Work out an invoice due date

Net 30 from the 14th, or end of next month + 5 — payment terms are date math with conventions attached.

Tools used in this guide

The job

Invoices say "net 30" or "end of month plus 20 days" — the client wants a calendar date, and weekends complicate whether that date is real.

Compute it

Set the invoice date, choose the terms — net N days, end of month +N, or end of next month +N — and pick whether a weekend due date rolls forward or back. The result shows the date, its weekday, and days from today.

End-of-month conventions matter in Japan: 締め日 billing often means "end of next month + N".
Weekend adjustment is a shift, not business-day arithmetic — holidays aren't modelled.

Worked example

Invoice dated 14 March, end-of-next-month + 20: the due date lands on 20 May. If that's a Sunday and adjustment is forward, payment is due Monday 21 May.

Limits

Calendar-day math between 1900 and 2100, independent of time zones and daylight saving. Public holidays aren't included — check the company's calendar separately if the date must be a business day.