Set a short sequence (a note just before the due date, reminders at about 3, 10 and 21 days overdue, then a phone call) and let AI personalise each email from the invoice and client history: their name, the actual work, what's been said. Keep each under 80 words with one request, and stop the sequence when the client replies.
That last rule does more for "sounding human" than any wording. Nothing gives away an automated chaser faster than a reminder that arrives the day after the client wrote back to say they'd paid, or that the invoice went to the wrong person. A human who chases money reads the replies. So must the automation.
Why automated reminders read like a machine
Here is a typical default reminder, the kind many accounting systems send out of the box (illustrative):
Dear Valued Customer, This is a reminder that invoice INV-4471 for $385.00 is now OVERDUE. Please arrange payment at your earliest convenience. If you have already paid, please disregard this message. Kind regards, Accounts Department
Five things mark it out as automated: no name, capital letters, no mention of what the money was for, a sender that isn't a person, and "please disregard this message", which tells the client nobody checked. Here's the same reminder written the way a person would write it:
Hi [first name], a quick one: our invoice for September's bookkeeping and the payroll run (INV-4471, $385) was due last Friday and I can't see it on our side yet. There's a pay link on the invoice if that's easiest. If anything on it looks wrong, just reply and I'll sort it. Thanks, [your name]
Same information, same length, very different response. It names the work, gives a date rather than a label, offers a way out if there's a problem, and comes from someone. AI's job is to produce the second version for every overdue invoice, using real details, without anyone typing them.
A reminder sequence that escalates without turning cold
The running example is an illustrative eight-person bookkeeping firm with about 160 small-business clients on monthly fees between $180 and $900. It bills around $41,000 a month and had drifted into chasing by hand, whenever someone had a spare hour. Its new sequence:
| When | Channel | Tone | What it says |
|---|---|---|---|
| 3 days before due | Helpful | A heads-up with the pay link. Only for clients who have paid late before. | |
| 3 days overdue | Light, assumes an oversight | The work, the amount, the pay link, "reply if anything's wrong" | |
| 10 days overdue | Direct, still friendly | Asks for a payment date; mentions it's the second note | |
| 21 days overdue | Email, then phone within 2 days | Firm | States the amount and days overdue; says the account manager will call |
| 30+ days overdue | Phone, then final notice letter | Formal, factual | What happens next and by when; any pause in service under the engagement terms |
Two design choices matter. The pre-due note goes only to clients with a history of paying late, because sending it to everyone makes good payers feel watched. And a person takes over at day 21. By then the email has done what it can; a short call finds out whether the problem is forgetfulness, cash flow or a dispute, and each needs a different response.
What the AI needs to know to sound like you
Personalisation comes from data, not from asking the AI to "be friendly". For each overdue invoice, the automation should pass:
- The contact's first name and the account manager's name
- Invoice number, amount, due date and days overdue
- What the invoice was for, in plain words (from the invoice lines)
- How this client usually pays: always on time, usually a week late, or erratically
- Earlier reminders already sent for this invoice, and any reply
- Other overdue invoices on the account
- Two or three real emails the account manager has written, as a style sample
The style sample is the difference between "friendly AI" and "sounds like you". It shows the AI how he opens, how long his sentences run and how he signs off. For more on capturing a house style in prompts, see writing AI prompts that sound like your business.
The prompt, and what it produces for three kinds of payer
Write a payment reminder email from {account_manager} to
{contact_first_name}.
Facts (use exactly, never change amounts or dates):
- Invoice {number}, {amount}, for {work_description},
due {due_date}, now {days_overdue} days overdue.
- This is reminder {n} of 4. Previous reminders: {history}.
- Other overdue invoices: {others}.
- Payment pattern: {pattern}.
Style: match the sample emails below. Under 80 words. One
request only. Mention the work in plain words. Offer a reply
route if something's wrong with the invoice.
Never: capitals for emphasis, "valued customer", "as per",
"kindly", "disregard", threats, legal language, interest,
or anything not in the facts.
Tone for reminder {n}: {tone_from_table}.
Style samples: {samples}Illustrative outputs for three different clients at the 10-day stage:
A good payer who has slipped (paid on time for two years):
Hi [first name], not like you to be late, so I'm guessing August's invoice (INV-4402, $540, month-end accounts and the quarterly return) slipped through. Could you let me know when it's likely to go? Thanks, [your name]
A habitual late payer (usually pays 2 to 3 weeks late):
Hi [first name], following up on INV-4415 ($260, September bookkeeping), now 10 days past due. Could you give me a date for payment this week? If it's easier, the pay link on the invoice takes card payments. Thanks, [your name]
A client who has gone quiet (no reply to the first reminder, two invoices overdue):
Hi [first name], I haven't heard back about the two open invoices, INV-4388 ($720) and INV-4431 ($720), for August and September. If something's changed, or there's a question about the work, I'd rather hear it now so we can sort it out. Could you reply or give me a call this week? [your name]
What you'd fix before trusting this at scale: in testing, the first version of the prompt turned "quarterly return" into "quarterly tax return", which was wrong for that client, so the prompt now says "use the work description exactly as given". And for the quiet client, the AI initially wrote "we value your business", which is exactly the phrase that makes a reminder sound generated. It's now on the banned list.
Tone rules to put in every reminder prompt
- Name the work. "September's bookkeeping" is harder to ignore than "invoice 4415".
- One ask per email. Pay, or give a date, or reply. Not all three.
- Offer a route out. "If anything looks wrong, reply" surfaces disputes early, which is when they're cheapest to fix.
- Use dates, not labels. "Due last Friday" rather than "OVERDUE".
- Escalate by being specific, not by being cold. The firm stage states the amount, the days and what happens next. It doesn't need sarcasm or capitals.
- No invented facts. Amounts, dates and descriptions come from the data, word for word.
- No legal threats in automated emails. Anything about interest, collection or pausing work goes in a letter a person has approved.
Where to run it: built-in reminders or an automation
Your accounting system's reminders are the simplest start. Xero allows up to five reminders on a single schedule for the whole organisation, each a set number of days before or after the due date, with defaults at 7, 14 and 21 days overdue. QuickBooks Online allows up to three automatic reminders, each up to 90 days either side of the due date, set in Account and settings under Sales. Both let you edit the wording and insert fields such as the contact name and amount. QuickBooks Online's Payments AI can also suggest a reminder schedule and draft invoice-specific reminder emails, which you review before approving.
The limits: built-in reminders use the same template for everyone, can't read the client's reply, and can't vary the tone by payment history. For many small firms that's fine if the template is well written. Rewrite the default text using the tone rules above and you've done most of the work.
An automation with an AI step (Zapier or Make) is worth it when you want the personalised versions above. The flow: each morning, pull overdue invoices from the accounting system; skip any invoice where a reply has arrived since the last reminder, a promise-to-pay date hasn't passed yet, or the account is flagged "do not chase"; pass the facts and style samples to the AI step; send from the account manager's mailbox, or put drafts in their outbox for a quick look during the first month. Log what was sent so the next step knows the history.
For the first month, run it in drafts. The bookkeeping firm had each morning's reminders land in the account managers' draft folders, and they sent them after a quick read. In those four weeks they edited about one in eight, almost always because the client had phoned about the invoice and the system didn't know. That's the gap to close before switching to automatic sending: log phone conversations somewhere the automation can see, even as a one-line note on the contact. The pattern of drafting first and sending later is covered in more detail in adding human approval steps to AI automations.
Sorting the replies so nothing gets chased twice
Replies are where the human touch is won or lost. An AI step can read each reply and sort it:
| Reply type | Example | What happens |
|---|---|---|
| Paid | "Paid this morning" | Pause reminders for 3 working days; check the bank feed |
| Promise to pay | "Will go in Friday's run" | Record the date; no reminder until the day after |
| Query or dispute | "We didn't get the payroll run in August" | Stop the sequence; task for the account manager today |
| Cash-flow difficulty | "Things are tight, can we spread it?" | Stop the sequence; account manager calls to discuss a plan |
| Wrong person | "I've left, try accounts@" | Update the contact; resend reminder 1 to the new contact |
If replies come into a shared accounts inbox rather than personal ones, the same sorting step can tag and route them alongside everything else that arrives there; triaging a shared inbox with AI shows how to set that up without replies getting lost between people.
A promise to pay is the reply most often mishandled. If Friday passes without payment, the next email should say so plainly: "You mentioned this would go in Friday's run, but I can't see it yet. Has something held it up?" Acknowledging the promise shows a person is paying attention; ignoring it and sending reminder 3 shows the opposite.
The phone call and the final notice
At day 21, the account manager calls. AI helps here too, by preparing a short brief: the invoices outstanding, the reminder history, anything the client has said, and how they've paid in the past. An illustrative brief:
[first name] (Client 118). Two invoices, $1,440 total, 38 and 8 days
overdue. No reply to 3 emails. Previously paid within 5 days
of due date for 14 months. Last contact: 2 Sept, asked about
adding a second company. Suggest: ask if anything has changed
in the business; offer to split payment across two months.A long-standing good payer going silent is usually a sign of trouble in their business, not carelessness, and the call is a chance to agree a plan before the debt gets bigger. If the call doesn't resolve it, the final notice is a letter a person approves: the amount, the invoices, the date by which payment is needed, and what will happen if it isn't made, such as pausing work under the engagement terms. If your terms or local law give you a right to interest or fixed compensation on late business payments, this is the place to mention it, after checking what applies to you.
Fewer invoices to chase in the first place
The kindest reminder is the one you never need to send. Three changes cut the bookkeeping firm's overdue list before the new sequence even started:
- Invoices went out on the first working day of the month, not whenever someone got round to it. Clients who receive an invoice promptly treat it as current; one that arrives three weeks late feels optional. If sending on time is the problem, start with automating invoicing from finished job to paid.
- Every invoice said what it was for, in the same plain words the reminders now use, so there was nothing to query.
- Monthly-fee clients were offered direct debit or card-on-file payment at their next review. Forty-one of the 160 moved over in a quarter, and those invoices simply stopped appearing on the overdue list.
Moving regular fees onto automatic collection removes a large share of the chasing for any business with recurring clients. Reminders are then left for the one-off and variable invoices, where the personal touch matters most.
When reminders shouldn't be automated at all
- Disputed invoices. Once a client has raised a query, every automated email is a small insult. Flag the invoice "do not chase" until it's resolved.
- Sensitive situations. An illustrative law firm billing executors for work on a family member's estate doesn't send automated chasers at all; the fee earner calls. The same applies to any client you know is dealing with illness or bereavement.
- Your largest clients. An insurance broker or recruitment agency whose biggest client pays through a monthly supplier run gains nothing from automated nudges. A quarterly call with the client's accounts team to confirm invoices are approved does more.
- Payment plans. Once a plan is agreed, reminders should follow the plan's dates, not the original due date.
Measuring reminders with DSO and three quieter numbers
Track days sales outstanding (DSO): what clients owe you, divided by what you bill, multiplied by the days in the period. Before the new sequence, the bookkeeping firm was owed $46,500 at month end on $41,000 of monthly billing: 46,500 ÷ 41,000 × 30 = 34 days. Three months later (illustrative), it was owed $30,000 on the same billing, which works out at 22 days. That difference is over $16,000 of cash that sits in the firm's account instead of its clients'.
Alongside DSO, watch three quieter numbers: the share of overdue invoices paid before the second reminder (the higher, the better your first email), the share of reminders that get any reply, and complaints about reminders. One complaint in a quarter is useful feedback. Several means the tone or the timing needs another look, and it's worth reading the last twenty reminders sent, start to finish, the way a client would.
Late payment reminders: common questions
Should reminders come from a person or an accounts address?
From a person where you can, ideally the one who manages the relationship, even if the email is sent automatically. People delay paying an accounts mailbox far more comfortably than they ignore someone they know. Replies should go to that person too, so nothing lands in an inbox nobody reads.
Can I add late payment interest to a reminder?
Only if your terms allow it or the law where you operate gives you the right, and some places do for business-to-business invoices. Check both before mentioning it. Even where you're entitled to it, raise it at the final-notice stage rather than in early reminders, because it changes the tone of the relationship and many businesses waive it once the invoice is paid.
How many reminders are too many?
Four emails over about three weeks, followed by a phone call, is plenty for most business clients. Beyond that, more emails rarely work and start to irritate. If an invoice is still unpaid after the call and a final notice, the next step is a decision about the relationship, a payment plan or formal recovery, not another automated email.
Further reads
- Chasing Unpaid Invoices With AI: Polite Reminders for Trades — Reminder wording tuned for trades and home-service jobs.
- AI Accounts Receivable: Predict Late Payers and Act Early — Predict late payers so reminders start earlier for them.
- How to Draft Customer Email Replies With AI That Sound Like You — Draft other client emails in your own voice, not just chasers.
- How to Check a New Customer's Credit Before Offering Terms — Prevent late payers by checking credit before offering terms.
- ChatGPT Prompts for Bookkeepers: Client Queries, Chasers, Notes — More ready-made prompts for client queries and chasers.
- Quote to Cash: Connect Quotes, Invoices and Payments With AI — Tighten the whole chain so fewer invoices go overdue.
- AI Quick Wins: 12 Things a Small Business Can Set Up This Week — Twelve small AI jobs sorted by setup time, each with a copyable prompt, a real business example and the catch to watch for.
- AI Use Cases by Department for Small Businesses (With Examples) — 21 practical AI use cases across seven departments, each shown in a small insurance brokerage, with how to start and what to watch.
- How Freelancers Use AI for Invoices, Proposals and Chasers — One thread from proposal to payment: AI drafts the scope, checks the invoice and writes the reminders, and your invoicing software sends them on time.
- Tutoring Centre Admin With AI: Enquiries, Timetables, Invoices — Enquiry replies from a fact sheet, AI-proposed timetables checked for clashes, and invoices built from attendance: a tutoring centre's admin, step by step.
- How to Build a 13-Week Cash Flow Forecast With AI Help — A weekly cash forecast built from your bank balance, debtors, bills and payroll, with AI timing receipts by real payment habits and explaining variances.
- AI Cash Flow Forecasting Tools for Small Businesses Compared — Nine ways to forecast cash compared on what matters: weekly or monthly view, forecast horizon, what the AI actually does, integrations and list price.
- How to Get a Weekly Business Summary Emailed to You by AI — Get a Monday email with your five key numbers and a short AI commentary. Covers the numbers tab, Zapier and Make builds, assistant scheduled tasks and checks.
- How to Write Terms of Business With AI and What Needs a Lawyer — Map your trading terms clause by clause, draft the operational ones with AI, and brief a lawyer on the risky ones so the review stays short.
- AI Workflow Automation Examples: 20 Processes to Automate First — Twenty processes ranked by a 25-point score, from inbox sorting to credit packs, each with a worked example, rough costs and what to watch.
- 8 Worked AI Automations for a Service Business, With Costs — One illustrative testing laboratory builds eight automations, from enquiry logging to a Monday summary, with task counts, AI costs, setup time and what broke.
- AI Tools and AI Development: The Complete 2026 Guide — the AI hub, including every tutorial in the AI-for-business series.
Sources: Xero Central (invoice reminders: up to five on one schedule, before or after the due date, defaults at 7, 14 and 21 days overdue); QuickBooks Online help (up to three automatic reminders, up to 90 days before or after the due date; Payments AI drafting reminders for approval).