Invoice Late Payment Interest Calculator
Calculate exactly what a late-paying client owes in interest.
Open the Interactive CalculatorHow It's Calculated
Late Fee = Invoice Amount × (Annual Rate ÷ 365) × Days Late.
Example
Example: a $5,000 invoice paid 30 days late at an 18% annual late-fee rate accrues about $74 in late fees — for a total due of $5,074.
Frequently Asked Questions
Is charging a late fee legal?
Generally yes if disclosed in your contract or invoice terms in advance — rates and rules vary by state, so check local regulations for caps.
Can I charge compound interest on late invoices?
This calculator uses simple daily interest; some contracts specify compounding, which would accrue slightly more over long periods.