I Got AI to Chase My Late Invoices. Here's What Happened

The short version: AI can write your invoice-chasing emails, escalate the tone at the right moment, and save you the two hours a month you spend agonising over how to word "please pay me." It cannot fix the reason the invoice is late in the first place, and if your payment terms are vague, AI will just help you send polite nonsense faster.

The invoice that started this whole experiment

Last spring a client, a mid-sized events company I'd done a marketing audit for, owed me £3,800. The invoice went out on a Friday. Terms said 30 days. On day 63 I still hadn't been paid, and I still hadn't chased it, because chasing money makes me feel like I'm begging, and I hate that feeling more than I hate not being paid.

That's the bit nobody says out loud. Most of us don't have a system for late invoices because we don't want to think about the fact that we need one. I had sent one limp email on day 35 that said "just checking you got this, no rush," which is the exact opposite of what you should say when someone owes you nearly four grand.

So I built a proper sequence, using ChatGPT to draft it and my own invoicing history to test it. Three months and eleven late invoices later, here's what works, what doesn't, and the uncomfortable truth about why the invoices were late at all.

The three-email sequence I now use for every late invoice

This isn't complicated. It's three emails, sent at three fixed points, each one written in a different tone. I built the templates once with AI, saved them, and now I just fill in the name and amount. It takes me about four minutes per client instead of the twenty minutes I used to spend drafting from scratch and softening every sentence three times.

• Day 1 after due date: Friendly, assumes it's an oversight. "Hi Sarah, just flagging that invoice #204 for £3,800 was due yesterday, I imagine it's slipped through, could you let me know when it's likely to be paid?"
• Day 14 after due date: Neutral and factual. States the amount, the original due date, references your payment terms, asks for a specific date.
• Day 30 after due date: Direct. States that under the Late Payment of Commercial Debts (Interest) Act, you're entitled to add statutory interest plus a fixed compensation fee, and asks for payment within seven days before you take that step.

That last point matters and most freelancers in the UK don't know it exists. If you're owed under £1,000, you can add £40 compensation on top of statutory interest at 8% plus the Bank of England base rate. On a £3,800 invoice that's over £150 in interest and compensation once you're 60 to 90 days late. You don't have to ever charge it, but mentioning that you're entitled to gets more invoices paid in a week than any polite chasing email ever will. There's a plain-English explanation of the whole thing on the gov.uk late payment page if you want the exact figures for your own invoice.

The exact prompt I use to draft each one

I'm not technical, and I've written before about how I use AI every day without any of the fancy setup. This is the same principle. You don't need automation software or a CRM plug-in for this. You need one prompt, typed into ChatGPT or Claude, that you reuse and adjust.

Here's the actual prompt, word for word, that I use for the day-30 email:

"Write a short, calm, professional email chasing an unpaid invoice that is now 30 days overdue. The client's name is [name]. The invoice number is [number] and the amount is [amount], originally due on [date]. Mention that under UK late payment legislation I'm entitled to add statutory interest and a fixed compensation fee, but that I'd rather resolve this without needing to. Ask for payment within 7 days. Keep it under 120 words, no exclamation marks, no apologising for chasing."

That last instruction, no apologising, is the one that changes everything. AI defaults to soft, apologetic language because most of the training data for "how to write a polite email" comes from people who are, like most of us, uncomfortable asking for money. You have to tell it explicitly not to soften.

The number that made me take this seriously

Small businesses in the UK are collectively owed around £22 billion in late payments at any given time, according to figures reported by the Federation of Small Businesses, and the average small business waits closer to 50 days beyond agreed terms to get paid, not 30. If you invoice £4,000 a month and half of it comes in three weeks late every single time, that's not a cash flow blip, that's an interest-free loan you're giving your clients without meaning to.

I did the maths on my own year. Across 34 invoices, the average delay past terms was 19 days. That's not one bad client, that's a pattern, and patterns are the thing AI is good at spotting once you feed it your own invoice log. I pasted a year of invoice dates and payment dates into a spreadsheet, asked ChatGPT to find the slowest-paying clients, and two names came up in the bottom five every time. One of them was the £3,800 events company.

The uncomfortable bit: AI didn't fix my invoices, my terms were the problem

Here's what I don't see written anywhere else on this topic. The chasing sequence works, but it's treating a symptom. When I looked at why that events client was 63 days late, the invoice itself said "payment due within 30 days" with no date, no late fee clause, and no deposit had been taken upfront. It was a project worth £3,800 and I'd let all of it ride on their goodwill and my own reluctance to look pushy.

AI cannot fix that. It will happily write you a beautifully worded chasing email forever, on a loop, while you keep issuing invoices with soft terms that invite exactly this behaviour. The fix isn't a better email, it's a 50% deposit before work starts, a fixed due date printed on the invoice itself (not "30 days," an actual calendar date), and a one-line late fee clause in your contract that you mention before you ever need to enforce it.

Since I changed my invoice template to include a specific date and a stated late fee, my average delay dropped from 19 days to 6. The chasing emails still exist, I still need them occasionally, but I send about a third as many as I did a year ago. The email sequence is a good bandage. The invoice terms are the actual cure.

Setting this up without buying new software

You don't need a dedicated invoicing platform to run this. If you already use Xero, QuickBooks, or FreeAgent, they all have basic automatic reminder features built in, though most people never turn them on. What I added on top is the AI-drafted escalation sequence for the invoices that slip past even those automatic reminders, because automated system emails get ignored the way bank overdraft warnings get ignored, they don't feel personal.

Step by step, this is what I do now:

• Invoice goes out with a specific due date and a stated late fee clause, not "30 days net."
• Accounting software sends its automatic reminder on the due date.
• If unpaid after 14 days, I run the AI prompt above, personalise it with the client's name and history, and send it myself, from my own email, not the accounting software.
• If unpaid after 30 days, second AI email mentioning statutory interest.
• If unpaid after 45 days, phone call. Not email. This is the one step AI can't do and shouldn't try to. A two-minute phone call gets more invoices paid than any email at this stage, because it's much harder to ignore a person's voice than a message.

That combination of automatic reminders, AI-drafted personal follow-ups, and one phone call as the last resort has moved every single overdue invoice I've had in the last four months, some of them within 48 hours of the second email going out.

Where this connects to the rest of your business

Chasing invoices better is a cash flow fix, not a growth strategy, and it's worth being honest about that. It won't bring in new clients. But it does something quieter and just as important, it stops you resenting the clients you already have. I've watched myself go cold on a client relationship simply because they were consistently the slowest payer on my books, even though the work itself was fine. Fixing the payment terms fixed the relationship, not just the bank balance.

If your invoicing, contracts, and follow-up sequences feel like something you keep meaning to sort out and never do, that's exactly the kind of unglamorous operational tangle an AI implementation coach can help you build once, instead of patching it every few months like I did for years.

And if you're the sort of person who collects useful tools the way I do, I've got a running list in 50 Websites You Didn't Know Existed that includes a couple of free invoice and contract generators worth bookmarking alongside whatever accounting software you already use.

It felt a bit like the shift I wrote about in The Month My Website Started Paying Me Again, except this time it wasn't Google sending traffic back, it was a client finally sending the £3,800 they'd owed me for two months. Same relief, different source.

Frequently asked questions

Can AI chase invoices for me automatically, without me sending anything?

Not reliably yet, not without connecting it to your email and accounting software in a way most small businesses don't have set up. What works right now is using AI to draft the emails at each stage while you still hit send yourself, so the message still looks and sounds like it came from a person, not a bot.

What's the best tone for a late payment email?

Calm, specific, and free of apology. State the invoice number, the amount, and the original due date in the first two lines. Avoid exclamation marks and phrases like "just a gentle reminder," which soften the message so much it reads as optional.

Can I charge interest on a late invoice in the UK?

Yes, for business-to-business invoices. Under the Late Payment of Commercial Debts (Interest) Act, you can add statutory interest at 8% plus the Bank of England base rate, plus a fixed compensation fee of £40 to £100 depending on the invoice size, once payment is overdue. You don't have to enforce it, but mentioning it in a day-30 email tends to get invoices paid faster.

Why do my invoices keep coming in late even when I chase them well?

Usually the terms, not the chasing. A vague due date like "30 days" instead of an actual calendar date, no deposit taken upfront, and no stated late fee all signal to clients, often unintentionally, that your payment terms are flexible. Fixing the invoice itself tends to reduce late payments far more than any follow-up email sequence.

Want this done for you? See how to get your business cited by ChatGPT and Perplexity.

Related reading: The AI Subscription Stack: What I Pay For (and What I Cancelled) in 2026 and How I Use AI to Chase Late-Paying Clients Without Sounding Like a Debt Collector.

I go much deeper on this in the AI marketing guide.