Invoice Due Date Calculator

How to use the due date calculator

1. Pick "Due date from a term", or "Days between two dates" to compare an invoice date with a payment date.
2. Enter the invoice date, or the date your terms count from.
3. Choose the payment term: Net 0 to Net 90, a custom number of days, EOM, prox or 2/10 Net 30.
4. Choose what happens when the due date falls on a Saturday or Sunday.
5. Press Calculate due date, then copy the result onto the invoice.

What is an invoice due date?

The invoice due date is the date by which the customer must pay the invoice in full. It follows from two things printed on the invoice: the invoice date and the payment term. On Net 30, for example, the due date is the invoice date plus 30 calendar days. The due date printed on the invoice is the last day for on-time payment unless the contract says otherwise.

• Print the date, not only the term. Write "Net 30 — due 2 Mar 2026" (for an invoice dated 31 Jan 2026) rather than "Net 30" alone, so nobody has to count days and both sides work from the same date.
• Due date vs payment date. The due date is the deadline; the payment date is the day the money is actually paid. The difference between them is how early or late the payment was, and the "Days between two dates" mode above works it out.
• Start date. "Net N" on an invoice normally counts from the invoice date. If your contract counts from another event, such as receipt of the invoice, delivery or completion of the work, enter that date instead.

For the amounts that go on the invoice, use the invoice calculator. The glossary defines the maturity date and the amount due.

How the due date is calculated (with examples)

Net N: due date = invoice date + N calendar days. Weekends and public holidays are counted.

• Net 30 on an invoice dated 31 Jan 2026 → 2 Mar 2026 (Monday). February 2026 has 28 days, so the date lands in March.

N days EOM (end of month): the count starts from the last day of the invoice month: due date = last day of invoice month + N days (method 1). A second reading counts N days from the invoice date and then runs to the end of that month (method 2).

A French ministerial answer on "45 jours fin de mois" (45 days end of month) describes both readings: "Le mode de computation du délai de 45 jours fin de mois n'est pas imposé par la loi" (the law does not impose a counting method). The calculator shows method 2 whenever it gives a different date: agree the method with your customer and print the date on the invoice.

• 30 days EOM on an invoice dated 10 Feb 2026 → 30 Mar 2026 (method 1: 28 Feb 2026 + 30 days). Method 2 gives 31 Mar 2026.
• Net 10 EOM on an invoice dated 20 Mar 2026 → 10 Apr 2026 (method 1: 31 Mar 2026 + 10 days). Method 2 gives 31 Mar 2026.
• 45 days EOM on an invoice dated 15 Jan 2026 → 17 Mar 2026 under method 1, or 31 Mar 2026 under method 2.

Prox (day D of next month): due on day D of the month after the invoice month, e.g. "10th prox" on an invoice dated 20 Mar 2026 → 10 Apr 2026.

In a spreadsheet (invoice date in cell A2):

• Net 30: =A2+30. Microsoft's Excel help: "You can enter a negative number to subtract days from your start date, and a positive number to add to your date."
• 30 days EOM, method 1: =EOMONTH(A2,0)+30. Method 2: =EOMONTH(A2+30,0). EOMONTH "Returns the serial number for the last day of the month that is the indicated number of months before or after start_date" (Excel); Google Sheets uses the same syntax, EOMONTH(start_date, months). Format the cell as a date.

Sources: Microsoft Support, EOMONTH function and Add or subtract dates; Google Docs Editors Help, EOMONTH; Assemblée nationale written answer 14-63277QE (JO 6 Oct 2015) on the two ways to count "45 jours fin de mois". Checked 25 Sep 2026.

Due dates by payment term

For an invoice dated 15 Jan 2026. Each Net term links to its own page with a calculator locked to that term, a month-by-month table and wording to copy; each EOM term links to a guide that shows both counting methods and the wording.

What "EOM" means and how the two methods differ: EOM payment terms explained. Every other term, the legal payment periods and wording examples: invoice payment terms guide. For recurring invoices, the billing cycle calculator lists the dates of each cycle. Ready-made layout: the Net 30 invoice template. VAT return and payment dates are a different calculation: see the VAT deadline calculator.