How to collect an unpaid invoice without losing the client.
The order that works is a reminder, a call, a formal notice, then a decision about fees, pausing work, or a collections agency. Most unpaid invoices are forgotten rather than refused, so the early steps stay polite and the later ones get firm. This guide on how to collect unpaid invoices gives you the timing, the wording, the rules on late payment fees in general terms, and the way to make the next invoice pay itself at signature.
The steps, with timing.
The days below are a suggestion, not a rule. Shorten them for a small client, stretch them for a large one with a slow accounts department, and write the schedule into your payment terms.
Day 1 after due: a friendly reminder
The day after the due date, send a short email with the invoice attached and the amount and date in the first line. Assume it slipped, because an overdue invoice is usually a missed email, not a decision.
Around day 7: a second email and a call
If a week passes, send a second email and phone the person who approved the work. A call clears up most reasons an invoice stalls: a wrong PO number, a missing supplier form, or an accounts inbox nobody reads.
Around day 14: a firm email that names the next step
Two weeks in, the tone moves from helpful to clear. State the amount, the original due date, a new date a week away, and what happens after it, using the template further down this page.
Around day 30: a formal notice with a date
If a month has passed, send a final demand: a dated letter that states the debt, the deadline and what you will do next. Keep it factual and keep a copy; a court or an agency will ask to see it.
After that: pause the work, if the contract allows
If the agreement lets you suspend work for non-payment, do so and say so in writing on the same day. Pausing a live project is often the step that gets an invoice paid, so check your contract before you rely on it.
Then: small claims or an agency
For a debt that is still unpaid, the remaining routes are a small claims court, where limits and fees vary by country, or a collections agency that takes a share of what it recovers. Weigh the amount against the cost and the relationship before you choose either.
Late fees and interest, in general terms.
Whether you can charge a late fee or interest on an overdue invoice depends on two things: what your contract says, and the law in your country. In the United Kingdom, for example, a business can claim statutory interest on a late commercial payment at 8% plus the Bank of England base rate, unless the contract sets a different rate, according to GOV.UK's page on charging interest on commercial debt, checked 9 Oct 2026. In Australia, the government's guidance on writing a letter of demand, checked 9 Oct 2026, says to include a late payment interest rate only if it was specified in the contract.
The practical rule is the same in both places: put the late fee or the interest rate in the contract before the work starts, or do not count on it. A fee that appears for the first time on a final notice is easy to dispute and rarely worth the argument. LetSign does not charge or calculate late fees or interest. It takes the payment when the client signs or when a milestone falls due, which stops the problem starting.
How to stop it happening next time.
Payment at signature
The client signs the proposal and pays the first invoice in the same step, through your own Stripe account. There is no gap between yes and paid, so there is nothing to chase. See how to get paid from an AI agent's deal.
Card on file for milestones
For project work billed in stages, take a card on file at signature and charge each milestone when it is delivered. The client approved the schedule when they signed, and every payment runs through your connected Stripe account.
Subscriptions for retainers
A monthly retainer becomes a Stripe subscription at signature, so the invoice is paid on the same day each month without an invoice follow up. If a card fails, LetSign flags the account for your review.
Automatic reminders for unpaid invoices are part of the Team plan. Once a client signs, LetSign emails them the payment link every week, fortnight or month, from 1 to 12 times, and when the reminders run out the deal moves to Act now and its owner is emailed. Every action shows the exact email and runs only when you confirm. On any plan, the payment reminder email templates cover the first three steps above, and the pricing page lists what Team includes.
What to write.
Two messages for a client not paying an invoice after the friendly reminders. Replace the square brackets and send each one from your own address so the reply comes back to a person.
Subject: Invoice [number], now [days] days overdue Hi [name], Invoice [number] for [amount] was due on [date] and is still unpaid. I have attached it again. Please arrange payment by [date, one week out]. If it has not arrived by then, I will send a formal notice and pause work on [project], as our agreement allows. If something about the invoice is wrong, tell me today and I will fix it. Thanks, [your name]
FINAL NOTICE, [date] To: [client company], [address] This is a formal demand for [amount], invoice [number], due on [original due date] and now [days] days overdue. Copies of the invoice, the signed agreement and my earlier reminders are attached. Payment must reach [account details] by [date, 7 to 14 days out]. If it does not, I will refer the debt to [a collections agency or the small claims court] without further notice. [your name], [company]
Frequently asked questions
Can I stop work on an unpaid invoice?
Only if your agreement allows it. Most service contracts include a clause that lets you suspend work when an invoice is overdue by a set number of days; if yours does, say in writing that you are pausing and why. If it does not, stopping can put you in breach, so add the clause to the next contract instead.
When should I use a collections agency?
When the final notice has expired, the amount justifies the agency's share, and you have accepted that the relationship is over. Agencies usually charge a commission on what they recover, so for small sums a small claims court or a write-off is often the better choice. Hand over the signed agreement, the invoice and your reminder trail.
How do I word a final notice?
State the amount, the invoice number, the original due date and the number of days overdue. Give one clear deadline and say exactly what you will do if it passes, naming only steps you will actually take. Keep it short, factual and polite, sign and date it, and keep a copy with proof of delivery.
What if the client says they never received the invoice?
Resend it the same day, to the person who approved the work and to their accounts address, and ask for a one-line confirmation of receipt. Then restart the clock from that date with a new due date in writing. If it happens twice, ask for payment at signature on the next project.
Does an e-signed contract help me collect?
Yes, in general terms. A signed agreement that states the price, the payment terms and the due dates is the document a court or a collections agency asks for first, and an e-signature with an audit trail shows who agreed and when. A proposal signed in LetSign carries those terms and the record of the signature.
Get paid when they sign, not thirty days later.
Start free, send a proposal that takes payment at signature, and the next invoice has nothing to chase. Let your agents close the deal. You keep the client.