks Online and Xero have one) using the invoice ID or number from the trigger.
- Add a Filter step that only continues when the balance due is greater than zero.
If the filter stops the run, no reminder is drafted and nothing else in the Zap counts as a task.
Step 3: Draft the Reminder With AI
Add an AI by Zapier step, which is included on paid plans, or a ChatGPT or Claude step if you already pay for API access. Map the fields from the invoice into the prompt. A prompt that works as a starting point:
Write a short payment reminder email from [your name] at [your business] to [client contact name]. Invoice [number] for [amount and currency] was due on [due date] and is now [days overdue] days overdue. Tone: friendly and direct if under 14 days overdue; firmer but still courteous if over 14 days. Mention the invoice number and amount once. Offer to resend the invoice or discuss a payment date. Do not mention late fees, legal action, or interest. Do not invent any details that are not in this prompt. Maximum 110 words. Return only the email body.
Three rules keep the draft safe:
- Give the AI only the fields it needs. Client name, invoice number, amount, due date. Do not pass bank details or unrelated notes. Our AI compliance guide covers what to check before client data goes into an AI tool.
- Forbid invented details. The line “do not invent any details” matters. Without it, a model may add a payment link or a fee that does not exist.
- Keep legal language out. Late fees and escalation threats should come from you, deliberately, not from a model.
Step 4: Hold the Draft for Your Approval
Add Zapier’s Human in the Loop step and choose Request Approval. It pauses the Zap and sends the draft to a reviewer by email or Slack. The reviewer can approve or decline, and if you enable editing, change the text first. You also set a timeout and what happens when it expires. Choose “end the run” on timeout, so an unanswered request never sends a reminder on its own. Human in the Loop is available on Professional, Team, and Enterprise plans. See Zapier’s Request Approval documentation.
Set “if declined” to stop run. A decline should mean nothing is sent.
Step 5: Send From Your Own Inbox
Add a Gmail or Outlook Send Email step. Use the client email from the invoice, a subject line that contains the invoice number, and the approved text from the approval step, not the original AI output. That way any edits you made during review are what the client receives.
Step 6: Log What Was Sent
Add a final step that appends a row to a Google Sheet or a Zapier Table: date, client, invoice number, amount, days overdue. In a month you will be able to answer two questions without guessing: how many reminders went out, and how many of those invoices were then paid.
Test Before You Turn It On
- Create a test customer with your own email address.
- Raise a small invoice to that customer with a due date in the past.
- Run the Zap and read the draft that arrives for approval.
- Decline once and confirm nothing is sent.
- Approve once and confirm the email arrives from your address with the edited text.
- Mark the test invoice paid, run it again, and confirm the filter stops the run.
What It Costs to Run
Zapier counts each successful action step as a task. A reminder that goes all the way through uses roughly five tasks: find invoice, AI draft, approval, send, log. Filters and the trigger do not count. At 30 overdue invoices a month, that is about 150 tasks, well inside the 750 on the entry Professional tier.
Common Mistakes
1. Skipping the re-check
Without the Find Invoice and Filter steps, a client who paid yesterday gets chased today.
2. Letting it send without approval “to save time”
Reading a 100-word draft takes seconds. One wrong reminder to a good client costs more than the minutes saved.
3. One tone for every client
The point of using AI here is variation. If the prompt produces the same email every time, the built-in reminder would have done the job.
4. No log
Without a log you cannot tell whether the workflow improved how fast you get paid.
FAQ
Can I do this on Zapier’s free plan?
No. The free plan is limited to two-step Zaps, and Human in the Loop requires a paid plan.
Does QuickBooks Online have an overdue trigger in Zapier?
Not by that name. Use New Invoice Due plus a Delay step, then re-check the balance before drafting.
Should the AI decide when to add late fees?
No. Fees and escalation are business and sometimes legal decisions. Keep them out of the prompt and handle them yourself.
Can I use Make or n8n instead?
Yes. The same six stages apply. Our Zapier vs Make vs n8n comparison explains which platform suits which team.
Final Recommendation
Turn on the built-in reminders today, because they are free and take ten minutes. Build this workflow when template reminders stop being enough: when you want each message to fit the client and you want to see it before it leaves. Keep the approval step permanently.
