How to chase overdue invoices with AI without losing the customer

Somewhere in your accounting software there is a list of invoices that are past due, and you have been meaning to deal with it. Most owners have that list. The awkward part is rarely the maths. It is writing the email that gets you paid without souring a customer you want to keep.

The numbers say you are not alone. Xero's small business data put the average Canadian small business at 11.6 days late in the first quarter of 2026, after an average wait of 29.8 days. Atradius's 2024 survey of Canadian firms found that 46% of B2B invoices were overdue on average, and 6% ended up as bad debt.

This guide is for anyone who sends invoices to other businesses and wants a calmer routine. You need accounting software that can email invoices (QuickBooks Online, Xero or similar), a free or paid AI assistant, and about an hour to set it up. Nothing here needs code.

Sort out what software does and what AI does

Reminders are a scheduling job, and your accounting software already does scheduling. QuickBooks Online can send up to three reminders per invoice, set anywhere from 90 days before to 90 days after the due date, and only for unpaid invoices you have already emailed. Xero's Canadian invoicing also sends reminders before or after the due date.

AI earns its place elsewhere: writing the words. An assistant can turn "pay up" into three polite versions in different tones in ten seconds.

The usual mistake here is asking the AI to do both and then having no record of what was sent. Keep the sending inside your accounting software so every reminder is logged against the invoice.

Write three messages for three stages

Xero's guide suggests a staged approach: a friendly nudge at 1 to 3 days overdue, a formal follow-up at 7 to 14 days, and a written demand at 30 days or more. Ask your AI tool for one message per stage. A prompt that works:

Write a short, friendly email reminding a business customer that invoice [number] for [amount] was due on [date]. Plain Canadian English, two or three sentences, no guilt-tripping, and a line saying they can reply if there is a problem with the invoice.

Then ask for the formal version (firmer, restates the due date and payment options) and the 30-day version (states that further action may follow, without threats). Edit each until it sounds like you.

The usual mistake is a message that sounds written by a lawyer on day one. A customer who forgot is not an enemy.

Put the messages into your reminder templates

In QuickBooks, reminders live under Settings, then Account and settings, then Sales, then Reminders. You can edit the subject line and message, and use variables such as the invoice number and company name so each email fills itself in. Paste your friendly, formal and firm messages into the three slots and attach the invoice PDF.

Xero's guide also recommends putting the invoice number and due date in the subject line and including a direct payment link. Do that, and the customer has nothing to look up.

Keep a person in charge of the hard cases

Some invoices are not forgetfulness. The customer disputes the work, is short of cash, or has gone quiet. A scheduled email does not know that. Check your overdue list weekly and phone anyone past the second stage. A five-minute call often settles what three emails would not.

Do not let AI send the 30-day demand on its own. Read it, check the amounts, and send it yourself. If you are considering legal action or a collection agency, speak to a lawyer first; the rules on collecting debts in Ontario are a legal question this post does not try to answer.

Agree late fees before the job, not after

Xero's guide says late fees or interest must be agreed before work begins and cannot be added retroactively. It describes 1% to 2% per month as a common approach, and says the clause should state the rate, when it starts, and whether it compounds. An AI assistant can help you draft that clause for your quote template. Have your lawyer or accountant read it once before you use it.

The usual mistake is adding a fee to an old invoice and hoping nobody objects. That is how you lose a good customer over $40.

Protect your customers' information

A reminder needs an invoice number, an amount and a date. It does not need a customer's phone number, address or the story behind the delay. Paste only what the message needs. Check whether your AI tool uses your inputs for training, and switch that off if it does. If you handle information about individuals, PIPEDA applies to how you use it, so your privacy officer or accountant should be able to say where to draw the line.

Know what it costs, and what it does not fix

The software side may cost nothing extra. QuickBooks' help page does not say which plans include automatic reminders, so check your own plan before you count on them. I could not confirm current Canadian prices for either QuickBooks or Xero, so look at their pricing pages rather than trusting a number here. A free AI assistant is enough for drafting three short emails.

What this routine does not fix is a customer who cannot pay, or one who never agreed to your terms. For those, the better tool is a written agreement and a deposit up front.

A simple schedule shows how the pieces fit. This is an illustration, not a client result:

Common mistakes

• Sending the same reminder at every stage. The tone should change.
• Letting software send the final demand unseen.
• Chasing a customer who has a legitimate dispute. Fix the dispute first.
• Pasting full customer records into an AI chat.
• Skipping the phone call.

Where to start

1. This week, list your five oldest unpaid invoices and phone the owner of the oldest.
2. Ask an AI assistant for the three-stage messages above and load them into your accounting software's reminders.
3. Add a payment-terms and late-fee line to your next quote, and have it checked once.

If you would rather have someone set up the reminders and review the wording with you, you can book a call with Trimotech.