Guides · Updated 2026-10-20

AI Invoice Reminder Templates: Polite to Firm (Email, WhatsApp and SMS)

Chasing unpaid invoices is one of the least enjoyable jobs in a small business, and it's usually the owner who ends up doing it. A clear, regular sequence of reminders takes most of the awkwardness out of it. This guide gives you a polite-to-firm reminder ladder, ready-to-copy email, WhatsApp and SMS templates for every stage, AI prompts to adapt them to your industry and client, and the tone and legal checks to make before anything firm goes out. The prompts work in the free versions of ChatGPT, Google Gemini and Microsoft Copilot.

Short answer: send a friendly reminder a few days before the due date, a short note on the due date, then reminders at 3, 7, 14 and 30 days late, getting a little firmer each time, and finish with a dated final notice. Every message should state the invoice number, amount, due date and how to pay, in one or two short paragraphs. Only mention late fees or interest if your contract or the law in your country allows them, and never threaten a step you don't intend to take.

Replace anything in [brackets] with your details. When you use AI to adapt a template, you don't need to paste in the client's full name, address or bank details: write [client] and [amount] and fill them in yourself before you send.

The reminder ladder at a glance

This is a starting point, not a rule. If your payment terms are 7 days, compress the ladder; if you invoice large companies with 30- or 60-day terms, you may only need stages 1, 2, 3, 5 and 7. Whatever you choose, use the same sequence for every client, so no one feels singled out.

Before you chase: make invoices easy to pay

Many "late" invoices are invoices that were hard to pay or went to the wrong person. A few minutes here saves several reminders later.

• Put a date, not just "30 days", on the invoice: "Due 14 November 2026" is harder to misread than "Net 30".
• Add a payment link or full payment details on the invoice itself, plus the invoice number as the payment reference.
• Send it to the person who pays, and ask larger clients whether they need a purchase order (PO) number or a supplier form first.
• Write your late-payment terms down before you start the work, in your quote, contract or terms, if you plan to charge fees or interest.
• Keep a simple log of every invoice: number, client, amount, due date, and the date of each reminder. A spreadsheet is enough.

Email templates for each stage (copy-paste)

Stage 1: friendly reminder before the due date

Subject: Invoice [number] due on [date]

Hi [first name],

A quick heads-up that invoice [number] for [amount] is due on [date]. I've attached it again for easy reference, and you can pay here: [payment link or bank details].

Thanks again for your business, and let me know if you need anything from me.

[Your name]
[Business name] · [phone]

Stage 2: due date

Subject: Invoice [number] for [amount] is due today

Hi [first name],

Just a reminder that invoice [number] for [amount] is due today. You can pay by [payment method] using [link or details], with [invoice number] as the reference.

If it's already on its way, thank you, and please ignore this message.

[Your name]

Stage 3: 3 days late

Subject: Quick reminder: invoice [number] (due [date])

Hi [first name],

I couldn't see payment for invoice [number] ([amount], due [date]) yet, so I'm checking it didn't get lost in your inbox. I've attached a copy.

Could you let me know when we can expect payment? Here's the link again: [payment link].

Thanks,
[Your name]

Stage 4: 7 days late

Subject: Invoice [number] is now 7 days overdue

Hi [first name],

Invoice [number] for [amount] was due on [date] and is now a week overdue. If there's a problem with the invoice or the work, please tell me and I'll sort it out quickly.

Otherwise, please arrange payment by [date, about 3–5 working days away] or reply with a date that works for you.

[Your name] · [phone]

Stage 5: 14 days late

Subject: Overdue: invoice [number], 14 days past due

Hi [first name],

Invoice [number] for [amount] is now 14 days past its due date of [date], and I haven't had a reply to my earlier reminders. I've copied [accounts contact] in case this needs to go to your accounts team.

Please pay by [date]. If paying in one go is difficult right now, I'm happy to agree a short payment plan; just reply and we'll work it out.

[Only if your terms or the law allow it: As set out in our terms, late payments may incur [fee/interest]. I'd rather not apply it, so please get in touch.]

[Your name]

Stage 6: 30 days late

Subject: Invoice [number]: 30 days overdue, action needed

Dear [first name],

Invoice [number] for [amount], due on [date], is now 30 days overdue. I've sent reminders on [dates] and haven't yet received payment or a payment date.

Please pay the outstanding [amount] by [date, 7 days away]. [If your terms allow: Under our terms, we'll pause further work on [project/account] until the account is up to date.] If you'd like to discuss a payment plan, please call me on [phone] before then.

Regards,
[Your name], [Business name]

Stage 7: final notice

Subject: Final notice: invoice [number], payment due by [date]

Dear [first name],

This is a final notice for invoice [number] for [amount], which was due on [original due date]. Previous reminders were sent on [dates].

If we don't receive payment or hear from you by [deadline], we will [the next step you have decided on and are entitled to take, e.g. pass the account to a collection agency / start a small-claims process / apply late-payment interest as set out in our terms].

We'd much prefer to settle this directly. You can pay at [link or details], or call me on [phone] to agree a plan.

Regards,
[Your name], [Business name]

WhatsApp and SMS versions

Short messages work well for sole traders, trades and service businesses whose clients already message them. Keep them shorter than the emails, include the invoice number and amount, and point to the email or link for the details. A standard SMS holds 160 characters (fewer if it contains emoji or some accented letters); longer texts are split into several parts and may cost more, so the SMS versions below are kept short.

WhatsApp (friendlier, can be a little longer):

• Before due: Hi [first name], friendly reminder that invoice [number] for [amount] is due on [date]. Pay here: [link]. Thanks! [Your name], [Business]
• Due date: Hi [first name], invoice [number] ([amount]) is due today. Here's the payment link: [link]. Please ignore this if you've already paid. Thanks!
• 3 days late: Hi [first name], just checking you got invoice [number] for [amount], due [date]. Could you let me know when it'll be paid? Link: [link]
• 7 days late: Hi [first name], invoice [number] for [amount] is now a week overdue. Is anything holding it up? Happy to help if there's a problem. [link]
• 14 days late: Hi [first name], invoice [number] ([amount]) is now 2 weeks overdue. Please pay by [date] or let me know if a payment plan would help. I've emailed the details.
• 30 days late / final: Hi [first name], I've emailed a final notice for invoice [number] ([amount]). Please pay or call me by [date] so we can settle it directly. [Your name]

SMS (kept short):

• Before due: [Business]: invoice [number] for [amount] is due [date]. Pay: [short link]. Thank you!
• Due date: [Business]: invoice [number] ([amount]) is due today. Pay: [short link]
• Late: [Business]: invoice [number] ([amount]) is overdue since [date]. Please pay at [short link] or reply with a date.
• Final: [Business]: final notice for invoice [number] ([amount]) sent by email. Please pay or call [phone] by [date].

Only message clients on WhatsApp or by SMS if they gave you that number and you already talk to them that way. Keep reminders to the invoice: don't add promotions or offers to a payment reminder.

AI prompts to personalise your reminders

Templates get you most of the way. These prompts adapt them to your client, your industry and your own voice. Paste in a template from above and replace the [brackets].

1. Rewrite this invoice reminder so it sounds like me: a [friendly/plain/formal] [business type] owner in [country]. Keep the invoice number, amount, due date and payment link exactly as they are, don't add anything I haven't said, and keep it under 90 words. Reminder: [paste template]

2. Turn these 7 invoice reminder emails into a matching set of WhatsApp messages under 50 words each and SMS messages under 160 characters each. Keep every [placeholder] as it is. [paste templates]

3. This client usually pays on time and is now [X] days late. Write a short, warm reminder that assumes it was an oversight, asks for a payment date, and doesn't mention fees. Under 70 words.

4. This client has ignored [number] reminders. Write a firm but polite email that lists the dates of the earlier reminders ([dates]), asks for payment by [date], offers a payment plan, and contains no threats. Under 120 words.

5. A client replied that they're short of cash this month. Draft a reply that thanks them for telling me, proposes [number] payments of [amount] on [dates], and asks them to confirm in writing. Under 100 words.

6. Read this reminder and flag anything that sounds rude, passive-aggressive, threatening or legally risky, or that promises something I may not be able to do. List the issues; don't rewrite it. [paste draft]

Ready-made prompts by industry:

7. Trades and home services: Write a payment reminder for a [job type] completed at a client's home on [date], invoice [number] for [amount]. Friendly, mention the job in one line so they recognise it, no mention of their address. Include an option to pay by [method]. Under 80 words.

8. Agencies and freelancers: Write a reminder for invoice [number] for [project/milestone], due [date]. Professional and friendly, mention that [next milestone/deliverable] is scheduled once the account is up to date [only if your contract says so]. Under 90 words.

9. Coaches and consultants: Write a discreet reminder for [package/session block] invoice [number]. Don't mention anything we discussed in sessions. Warm, short, with the payment link. Under 70 words.

10. Accountants and bookkeepers: Write a reminder for our [month] fee invoice [number] that's polite, mentions no client figures or filings, and reminds them that [the service] continues on schedule. Under 70 words.

11. Restaurants, cafés and caterers: Write a reminder to a corporate client for the [event/catering order] on [date], invoice [number], addressed to their accounts team. Ask whether they need a PO number or supplier form to process it. Under 80 words.

12. Salons, fitness studios and trainers: Write a friendly message about an unpaid [package/membership/session] balance of [amount]. Keep it light, don't mention anything about their body, health or appointments in detail, and offer an easy way to pay. Under 50 words, suitable for WhatsApp.

13. Clinics and dental practices (admin only): Write a neutral account reminder for an outstanding balance of [amount] on account [reference]. Don't mention any treatment, visit or health details. Polite, short, with payment options. Under 60 words.

AI tools sometimes change numbers or add details that aren't true. Before you send, check the invoice number, amount, dates and payment details against your own records.

Tone tips that get invoices paid

• Start by assuming good faith. Most late payments are oversights, cash-flow problems or invoices sent to the wrong person. The first reminders should make paying easy, not make the client feel accused.
• Be specific every time. Invoice number, amount, original due date and a payment link in every message, so the client never has to search for anything.
• Ask a question. "When can we expect payment?" gets more replies than "Please pay." A reply gives you a date to hold them to.
• Get firmer in steps, not jumps. Move from "friendly reminder" to "overdue" to "final notice". Don't skip straight from polite to threatening.
• Pick up the phone at around 7 days late. A short, friendly call often finds the real problem (a missing PO number, a query about the work) faster than another email.
• Offer a way out. A payment plan is often better than a long dispute. Confirm any plan in writing.
• Stay calm in writing. No capitals, no exclamation marks in later stages, and nothing you wouldn't want read aloud in a dispute.

Legal caution: late fees, interest and what not to say

This section is general information, not legal advice. Rules on late payment differ between countries, and sometimes between states or provinces, and they're often different for business clients and consumers.

• Only charge what you're entitled to. Add late fees or interest only if your contract, terms or invoice set them out before the work, or if the law in your country gives you that right. Check your local rules before you mention any figure. For example, in the UK businesses can claim interest and debt-recovery costs on late business-to-business payments (GOV.UK guidance on late commercial payments), and the EU has a Late Payment Directive for business and public-sector payments. Rules for consumers are usually stricter.
• Don't let AI invent the rules. Don't ask an AI tool what late fee you're allowed to charge and copy the answer. It may describe another country's law or make it up. Check with an official government source, your accountant or an attorney.
• Never threaten a step you don't intend or aren't entitled to take, such as legal action, a collection agency or a credit report. If the final notice names a next step, be ready to take it on that date.
• Keep it between you and the client. Don't contact their family, employer or other customers about the debt, and never mention it publicly or on social media.
• Keep records of the invoice, your terms, every reminder and every reply. If the debt ends up with a collection agency or a small-claims court, those records are what count.
• Get advice before the last step. Before you go to court or hand the account to a collector, speak to an attorney, a collection agency or your local small-business support service about the process in your country.

Frequently asked questions

How do I politely remind a client that an invoice is overdue?

Keep it short and specific: give the invoice number, amount and original due date, attach the invoice again, include a payment link, and ask when you can expect payment. Assume it was an oversight in the first reminder. The stage 3 template above is a good starting point.

When should I send the first invoice reminder?

A friendly reminder 3–5 days before the due date works well, followed by a short note on the due date itself. Neither is pushy: they make it easy for the client to pay on time, and they catch invoices that went to the wrong person early.

How many payment reminders should I send before a final notice?

A common sequence is a reminder before the due date, one on the due date, and reminders at 3, 7, 14 and 30 days late, followed by a final notice with a set deadline. Shorten it if your payment terms are short. Add a phone call at around 7 days late.

Can I charge a late fee on an overdue invoice?

Only if your contract, terms or invoice set out the fee or interest before the work was done, or if the law in your country gives you that right. Rules differ by country, and often between business and consumer clients, so check an official source or ask your accountant before you mention any figure.

Is it OK to send invoice reminders by WhatsApp or SMS?

Yes, if the client gave you that number and you already communicate that way. Keep the message short, include the invoice number, amount and a payment link, leave out promotions, and send the formal details, especially for later reminders and final notices, by email as well.

Can AI write invoice reminder emails for me?

Yes. ChatGPT, Gemini and Copilot can adapt a template to your tone, your industry and the situation in seconds. Use placeholders instead of the client's personal details, and check the invoice number, amount, dates and any mention of fees before you send, because AI tools can change numbers or add claims that aren't true.

More help with the admin side of a small business: read our guides on writing quotes with AI and how to use ChatGPT for small business, or the AI guides for trades and home services, agencies and freelancers, coaches and consultants and accountants and bookkeepers.

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