Estimate what an overdue invoice has accrued: days late, a flat fee, a monthly late charge and annual interest, with the total now due.
Days late counts from the due date to the payment or as-of date. The monthly late charge is applied per month or part of a month: a payment 31 days late counts as two months, charged simply on the original invoice amount rather than compounded. Interest accrues day by day at the annual rate divided by 365. A flat fee applies once if the invoice is late at all. The result is an estimate — actual late terms depend on the contract or the terms printed on the invoice, and some jurisdictions cap what can be charged.
How is the monthly late charge counted? Per month or part of a month: any started month counts in full, charged simply on the original invoice amount. One month and one day late counts as two months.
Is this figure legally binding? No. It is an estimate from the figures entered. Enforceable late fees depend on the contract, the invoice terms and local law, which can cap rates.
What if the invoice was paid on time? With zero days late, the flat fee, monthly charge and interest all come out at zero and the total due equals the invoice amount.