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Invoice Due Date Calculator

Enter your invoice date and payment terms to find the due date.

Payment due date

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What this calculator does

This online calculator adds your payment terms (Net 15, 30, 45, 60, 90, or a custom period) to your invoice date to find the exact payment due date, plus how many days remain or how overdue it is.

Worked example

An invoice dated August 3, 2026 with Net 30 terms is due onSeptember 2, 2026.

Common mistakes

  • Confusing the invoice date with the delivery or service date. Payment terms are almost always calculated from the invoice date itself, not when goods or services were delivered.
  • Assuming "Net 30" means 30 business days. Unless explicitly stated otherwise, Net terms use calendar days, not business days.
  • Missing early payment discount windows. Some invoices offer a discount for paying well before the due date (e.g., "2/10 Net 30") — check the fine print separately from the due date itself.

Frequently asked questions

What does 'Net 30' mean?+

Net 30 means payment is due within 30 days of the invoice date. Net 15, Net 45, Net 60, and Net 90 follow the same pattern with a different number of days.

Does the invoice date count as day zero or day one?+

This calculator treats the invoice date as day zero and adds the full payment term to it, which is the standard convention for Net terms — for example, Net 30 from January 1 is due January 31.

What if my payment terms aren't a standard Net period?+

Use the custom days field to enter any specific number of days from your contract or agreement.

Is there a grace period after the due date?+

That depends entirely on the agreement between the parties — some contracts specify late fees starting immediately after the due date, others allow a short grace period. Check your specific invoice terms.

How do you calculate a Net 30 due date?+

Add 30 calendar days to the invoice date. This calculator does the addition for you for Net 15, 30, 45, 60, 90, or any custom term, and also shows how many days remain until it's due.

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