1. Check the facts before the tone
Confirm the invoice number, unpaid amount, due date, contact address and payment details. Check whether the client raised a genuine dispute or needs a purchase-order number. A correct reminder is more effective than an aggressive one.
2. Assume admin delay once, not forever
Your first message can be warm and neutral: the invoice is overdue, here are the identifying details, and here is the action required. Avoid apologising for asking or burying the request under small talk.
3. Make payment or explanation the obvious next move
Attach the invoice, repeat the bank or payment details, and ask for either payment confirmation or a specific explanation. “Please let me know” is weaker than “Please confirm today when payment will be made.”
4. Give the next date
If the invoice remains unpaid, move from an open-ended reminder to a dated follow-up. State when you will check again. Keep the timeline proportionate and do not threaten action you are not prepared to take.
5. Mention charges accurately
For an eligible UK commercial debt, statutory interest and fixed recovery compensation may be available. Calculate the amount first, check the contract and relevant reference rate, then decide whether to claim it now or reserve the right to do so.
Useful rule: polite means respectful and clear. It does not mean vague, apologetic or indefinite.
When to become firmer
If there is no reply after the first reminder, send a shorter message that refers to the earlier contact, repeats the amount and requests a payment date. Keep a copy of every message and attachment. If the debt is disputed or formal recovery is being considered, seek appropriate advice.