Invoice Due Date Calculator
Calculate invoice due dates for Net 7, 15, 30, 45, 60, 90, and custom payment terms.
How is invoice due date calculator worked out?
An invoice due date is the invoice date plus the number of days in the payment terms. Net 30 means payment is due 30 calendar days after the invoice date, not 30 business days and not a calendar month.
Invoice Due Date Calculator
Payment due
30 September 2026
- Days to pay
- 30 days
- 30 calendar days after the invoice date
- Next business day
- 30 September 2026
- The due date is already a business day.
Show the working
| Invoice date | 31 August 2026 |
| Payment terms | 30 calendar days after the invoice date |
| Due date | 30 September 2026 |
Payment terms are shorthand, and shorthand gets misread. Writing the calculated due date on the invoice alongside the term removes the ambiguity entirely — customers act on dates, and "Net 30" requires the reader to do arithmetic they have no incentive to do accurately.
The formula
Due date = invoice date + net days (calendar days)
End of month = last calendar day of the invoice month
End of month + 30 = last day of the invoice month + 30 daysNet terms count calendar days including weekends and public holidays. If you need business days instead, say so explicitly on the invoice — it is not the default reading anywhere.
What Net 30 actually means
Net 30 means the full amount is due thirty calendar days after the invoice date. It is not thirty business days, it is not a calendar month, and it does not start when the customer opens the invoice or when the work was finished. Where a customer works to different assumptions — some accounts payable teams count from receipt, others from month end — the disagreement usually only surfaces when the invoice is already late, which is why the calculated date belongs on the document.
End-of-month terms and payment runs
End-of-month terms exist because many businesses pay in batches rather than continuously. If your customer runs a payment on the 25th, an invoice dated the 26th with Net 30 terms will not be paid in 30 days — it will miss that month's run and land in the next one, arriving nearer 50 days out. Asking when a customer's payment run happens, and dating invoices to arrive comfortably before it, is usually worth more than shortening your terms.
Shorter terms only work if you enforce them
Moving from Net 30 to Net 14 changes nothing on its own; what changes behaviour is following up the day after the due date, every time. Terms that are never enforced train customers to treat the due date as a suggestion, and once that expectation is set, shortening the term simply moves the date they ignore.
Frequently asked questions
How do you calculate an invoice due date?
Add the number of days in your payment terms to the invoice date, counting calendar days. An invoice dated 3 March with Net 30 terms is due on 2 April.
Does Net 30 mean business days or calendar days?
Calendar days, including weekends and public holidays. If you intend business days, you have to say so explicitly on the invoice, because it is not the standard reading.
What does 'due on receipt' mean?
That payment is expected immediately when the invoice arrives. It sets a clear expectation but is often impractical for business customers whose approval and payment cycles cannot move that quickly, so it works best for consumers and small jobs.
What happens if the due date falls on a weekend?
The due date stands, but payment will realistically arrive on the next business day since bank transfers do not usually settle at weekends. Some contracts state that a due date falling on a non-business day moves to the next one — worth writing into your terms if the timing matters.
Put the number on an invoice
The free invoice generator builds the document around your figures — line items, tax, payment terms — and downloads a print-ready PDF. No signup required.
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