How late fees are calculated
The standard approach is simple monthly interest, pro-rated by day: invoice amount × monthly rate × (days overdue ÷ 30). At the common 1.5% per month, a $2,500 invoice that's 30 days late accrues $37.50 — not a windfall, but it changes client behavior, which is the real goal.
Some freelancers use a flat late fee (for example, $50 after 7 days) instead of interest. Flat fees are simpler to communicate but interest scales with the invoice size, which matters on larger projects.
Making late fees enforceable
A late fee is only collectible if the client agreed to it before the work happened — it needs to appear in your contract or on the invoice terms the client accepted, not just on the overdue notice. Many jurisdictions also cap interest rates, so confirm the maximum where you or your client operate before setting a rate above the typical 1–2% per month.
In practice, the fee's biggest value is leverage: many freelancers waive it once the client pays promptly, using the waiver as goodwill while still training the client to take due dates seriously.
Frequently asked questions
- What's a standard late fee for freelancers?
- 1.5% per month (18% per year) is the most common rate in the US. Some charge 1% to stay conservative, and some use a flat fee instead. Check local usury caps before going higher.
- Can I charge a late fee if it wasn't in my contract?
- Generally no. Late fees must be agreed in advance — in the contract or on invoice terms the client accepted. Adding one retroactively to an overdue invoice is usually unenforceable.
- When does the clock start on a late payment?
- The day after the due date stated on the invoice. If your terms are Net 30 and you issued the invoice on March 1, interest starts accruing on March 31.