What does a late invoice actually cost?

Yes. In the UK, the Late Payment of Commercial Debts Act gives you the right to charge statutory interest on overdue invoices without it needing to be in the original contract. In the US, you can include late payment terms in your contract and charge accordingly. Most agencies do not enforce this, but the legal right exists. This calculator shows you the cost so you can make an informed decision about whether to pursue it.

Scope creep is the cost of extra work you delivered but did not charge for. An invoice delay is the cost of money you billed for but have not yet received. Both erode your margin — one through unbilled effort, the other through trapped capital. This calculator covers the second type. The Scope Creep Calculator on this site covers the first.

It uses the standard opportunity cost methodology: the cost of capital tied up in an unpaid invoice equals what that money could have earned if it were in your account. The 10% annual rate is the recognised benchmark for small business own-reserves cost of capital. If you are borrowing to cover cash flow, the credit line mode uses your actual interest rate instead. Results are as accurate as the numbers you enter.

This calculator shows you the cost of a scenario you enter manually, right now. MinuteMargin tracks every outstanding invoice across all your active projects in real time, so you see the running cost as it accumulates — without having to calculate it yourself each time. It also connects invoice delays to the specific project and client that caused them, so you can act on the data rather than just observe it.