Invoice Due Date Calculator

What Is the Invoice Due Date Calculator?

This tool calculates an invoice's due date by adding your payment terms (Net 7, Net 14, Net 30, Net 45, Net 60, or a custom number of days) to the invoice's issue date.

How to Use This Tool

Pick the invoice's issue date and choose a payment term from the dropdown (or choose Custom and enter the number of days). The due date appears instantly.

How the Date Is Calculated

The tool takes the invoice issue date and a number of days, and adds those days to the issue date on the calendar. The dropdown offers Net 7, Net 14, Net 30, Net 45, Net 60, and a Custom option that reveals a field where you type any number of days; the custom field starts at 30. The result is shown as a full date, such as a month, day, and year. The day count is rounded to a whole number, and negative values are treated as zero, in which case the due date equals the issue date. Nothing is shown until you pick an issue date.

A Worked Example

Suppose an invoice is issued on 20 January 2026 with Net 30 terms. Thirty calendar days later is 19 February 2026, so that is the due date. Because the calculation counts actual calendar days, it correctly handles months of different lengths and leap years. If the same invoice had Net 45 terms, the due date would fall in early March 2026, and the tool works this out without you needing to count days across months.

What the Tool Does Not Adjust For

• Weekends and holidays. If the computed date lands on a Saturday, Sunday, or a public holiday, the tool still shows that exact date. Whether a payment due on a non-business day is expected the previous or the next business day depends on your contract and the customer's practice, so state that in your terms.
• Terms that count from something other than the issue date. Some agreements count from delivery, receipt of goods, or the client's approval. In those cases, enter that date in place of the issue date.
• Terms such as end of month, often written EOM. Those add days to the end of the month rather than to the invoice date, so they cannot be reproduced by adding a plain number of days.
• Early-payment discount terms such as 2/10 net 30. This tool shows only the final due date, not the discount deadline, though you can run a second calculation with 10 custom days to find the discount cutoff.

Choosing Payment Terms

Shorter terms improve your cash flow but may be harder to negotiate with larger clients, who often have their own accounts-payable cycles. Many small businesses use Net 14 or Net 30; longer terms such as Net 60 are common with big organizations but can strain a small business that has to pay its own bills earlier. Put the due date itself on the invoice, not just the term name, so there is no ambiguity about when payment is expected. Include the invoice number and your payment instructions alongside it.

If you charge late fees or interest on overdue balances, make sure your written agreement states the rate and when it starts. Rules on what late charges are allowed vary by location, so check with a local authority or a legal professional instead of assuming a figure. Sending a polite reminder a few days before the due date often works better than waiting until the invoice is overdue.

Tips for Use

• Enter the date that will actually appear on the invoice, since a backdated or postdated issue date shifts the due date by the same amount.
• Use the Custom option for unusual terms such as 21 or 90 days.
• Pair this tool with the Client Invoice Number Generator on this site to set up a consistent, professional invoicing routine.

Frequently Asked Questions