Payment Reminder Email Templates: How to Follow Up on an Unpaid Invoice

A good payment reminder names the invoice number, the amount and the due date, gives the client one clear way to pay, and gets a little firmer at each step while staying polite. Send it early, keep it short, and attach the invoice again so nobody has to go looking for it.

Below are seven templates you can copy, one for each stage of an unpaid invoice, plus subject lines and a way to tell whether the problem is delivery or approval. Replace everything in {braces} before you send.

What every payment reminder needs

The reminder is only useful if the person reading it can act on it in under a minute. That means the email has to carry everything the finance team would otherwise have to ask you for.

• The invoice number. Accounts payable teams search by number, not by project name.
• The amount and currency. State it in full, even if it is in the attached invoice.
• The original due date. Say it plainly, with no accusation attached.
• One way to pay. A payment link, or the bank details written out. Not three options.
• The invoice attached again. Never assume the first email is still findable.
• Who to contact if there is a problem. A wrong purchase order number or a missing approval is far easier to fix when the client knows to tell you.

A reminder schedule you can adapt

There is no universal rule for timing. Treat this as a sensible default and adjust it to your payment terms and to how well you know the client.

1. 1A few days before the due date: a friendly heads-up.
2. 2On the due date: a short note with the payment link.
3. 3About a week overdue: a polite check that nothing has gone wrong.
4. 4About two weeks overdue: a clearer request for a payment date.
5. 5About 30 days overdue: a firm message, ideally with a call offered.
6. 6Final notice: the last written step before you change how you work with the client.

The same logic applies to any chase. The gap between messages and the number of messages are covered in how many follow-up emails to send.

Template 1: upcoming payment reminder (a few days before)

This one is a courtesy, not a chase. It is also the easiest email to write, and it catches the invoices that would otherwise slip past the due date unnoticed.

Template 2: on the due date

Template 3: about a week overdue

Assume it was missed, not refused. A late invoice is often simply forgotten, and a blame-free tone keeps the relationship intact.

Template 4: about two weeks overdue

Template 5: about 30 days overdue

By now the tone should be firm and factual. Stay calm, offer a call, and ask for a specific date. Do not add adjectives.

Template 6: final notice

Template 7: the client says it is in approval

This is a very common reply to an overdue reminder. Do not just wait. Use it to find out who is actually responsible and what they need.

Subject lines that get payment reminders opened

Put the invoice number in the subject line every time. It makes the email searchable for the client and tells them exactly what it is before they open it.

• Invoice {invoice number} for {amount} is due on {due date}
• Reminder: invoice {invoice number} is due this week
• Invoice {invoice number} is due today
• Following up on invoice {invoice number}
• Quick check on invoice {invoice number}
• Invoice {invoice number}: did this reach the right person?
• Invoice {invoice number} is now overdue
• Action needed: overdue invoice {invoice number}
• Final notice: invoice {invoice number}

Avoid all capitals, exclamation marks and dramatic wording. They look like spam and can push a legitimate invoice into the junk folder. If deliverability is a worry, why emails land in spam covers the usual causes.

Not opened versus opened and not paid

If you can see what happened to your earlier emails, it changes what you should do next. The two cases need opposite responses.

If the earlier reminders were never opened, the problem is probably delivery or the wrong contact, not a reluctant client. Do not make the tone firmer. Check the address for typos, check whether the person has left the company, ask whether your emails reached their spam folder, and resend to a second contact if you have one. A short phone call often resolves it in a minute.

If they opened it several times and still have not paid, the invoice is often stuck in approval, waiting for someone to sign off or for a purchase order. Use Template 7: ask who handles accounts payable and whether anything is needed from you.

For more on reading engagement without over-reading it, see an open is not intent.

Late fees and final notices

Only charge a late fee if your contract or terms say so, and only at the rate they state. Adding a fee after the fact, with no agreement behind it, turns a payment problem into a dispute.

Never threaten something you will not do. If your final notice says you will pause work, you must be prepared to pause work. An empty threat costs you credibility with every later message.

Rules on late fees, interest and debt collection differ between countries and between states, so check the rules where you and your client are based before you rely on any of them. If a large invoice is in serious trouble, get proper advice rather than escalating by email.

There is also a point at which more reminders stop helping. When to stop following up is worth reading before you send a seventh message, and the follow-up after no response guide has more sample wording for clients who have gone silent.

Where MailSenseAI fits

MailSenseAI is a free Chrome extension that shows, inside Gmail, whether each email was opened, clicked or replied to, so you can see whether a reminder was never opened or opened and left unpaid. It never adds a footer to your emails on any plan, which matters when the message is an invoice and a third-party badge would look unprofessional. Tracking is free and unlimited, and there are AI follow-up drafts if you want a starting point. See how it handles footers for the detail.