A late fee only works if the client agreed to it before the work started and sees it on every invoice. Here are three pieces of wording to copy: one for your contract, one for your invoice, and one email for when a payment is actually late. Fill the brackets and adjust the numbers to what you're comfortable enforcing.
Put this in your proposal or agreement before work begins
Payment terms: Invoices are due [14] days from the invoice date. Payments received after the due date incur a late fee of [X]% of the outstanding balance per [month], or the maximum allowed by law, whichever is lower. Work may pause on any account more than [14] days overdue until the balance is paid.
On every invoice, right under the total
Due [date]. Per our agreement, a [X]% late fee applies to balances unpaid after [date]. Pay securely at [payment link].
When the due date has passed and a friendly reminder went unanswered
Subject: Invoice [#]: late fee applied Hi [Name], Invoice [#] for $[amount] was due on [date]. As outlined in our agreement, a [X]% late fee of $[fee] has now been added, bringing the balance to $[new total]. The updated invoice is attached. If the payment is already on its way, let me know and I'll keep an eye out. If something has come up, reply and we can agree on a plan. I'm happy to waive the fee if the original amount is paid by [date]. Thanks, [Your name]
The Invoice + Payment Chase Pack covers the whole cycle: payment-terms snippets, a follow-up sequence from friendly reminder to final notice, and an invoice tracker with an aging checklist.
Get the Invoice + Payment Chase Pack ($19) Get-Paid Bundle: proposal + scope + invoice ($49)Use Claude, Cursor or Codex? The Invoice Chase AI agent skill ($12) drafts the right follow-up for each overdue invoice.
Grab the 3 free emails that get unpaid invoices paid, the client ghosting follow-ups, the scope creep scripts, or the free client follow-up tracker.