Late Payment Interest Calculator

Most freelance contracts contain a late-fee clause that is never used. Part of the reason is that the number feels abstract — 1.5% per month on an unpaid invoice does not sound like leverage until it is written as a dollar figure on a statement.

This works out what your own clause has accrued. Send the result as a line on the next statement rather than as a threat; an invoice that grows on its own schedule tends to get paid before one that sits still.

Before you charge it

• The clause has to exist. Interest cannot be invented after the fact. If your contract is silent, this is a negotiation, not an entitlement.
• Send a statement, not a lecture. Principal, interest, daily accrual, and a payment link. No adjectives.
• Be willing to waive it. Offering to drop accrued interest in exchange for payment this week closes more invoices than the interest ever collects.

When it stops working

If two statements go by without contact, the problem is not the fee — it is that the client cannot or will not pay. At that point the question becomes whether pursuing it is worth the hours, which is a different calculation.