Turn payment terms like Net 30 into an exact calendar date, and see how long is left before the invoice falls overdue.
2026-09-15 + 30 days = 2026-10-1530 days remain. Setting the due date in the invoice itself — not in a separate email — is what makes it enforceable if you ever have to chase.
Payment terms describe when an invoice must be paid, and the due date is that term expressed as a date on the calendar. "Net 30" means the full amount is due 30 days from the issue date. It is short for "net of any discount, payable in 30 days" — the phrase comes from the discount era, when Net 30 and 2/10 Net 30 meant different things.
The count starts from the issue date, not the date the client receives the email. That is why the issue date on the invoice matters: if it is left blank or backdated, the due date moves with it, and the client has a legitimate argument for paying later.
Calendar days and business days give different answers. Net 30 in calendar days is simply 30 days out. Net 30 in business days skips weekends, which stretches the deadline — common in construction and government work, where the term is written as working days.
Public holidays are the trap. A due date that lands on a bank holiday usually shifts to the next business day in practice, but the contract may not say so. When it matters, state the rule on the invoice or agree that the next working day applies.
From the invoice date, which is why that field must be filled in accurately. Some contracts specify receipt instead, but the invoice date is the standard basis and the one most bookkeeping systems assume.
The net amount is due 30 days after the invoice date, with no early-payment discount in play. Terms like 2/10 Net 30 add a discount: 2% off if paid within 10 days, otherwise the full amount in 30.
In most jurisdictions payment is expected the next business day, and many contracts state this explicitly. Add the rule to your terms to remove any ambiguity when a due date lands on a non-working day.
Shorter terms get you paid sooner but can push away larger clients with long approval cycles. Net 30 is the most widely accepted middle ground; Net 45 or 60 is more common with enterprise and government buyers.