Free Payment Terms Calculator

What are payment terms?

Payment terms define how long a client has to pay an invoice after it is issued. Net 30 means payment is due 30 days after the invoice date. Clear due dates reduce confusion and help you follow up on late payments.

How this calculator works

1. Enter the invoice date: Choose the date the invoice is issued or sent to the client.
2. Enter net days: Net days is the number of calendar days until payment is due, such as 7, 14, 30, or 60.
3. Add days to the invoice date: The due date is the invoice date plus the net days you entered.
4. See formatted dates: Results show both the ISO due date and a readable long-form date for your invoice or email.

Payment due date formula

Net days are added as calendar days to the invoice date. Net 30 on 15 January gives a due date of 14 February.

Worked example

You issue an invoice on 15 January 2026 with Net 30 terms. The due date is 15 January plus 30 days, which is 14 February 2026.

When to use this calculator

Use it when writing invoice terms, confirming a due date with a client, or checking when follow-up is appropriate on unpaid invoices.