Invoice Due Date Calculator

Invoice due date calculator

Use this invoice due date calculator to turn an invoice date and payment terms into a clear due date. It supports common calendar-day terms and optional business-day counting for contracts that exclude weekends or bank holidays.

When to use it

Use this for quick payment planning and invoice admin. Contract wording can vary, so check whether your terms mean calendar days, working days, end of month, or another rule.

Payment terms in practice

Invoice terms vary more than the shorthand suggests. Net 7, 14, 30 and 60 are usually calendar days from the invoice date. "End of month" terms fall due at the end of the month of invoice, or the month after, depending on wording. "30 days end of month" combines both.

Because each of those produces a different date from the same invoice, the wording is the thing to read first — not the number.

Choosing calendar or business days

The calculator lets you count either way. Use calendar days for standard commercial terms, and business days where the contract explicitly says "working days" — the difference over a 30-day term is roughly eight calendar days.

Late payment and interest

UK business-to-business late payment rules allow statutory interest at 8% above base from the day after the due date, plus fixed compensation that scales with the debt. Consumer and non-commercial debts fall under different rules. Confirm both the due date and your status before charging interest.