Straight answer: AI won't chase your invoices for you, but it will draft the emails you're too tired or too polite to write, and a firm, well-timed three-email sequence gets most small business invoices paid within a week of the final one. The tool isn't the fix. Sending the email on day three instead of day thirty is the fix, and that part is still down to you.
The invoice that sat unpaid for eleven weeks
In 2023 I did a full day of social media training for a mid-sized retailer. £4,200, thirty-day terms, invoiced the same afternoon. Nothing came. I sent a "just checking you got this" email at week two, which is the exact wrong energy to send, and got silence back. By week eight I'd written it off in my head as one of those clients you eventually stop chasing because chasing feels worse than the loss.
What moved it was three short emails I asked ChatGPT to draft for me, each one slightly firmer than the last, each one referencing a specific date and a specific number rather than a vague "when you get a chance." The third one mentioned statutory interest under the Late Payment of Commercial Debts Act. Payment landed within 48 hours of that email going out. Not because the AI was clever. Because it stopped me from writing another apologetic email and made me write a factual one instead.
That's the whole lesson of this post, really. AI is good at removing your emotional flinch from the wording. It cannot make you press send.
Why small businesses eat the cost instead of chasing it
The Federation of Small Businesses has said for years that late payment is one of the biggest single reasons small firms fail, and the UK government's own Prompt Payment Code exists because the problem is structural, not personal. Big clients pay small suppliers last because there's rarely a consequence for doing so. You're not imagining that you get treated worse than their other suppliers. You often are.
But the reason most sole traders and small agencies don't chase isn't the client's behaviour. It's that chasing feels like begging, and begging feels like admitting your business is fragile. So the invoice sits there for six weeks while you tell yourself you'll "follow up next week." I did this for years while I was rebuilding my own income after some hard years, and every unpaid invoice I let slide was money I badly needed and pretended I didn't.
The three-email sequence, with the actual timing
This is the sequence I use now for every invoice over about £300. It works because each email has a different job, and none of them apologise for existing.
- Day 0 (invoice due date): A short, warm reminder. Not an accusation. "Just flagging that invoice #1042 for £X was due today, let me know if you need anything from me to process it."
- Day 7: Firmer, references the terms explicitly. "This invoice is now seven days overdue against our agreed 30-day terms. Can you confirm a payment date this week?"
- Day 14: States the consequence in plain numbers. Under UK law you're entitled to charge statutory interest at 8% plus the Bank of England base rate on unpaid commercial invoices, plus a fixed compensation fee (£40 to £100 depending on the invoice size). You don't have to charge it. Just mentioning it, correctly and without threat in your voice, changes the tone of the reply you get back.
Three emails. Fourteen days. If nothing's moved by day 14, that's when you pick up the phone, because email at that point starts looking like something a client can keep ignoring.
The exact prompt I use
I give ChatGPT or Claude the invoice number, amount, due date, and how many days overdue, then ask for this specifically:
- "Write a short payment reminder email for invoice #[X], £[amount], due [date], now [Y] days overdue. Keep it under 80 words, no apology, no exclamation marks, state the fact and ask one direct question."
That last instruction, no apology, matters more than anything else in the prompt. Most people's natural draft opens with "Sorry to chase you on this" and that one sentence undoes the whole email. AI will happily write the apologetic version too if you let it, because that's the tone most invoice-chasing emails on the internet use. You have to explicitly ask for the version without it.
What AI is good at here, and what it isn't
It's good at three things: removing the emotional wobble from your wording, calculating the exact interest owed so you're not guessing, and drafting a version that sounds firmer than you feel. I'm not a technical person and I use it every single day for exactly this kind of unglamorous admin, not for anything clever.
It's bad at, and this is the bit most posts on this topic skip past, making you send it. I've sat on AI-drafted chase emails for a week because sending them still felt uncomfortable. The draft existing in a document does nothing. Some founders will read this and quietly admit they've got three or four unsent drafts sitting in a folder right now. If your late payment problem is really an avoidance problem, no tool fixes that. You still have to click send on a Tuesday morning when you'd rather not.
Put the maths in front of the client, not just the words
One thing that's changed how quickly I get paid is showing the client the actual number, not just describing it. If a client can see, in black and white, exactly what 8% plus base rate comes to on their specific invoice over their specific number of overdue days, it lands differently than a sentence saying "interest may apply." This is the same principle behind interactive calculators used on websites to convert visitors, people trust and act on numbers they can see calculated in front of them far more than numbers described to them in a sentence. I now keep a simple spreadsheet formula for this rather than a calculator page, but the psychology is identical: specificity beats vagueness every time.
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Set the terms up front so you chase less
The chase sequence matters less if your payment terms are tight from the start. A few things that cut my late payments by roughly half over eighteen months:
- 14-day terms instead of 30 for anything under £2,000. Most clients don't push back, they just assumed 30 was standard because everyone else uses it.
- 50% deposit on new client work over £1,000, always. Existing clients with a track record can stay on invoice-after terms.
- A payment link on the invoice itself, not a bank transfer request buried in an email three messages later. Every extra step you add between "I owe this" and "I've paid it" loses you days.
- A free, simple invoice template rather than a bespoke one you have to rebuild each time. There's a decent one buried in this list of underused websites worth knowing about, and consistency in your invoice format alone makes clients treat it as a formal document rather than a casual reminder.
What changed for me after I stopped writing the apology emails
My average time to payment went from around 41 days to 19 days once I ran this sequence for six months, tracked against my own invoicing software records. That's not a huge scientific sample, it's one small business, but it's a real number from my own books, not a stat I've borrowed from somewhere else. The eleven-week client from earlier in this post is now one of my better payers, oddly enough, because the firm email reset the relationship rather than damaging it. Clients respect a supplier who knows their own terms. They don't respect one who keeps quietly hoping.
If you're building any part of your income back up right now, whether that's client work, content, or a mix, the boring admin like this is the part that protects the revenue you've already earned, not the part that generates new revenue. It's less exciting to write about than growth tactics. It matters more to your bank balance most months.
Frequently asked questions
Can AI write a legal-sounding demand letter for unpaid invoices?
It can draft the wording, but don't call it a legal letter unless a solicitor has reviewed it. What AI is useful for is drafting a firm, factual "Letter Before Action" style email that states the amount owed, the overdue period, and the statutory interest you're entitled to under UK law, which is often enough to trigger payment before you need any actual legal step.
How much interest can I legally charge on a late invoice in the UK?
Under the Late Payment of Commercial Debts Act, small businesses can charge statutory interest of 8% plus the Bank of England base rate on overdue commercial invoices, plus a fixed compensation fee of £40 to £100 depending on invoice size. You're not obliged to charge it, but mentioning it accurately in a chase email noticeably changes how quickly clients respond.
What's the best AI tool for writing chase emails, ChatGPT or something else?
Any general AI writing tool works fine for this, ChatGPT, Claude, or Gemini all produce a usable draft in seconds. The tool matters far less than the prompt. Ask specifically for a short, non-apologetic, fact-based email with one direct question, or you'll get the same soft, over-polite draft most people naturally write.
Should I stop working with a client who is consistently late paying?
If a client is late more than twice in a row despite clear terms and a proper chase sequence, that's a pattern, not an accident. Move them to upfront payment or a deposit model before you take on more work for them. Chronic late payers rarely change on their own, and continuing to extend the same terms just teaches them that late payment has no real consequence with you.
Related: looking for an AI consultant for small business? Here is how I can help.
Related reading: The AI Subscription Stack: What I Pay For (and What I Cancelled) in 2026 and I Got AI to Chase My Late Invoices. Here's What Happened.
