The work was delivered, the invoice went out, and nothing has happened since. NETTERMS does the arithmetic on your payment terms, tells you how overdue you actually are, and drafts the message that fits the stage you have reached, from a courtesy note through to a formal demand letter. Nothing you type here leaves the tab.
This is drafting help, not legal advice, and nobody here is your lawyer. The templates are general: what you can actually claim, whether you are entitled to interest and at what rate, how much notice you must give, and what a demand letter needs to say all depend on your contract and on where you and your client are. Several places have statutory late-payment rules that are more favourable than anything you would think to ask for, and some contracts override them. Read what you send before you send it, put in your own facts, and take proper advice before starting any formal process. The interest figure here is simple interest on the outstanding amount at the annual rate you enter, worked out from the due date; it is a starting point for a conversation, not a calculation you should rely on in a filing.
Questions people ask
What can I do when a client will not pay an invoice?
Escalate in writing, in steps. A polite reminder, then a firm one restating the agreed terms and the amount, then a formal letter before action giving a deadline and saying what follows if it passes. Each step should name the invoice number, the date, the terms and the days overdue. Most invoices are paid at the second or third step.
Can I charge interest on a late invoice?
In many places yes, either at a rate written into your contract or at a statutory rate set by law, and in the UK and EU there is also a fixed compensation sum per invoice. The entitlement often exists whether or not you mentioned it in the contract. This is not legal advice, and both the rate and the right depend on where you and the client are.
What is a letter before action?
The last letter before a claim. It sets out what is owed and why, encloses the evidence, gives a clear deadline, and states plainly that proceedings will follow if the deadline passes. Courts expect to see one, and sending a proper one very often ends the matter without a claim.