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Net 30 Due Date Calculator

Enter an invoice date and payment terms — Net 15, 30, 45, 60, or custom — to get the exact due date, whether it's overdue, and the accrued late fee.

Invoice dateEvaluate as of

Payment terms

Optional: late-fee accrual

Invoice amount

Late fee rate (per month)

%/mo

Due date: 2026-10-26
Status: 30d left

How this is calculated

Payment terms are calendar days, not business days. The due date is the invoice date plus the term length; overdue status and late fees are measured against the date you're evaluating from.

1.Due date
invoice date + terms (days)
Net 30 from March 5 is April 4 — calendar days, including weekends and holidays.
2.Days until due / overdue
due date − as-of date
A positive number means days remaining; a negative number means days overdue.
3.Daily late-fee rate
(monthly rate % / 100) / 30
A simple, non-compounding daily rate derived from the stated monthly rate.
4.Accrued late fee
invoice amount × daily rate × days overdue
Only accrues once the invoice is actually overdue.

This is simple, non-compounding interest matching the standard 'X% per month' late-fee clause in most contracts. It does not check your state's usury cap — verify your rate is legally enforceable before invoicing a client.

How Net 30 payment terms work

“Net 30” is the most common payment term in B2B invoicing: it means full payment is due 30 calendar days after the invoice date, with no discount for early payment. The clock starts on the date printed on the invoice — not the date the client opens the email, and not the date work was completed — so keeping your issue date accurate matters more than it seems.

Net 15, Net 45, Net 60, and Net 90 all follow the identical rule with a different day count. Shorter terms (Net 15) are common for smaller invoices or newer client relationships where cash flow risk is higher; longer terms (Net 60, Net 90) are more typical with large enterprise clients whose accounts-payable cycles are slower, and are usually only worth offering if your own cash flow can absorb the wait.

Why the due date is easy to get wrong

Manually counting 30 days on a calendar is where most invoicing mistakes happen — month lengths vary from 28 to 31 days, and the math shifts every time the invoice date is near month-end. Invoice on January 31 with Net 30 terms and the due date is March 2, not March 1 or March 3 — a detail worth automating rather than counting by hand, especially when you're tracking due dates across a dozen open invoices.

Setting a late-fee clause that actually holds up

A late fee is only enforceable if it is written into the signed contract or invoice terms before the work begins — you cannot add one retroactively once an invoice is already overdue. The most common structure is a flat percentage per month (1% to 1.5% is typical), applied to the unpaid balance starting the day after the due date. Some states cap the maximum interest rate that can be charged without a written agreement (usury limits), so check your state's rules before setting a rate above roughly 1.5% per month.

Once the math is right, the fee still needs to appear on the invoice document itself to be enforceable — a calculator result alone doesn't constitute notice to the client. The Professional Invoice Template Pack includes a late-payment reminder template and an invoice format with a built-in payment-terms and late-fee field.

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Complete invoicing toolkit with tracker, payment receipts, and late-payment letters

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Related resources

Net 30 calculator FAQs

What does "Net 30" mean on an invoice?

"Net 30" means the full invoice amount is due 30 calendar days after the invoice date — not 30 business days, and not 30 days after the client received the goods or services. Net 15, Net 45, and Net 60 work the same way with a different day count.

How do I calculate a Net 30 due date?

Add 30 calendar days to the invoice date. If you invoice on March 5, the Net 30 due date is April 4. This calculator handles the month-length and leap-year math for you — just enter the invoice date and pick the term.

Is Net 30 the same as 30 days from receipt?

No, unless your contract specifically says "30 days from receipt of invoice." By default, "Net 30" is measured from the invoice date printed on the document, which is why the invoice date and issue date should always be the same day you send it.

How is a late fee calculated on an overdue Net 30 invoice?

Most contracts state a simple monthly rate (commonly 1–1.5% per month). This calculator converts that to a daily rate (monthly rate ÷ 30) and multiplies it by the invoice amount and the number of days overdue. Your contract or state law may cap the maximum allowable rate — check both before invoicing a client.

Can I use this for terms other than Net 30?

Yes. Pick Net 15, 45, or 60, or choose Custom to enter any number of days — Net 7, Net 10, and Net 90 all work the same way.

Does this calculator account for weekends or holidays?

No — Net terms are calendar days, not business days, unless your contract explicitly says "business days." If your contract uses business days, add extra days manually for any weekends or holidays in the period.