Following Up Overdue Invoices with AI: Scripts That Get Paid Without Burning the Relationship

Around $115 billion in overdue invoices sits unpaid across Australian small businesses at any given time. That figure comes from Xero’s 2023 research, which found that 53% of invoices issued by small businesses are paid late, with an average of 6.3 days past due. For a business running on tight cash flow, one bad month of late payers can mean the difference between making payroll and not.

Most owners know they should follow up sooner. They don’t, for a simple reason: the follow-up email is uncomfortable. There’s a real fear that pushing too hard will damage the relationship, and that fear is usually enough to delay the first message by two or three days. Then another week. Then it becomes a debt collection problem instead of an accounts receivable one.

AI doesn’t feel that discomfort. You can use it to write follow-up sequences that are firm, professional, and calibrated to the situation, and then adapt them to your own voice before you send. This post gives you a practical 3-step sequence you can use this week, with real prompts and example outputs.

Why most follow-ups don’t work

The three most common failure modes in invoice follow-up:

Too apologetic. “I’m so sorry to bother you, but I was just wondering if maybe you’d had a chance to look at…” The client reads this as optional. If you sound like you don’t expect to be paid, you won’t be.

Too aggressive, too fast. Leading with late fees and legal threats on day two of overdue is likely to create conflict where a polite reminder would have resolved things quietly. Most late invoices are late because of admin error, a slow approval chain, or a busy week, not because the client doesn’t intend to pay.

Never sent at all. The worst option. A study published in the Harvard Business Review found that the single strongest predictor of getting paid on time is following up within 48 hours of the due date. Every day you wait, the probability of payment drops.

The right approach is a graduated sequence: professional and friendly early on, progressively direct as time passes, clear about consequences at the end. Here’s how to build one with AI.

The 3-step AI sequence

Step 1, Day 1 overdue: the gentle reminder

This message assumes good faith. The client probably just forgot, or the invoice got lost in someone’s inbox. Keep the tone warm. No mention of late fees. Just a nudge.

Prompt you can use:

Write a short, professional invoice follow-up email. The invoice is for $[AMOUNT] (Invoice #[NUMBER]), due on [DATE], now one day overdue. The client is [CLIENT NAME], who I’ve worked with for [X years/months]. Keep the tone friendly and assume it’s an oversight. Include the invoice amount, due date, and my bank details: [BSB/ACCOUNT]. No mention of late fees. Sign off as [YOUR NAME] from [YOUR BUSINESS]. Two paragraphs maximum.

Example output:

Subject: Invoice #1042, just a quick follow-up

Hi Sarah,

I hope your week’s going well. I’m just following up on Invoice #1042 for $2,400 (ex GST), which was due on 15 June. It may have slipped through the cracks, these things happen. You can pay by direct transfer to BSB 062-000, account 12345678 (reference: INV1042).

Let me know if you need me to resend the invoice or if anything’s unclear. Happy to help.

Cheers,
Jamie
Hartfield Creative

Customise the amount, dates, and sign-off. The tone is intentionally light, this is a nudge, not a demand.

Step 2, Day 7 overdue: the firm follow-up

If there’s no response after a week, the tone shifts. Still professional, but direct. No apology for following up. This message acknowledges that you’ve already reached out once and signals that payment is genuinely expected.

Prompt you can use:

Write a firm but professional invoice follow-up email. This is the second follow-up, the invoice is now 7 days overdue. Invoice #[NUMBER] for $[AMOUNT] (ex GST), originally due [DATE]. I sent a reminder on [DATE OF FIRST EMAIL] but haven’t received a response or payment. The tone should be direct and professional, no apologising for following up. Include my payment details: [BSB/ACCOUNT]. Mention that if there’s an issue with the invoice, I’m happy to discuss. Sign off as [YOUR NAME] from [YOUR BUSINESS].

Example output:

Subject: Invoice #1042, 7 days overdue, please advise

Hi Sarah,

I’m following up again on Invoice #1042 for $2,400 (ex GST), now seven days past its due date of 15 June. I sent a reminder on 16 June but haven’t heard back.

Please arrange payment to BSB 062-000, account 12345678 (reference: INV1042) at your earliest convenience. If there’s a question about the invoice or you need to discuss payment timing, I’m happy to talk, just reply or call me on [YOUR NUMBER].

Regards,
Jamie
Hartfield Creative

“Please advise” in the subject line does real work here, it’s professional shorthand for “respond to this.” It also signals that you’re tracking it.

Step 3, Day 14 overdue: the final notice

Two weeks past due with no payment and no contact means this is now a cash flow problem. This message is clear about consequences. You can offer a payment plan here if the amount warrants it, but the message needs to communicate that inaction has a cost.

Prompt you can use:

Write a final notice email for an unpaid invoice. Invoice #[NUMBER] for $[AMOUNT] (ex GST) is 14 days overdue. I’ve sent two previous reminders (on [DATE 1] and [DATE 2]) with no response. The tone should be formal and direct. Mention that I will be charging a late payment fee of [X%] per month if payment isn’t received within [X] business days. Offer a payment plan as an alternative if needed. State that I will escalate to debt recovery if not resolved. Include payment details: [BSB/ACCOUNT]. Sign off as [YOUR NAME] from [YOUR BUSINESS].

Example output:

Subject: Invoice #1042, FINAL NOTICE, action required by 30 June 2026

Dear Sarah,

Invoice #1042 for $2,400 (ex GST) remains unpaid, now 14 days past its due date of 15 June 2026. I have sent reminders on 16 June and 23 June, with no response received to either.

Please arrange payment in full by 30 June 2026 to BSB 062-000, account 12345678 (reference: INV1042). If full payment is not possible by this date, please contact me urgently to discuss a payment plan.

Please be advised that a late payment fee of 1.5% per month will apply to outstanding balances from this date. If this matter is not resolved by 30 June, I will refer it to a debt recovery service.

Regards,
Jamie
Hartfield Creative
[PHONE] | [EMAIL]

The FINAL NOTICE subject line is intentional, it prompts action from whoever handles accounts, even if Sarah herself hasn’t been reading her emails. Include a specific deadline. “As soon as possible” doesn’t work; “by 30 June” does.

Adapting this for the Australian context

A few things worth knowing before you start charging late fees or threatening escalation.

GST and late fees. Late payment fees are generally treated as a separate supply for GST purposes. If you’re charging a late fee, the fee itself is taxable, you need to issue a tax invoice for it. Keep it simple: state the fee as an ex-GST amount and include GST separately, just as you would on the original invoice. Check with your accountant if you’re unsure.

For larger amounts, consider PPSR registration. The Personal Property Securities Register (PPSR) lets you register a security interest over goods you’ve supplied but haven’t been paid for. If a client goes into administration while owing you money, a PPSR registration can put you ahead of unsecured creditors. This is most relevant for tradespeople, suppliers, and manufacturers dealing in goods, not professional services. Registration costs $7.40 for a 7-year term and takes about 10 minutes at ppsr.gov.au.

Small claims as a backstop. If a debt remains unpaid and the amount is under $20,000, the Victorian Civil and Administrative Tribunal (VCAT), or its equivalent in your state, offers a low-cost formal resolution path. Filing fees are modest, no lawyers required. It’s not a fast process, but it’s a real option and worth mentioning in a final notice email.

Note: This is not legal advice. For specific debt recovery questions, speak to a legal professional.

If you want a deeper look at handling overdue accounts in Australia, we’ve also covered this in our AI Upgrade guide on late invoice follow-ups, which goes into the accounting software side in more detail.

Tools that make the sequence easier

You don’t have to write and send these manually every time. Several tools can automate or partially automate the sequence.

Xero has built-in invoice reminders, you can set automated emails to go out at specific intervals before and after the due date. The templates are basic, but they work. If you’re already on Xero, this is the lowest-friction starting point. You can use the AI-generated drafts above to rewrite the Xero templates.

MYOB has similar functionality through MYOB Business, with automated payment reminders configurable by days overdue. Again, you can drop your AI-written copy in as the email template.

Ignition is an Australian-built proposal and billing platform that includes a full automated collections sequence. It’s more expensive than Xero or MYOB’s built-in tools (from around $69/month AUD), but it handles the full lifecycle: proposal, contract, payment collection, and follow-up. Worth the cost if you’re in professional services and billing regularly.

ChatGPT or Claude slot in alongside any of these tools as the drafting engine. Use them to write or personalise your templates before pasting them into your accounting software. You can also use them to handle one-off situations, an unusual client relationship, a disputed amount, a partial payment, where a canned template won’t quite fit.

One more thing

The best follow-up is a fast one. Set a calendar reminder the day an invoice goes out: if no payment in five days, send Step 1. Don’t wait until you’ve already noticed it’s overdue. By then, you’re already behind.

Most late invoices get paid after the first follow-up. The relationship fear is almost always worse than the reality.

Sources

• Xero, Small Business Insights: Invoice Payment Report, 2023, xero.com/au/resources/small-business-insights
• Harvard Business Review, “The Fastest Way to Get Paid”, 2022, hbr.org
• Australian Financial Security Authority, PPSR registration guide, ppsr.gov.au
• ATO, GST and late payment fees, ato.gov.au

This post is part of the AI Customer Ops series, AI-powered scripts and systems for Australian small business customer communications.

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