How it is calculated
Simple interest: fee = amount × annual rate × days ÷ 365. With a monthly rate, the rate is applied per 30 days. Some contracts add a flat recovery fee on top.
Late payment fee calculator
Work out the late fee on an overdue invoice from the amount, an annual or monthly rate, and the number of days past due.
Overdue amount10,000.00
Late fee / interest98.63
Total now due10,098.63
Be reasonable and check the law
Late fees must usually be agreed in your terms and may be capped by law. Rates change and rules differ; verify with the tax authority or an accountant.
Questions
Can I charge interest on any late invoice?
Only if your terms or the law allow it, and the rate may be capped.
Is it simple or compound interest?
Simple, which is how most invoice terms are written.