Collection Agency or AI Payment Follow-Up for Overdue Invoices

The short verdict

Use an AI payment follow-up worker for invoices that are a few days to a few weeks late. Hand accounts to an agency when the debtor has gone silent, the balance is old, or a court process is the only route left. A person should own every dispute from the first day, because a dispute changes what is legally owed. The two options are not really rivals. They sit at different points in the same cash process.

The problem is common enough to justify a permanent process. Atradius's 2025 Payment Practices Barometer for Western Europe reported that 47% of B2B invoices in that region were overdue. Its 2025 North American data, as summarised by one 2026 aggregator, put the figure for US B2B invoiced sales at 55%. Those are survey figures, not a measure of your own ledger, so pull your own aging report before deciding anything.

Side-by-side comparison

What an agency does well, and what it costs

An agency brings people who do this full time, a legal network and the willingness to chase a hard account for months. Its incentive is simple. If it recovers nothing, you owe nothing. That makes agencies useful for accounts that have stopped responding to your own emails and calls.

The headline fee is not the whole bill. SWRS notes that some agencies add a further percentage, often around 10%, when litigation becomes necessary, and that court filing fees and attorney fees are typically separate. Ask for the full fee schedule, including what happens if the debtor pays you directly after placement. Some placement agreements also restrict you from taking the account back or contacting the debtor yourself, so read those terms before signing.

What an AI payment follow-up worker does, and where it stops

An AI worker is a scheduled process connected to your invoice ledger. It sends the first reminder when an invoice falls due, a second one a few days later, and a clear statement of the balance after that. When a debtor replies with a payment date, the worker records the promise and checks it against the bank feed. When a reply says the goods were wrong or the amount is incorrect, the worker stops automatic chasing and sends the case to a named person.

The limits matter more than the features. The worker must not threaten, imply legal action it has not been authorised to take, or pressure a debtor by repeated calls at unreasonable hours. Disputes and final demands need a person and the right legal process. In the UK, the Late Payment of Commercial Debts (Interest) Act 1998 sets statutory interest at 8% above the Bank of England base rate, and a 2026 legal guide notes that contract terms can vary that right only with a substantial remedy. Whether to claim it is a legal decision, not a message template. Also note that disputed amounts usually do not trigger the Act until the dispute is resolved under the contract, as a Lexology commentary on a court case explains.

Regulation differs by country. In the United States, the Fair Debt Collection Practices Act covers consumer debts and generally does not apply to business invoices, while state laws such as California's Rosenthal Act can extend protections to commercial debts. Agencies and software vendors both need to follow those state rules, so do not assume that a business-to-business label means no rules apply.

Who each option suits

A five-person consultancy with fifty open invoices and a handful of slow payers will usually get more value from an AI worker for the reminder stage, plus a fixed monthly agreement with an agency for the few accounts that go bad. A group with thousands of staff and several billing entities may need both, with the AI worker reporting to a central receivables team and agencies placed under strict rules for each entity.

An agency is the better fit when the debt is old, the debtor is in another legal territory, the amount justifies legal costs, or you do not have anyone internal who can handle calls and letters. An AI worker is the better fit when most of your problem is volume: many invoices that are late by days, not months.

Total cost of ownership beyond the sticker price

• Contingency share and legal add-ons. A 15% share on a recovered invoice is only the start. Add litigation percentages, court fees and any internal time spent on documents.
• Usage charges. Chaser's published add-ons for SMS, automated calls, letters and credit checks are billed on top of the plan, according to a 2026 pricing review.
• Maintenance of a custom build. Accounting systems change, templates need updating and integrations break after upgrades. Budget for someone to own that work.
• Breakage. An AI worker that sends a reminder to the wrong contact, or ignores a dispute flag, can cost more than the late fee it was meant to protect.
• Exit costs. Check whether you can export reminder history, promise records and templates. Agencies may charge to recall accounts. Software vendors may lock histories inside their portal.
• Staff time on exceptions. Neither option removes every call. Estimate how many replies a week will need a person.

The custom-built alternative and when it wins

A custom AI payment follow-up worker is built around your own ledger, rules and approval steps. It wins when your billing logic is unusual, when your accounting system is one that the off-the-shelf tools do not support well, when you want the data held in a specific country, or when you already have the internal skills to maintain it. It loses when you need a product live in a few weeks, lack someone to maintain it, or have too few invoices to justify the build.

The build cost is not public for any vendor in this comparison, and it depends on the number of systems, the complexity of your terms and how much human review you keep. Ask for a fixed scope and a written maintenance plan before signing anything.

Migration notes

1. Export an aging report from your ledger. Sort invoices into groups by days overdue and by whether a dispute is open.
2. Decide the handover point. Many businesses keep reminders in-house until a fixed number of days, then move the account to an agency or a legal review.
3. Stop placing new accounts with the agency that you are replacing, and check the placement agreement for recall terms and any fees.
4. Pilot the AI worker on one customer segment. Review every reply that mentions a dispute, a payment plan or a complaint.
5. Keep an audit trail of every reminder, promise and escalation. That record is what you will need if a debtor or a court later questions your process.
6. Confirm your standard payment terms and any interest wording with a lawyer in each country you invoice in.