How to chase an unpaid invoice

Most late invoices are not disputes. They are an email sitting unread in an accounts inbox, or a payment run that happens on the 25th regardless of what your terms said. The difference between getting paid in week five and week twenty-five is usually not how forcefully you chase — it is whether you escalate on a fixed schedule instead of waiting to feel annoyed enough.

Before you chase, check your own paperwork

Roughly a third of "late" invoices are late because of something on the supplier's side. Spending ten minutes here saves you from sending an aggressive reminder about an invoice that never reached anyone.

Did it go to the right address? Many companies pay only from an accounts inbox. An invoice sent to your day-to-day contact may never have been forwarded.
Does it carry a PO number? If the client uses purchase orders, an invoice without a valid PO is often rejected automatically and silently.
Is the due date actually passed? "Net 30" from the invoice date and "30 days end of month" can differ by six weeks. Check which one you agreed to.
Are your bank details on it? Obvious, and it still happens.
Did you send a statement of work or accepted quote? If the amount is being queried, the accepted quote is the document that settles it.

Log the date you sent it. Every stage below is measured from the due date, and if this ever reaches a formal claim you will need the timeline. Keep the sent email, not just the PDF.

The five-stage escalation ladder

Fix the timing in advance and follow it regardless of mood. The value of a ladder is that each rung is unremarkable on its own — you are never making a scene, you are just doing the next scheduled thing.

Day 1 after due date — the assumption-of-innocence nudge A short, friendly email that assumes it was missed, because it usually was. Re-attach the invoice rather than referring to it. Ask one direct question: can you confirm this is scheduled for payment, and if so for what date? A question needs an answer; a statement does not.
Day 7 — the reminder that names a person Reply on the same thread so the history is visible, and copy in someone new: the person who hired you if you have been talking to accounts, or accounts if you have been talking to your contact. Nothing changes the speed of an invoice like a second person seeing it. State the amount, the due date, and how many days overdue it now is as a number.
Day 14 — the phone call Email is easy to defer; a call is not. Ask specifically: is the invoice approved, is it in a payment run, and which run. Then send a short email summarising what was agreed on the call. That summary email becomes your evidence.
Day 30 — the formal notice Tone changes here. Written, dated, referencing the invoice number and the contract or accepted quote. State the total now due, note that late payment interest is accruing (see below), and give a specific deadline — seven or fourteen days — after which you will begin recovery. Say plainly what recovery means. Do not bluff about a step you are not prepared to take.
Day 45+ — recovery Small claims, a solicitor's letter, or a debt collection agency. Which one depends on the amount and your jurisdiction. In most places, claims below a few thousand are designed to be filed without a lawyer.

What to actually write

The most common mistake is over-explaining. A chase email should be short enough to read on a phone in five seconds, and should contain a question with a date in it. Apologising for chasing invites another delay; you are not asking for a favour.

A workable stage-two email is roughly: the invoice number and amount, the due date, the number of days overdue, one sentence asking for a confirmed payment date, and the attachment again. That is all. Long emails read as negotiable.

At stage four the register changes from asking to notifying. You are no longer asking when they intend to pay; you are telling them what happens next and when. Keep it unemotional — a formal notice that reads as angry is easier to dismiss than one that reads as procedural.

Charging interest and compensation

In much of the world you have a statutory right to charge interest on late commercial payments, whether or not your contract mentions it — and in some places a fixed compensation sum on top. This is covered in detail in the guide to late payment fees and interest, but the short version:

UK: the Late Payment of Commercial Debts (Interest) Act 1998 gives a statutory interest rate of 8% above the Bank of England base rate on business-to-business debts, plus a fixed compensation amount that scales with the size of the debt.
EU: Directive 2011/7/EU sets a floor of 8 percentage points above the European Central Bank reference rate, plus a minimum recovery amount of €40, implemented in each member state's own law.
US: there is no general federal late-payment statute for private contracts. Late fees are enforceable only if your contract provides for them, and state usury laws cap how much you can charge.
Canada and Australia: largely contract-driven for ordinary B2B work, with specific statutory regimes in construction.

Two practical notes. First, you can invoke a statutory right without having invoiced for it in advance — mentioning it in a stage-four notice is normal and legitimate. Second, many suppliers waive the interest once the principal is paid, and say so explicitly when they do; that is a reasonable commercial choice, but make it deliberately rather than by forgetting.

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When the client is disputing, not stalling

A genuine dispute needs the opposite approach. Escalation ladders are for silence; a disputed invoice is a conversation, and pushing the ladder on it will cost you the relationship without speeding anything up.

Get the objection in writing. A vague "we're not happy with it" cannot be resolved. Ask which line item and what specifically is wrong.
Separate the disputed part. If four of five line items are agreed, ask them to pay those now and keep the disagreement to the fifth. Most clients accept this, and it stops one contested item holding the whole amount hostage.
Go back to the accepted quote. If the work matches what was approved, that document is the answer. If the work exceeded it and you never got the extra approved in writing, that is a lesson for next time and probably a partial write-off this time.

What not to do

Do not stop mid-ladder. Chasing twice and then going quiet teaches the client that your deadlines expire. It is worse than not chasing at all.
Do not threaten a step you will not take. If you announce legal action at day 30 and are still emailing at day 90, every future deadline you set is noise.
Do not withhold deliverables you have already been paid for. Depending on your contract and jurisdiction this can put you in breach, and it converts a simple debt into a two-sided argument.
Do not vent publicly. It rarely accelerates payment and it is visible to every future client who searches your name.

Reducing how often this happens

Chasing is a symptom. The structural fixes sit earlier in the process: taking a deposit so you are never fully exposed, invoicing on the day work completes rather than at month end, billing long projects in milestones, and confirming the accounts contact before the first invoice rather than after the first late one. Those are covered in getting paid faster.

Common questions

How long should I wait before the first chase?

Send it the day after the due date. Waiting a week to be polite mostly signals that your due dates are approximate. The first message can be warm and still be prompt.

Can I add a late fee that wasn't on the original invoice?

If you are relying on a statutory right — as in the UK or EU — that right exists independently of what the invoice said, so yes. If you are relying on a contractual late fee, it needs to have been in the agreed terms. Adding a purely contractual fee after the fact is generally not enforceable.

Should I keep working while an invoice is overdue?

Check your contract first, since stopping work can itself be a breach. If you have the right to pause, say so before you do it rather than going silent, and put it in writing. Continuing to deliver while unpaid increases your exposure with every hour.

Is a debt collection agency worth it?

Agencies typically take a percentage of what they recover, often substantial. For small amounts the fee can approach what you are owed. They make more sense for larger debts, or where you have decided the client relationship is finished regardless.

What if the client has gone insolvent?

Escalation stops being useful. You become a creditor in a formal process and will need to register your claim with the appointed insolvency practitioner. Unsecured suppliers usually recover little, which is the strongest practical argument for deposits on large jobs.

This is general information, not legal advice. Statutory rates, compensation amounts and thresholds change, and the rules differ substantially by country and by contract. Confirm the current position in your own jurisdiction, or take advice, before relying on a specific figure.

Related guides

Late payment fees and interestWhat you can legally charge, and where
Invoice payment terms explainedNet 30, EOM, 2/10 and what they cost you
Getting paid fasterDeposits, milestones and retainers
What to include on an invoiceThe fields that make it a valid record