Invoice Late Fee Calculator
Calculate exactly how much a client owes when an invoice is paid late.
How do invoice late fees work?
A late fee is an additional charge added to an unpaid invoice once it passes its due date, meant to compensate the business for delayed payment and encourage clients to pay on time. Late fee terms should always be stated clearly in the original invoice or contract before work begins — charging a surprise late fee after the fact is both bad practice and, in many jurisdictions, unenforceable.
Flat percentage vs. monthly interest rate: what's the difference?
A flat percentage late fee is a one-time charge (for example, 5% of the invoice) that applies as soon as the payment is late, regardless of how many additional days pass. A monthly interest rate, by contrast, compounds or accrues based on how long the invoice remains unpaid — a 1.5% monthly rate on an invoice that's 45 days late would apply for 1.5 months' worth of interest, not just one flat charge. Monthly interest structures are more common for larger invoices or long-standing client relationships where payment delays can stretch on for months.
Are there legal limits on late fees?
Yes — many US states cap the interest rate businesses can charge on overdue invoices, and some industries (like construction) have specific prompt-payment laws. A common commercial rate is 1-1.5% per month (roughly 12-18% annually), which tends to stay under most usury limits, but it's worth checking your state's rules or your contract's governing law before setting a rate.
Frequently Asked Questions
What's a typical late fee percentage for invoices?
Common late fee rates range from 1% to 1.5% per month, or a flat 5-10% one-time fee. The right rate depends on your industry, contract terms, and any state-level interest rate caps.
Can I charge a late fee if it wasn't mentioned on the original invoice?
Generally no — late fees are only enforceable if they were disclosed in the contract or invoice terms before the work was completed. Adding a surprise late fee after the fact is likely unenforceable and can damage the client relationship.
Does the late fee keep growing the longer the invoice goes unpaid?
Only if you're using a monthly interest rate structure — the fee accrues based on how many months (or partial months) have passed. A flat percentage fee is a one-time charge that doesn't increase with time.
Is there a legal maximum late fee I can charge?
Many US states impose usury limits on interest rates that can apply to late fees. Rates of around 1-1.5% per month tend to stay under most state caps, but you should verify the rules that apply in your state or your client's.
How do I calculate late fees for partial months?
Most businesses use a decimal number of months rather than rounding — for example, 45 days overdue is treated as 1.5 months, not rounded up to 2. This calculator uses that same decimal approach.
Should freelancers charge late fees on every overdue invoice?
Not necessarily — many freelancers reserve late fees for chronically late clients and waive them for occasional, brief delays from otherwise reliable clients. It's a business relationship decision as much as a financial one.
What should I include in my invoice's late fee policy?
State the grace period (if any), the exact rate or flat percentage, whether it's a one-time charge or accrues monthly, and when the fee starts applying — all clearly written before the client agrees to the work.
Does charging a late fee affect my chances of getting paid at all?
It can go either way — a clear, professionally worded late fee often motivates faster payment, but an aggressive fee on a client who's already struggling to pay might not be collectible in practice. Consider the relationship and likelihood of payment before enforcing steep fees.