Invoice due date calculator
Enter the invoice date and the payment term you agreed with your customer. You will see the due date, the weekday and how many days are left or overdue.
- Invoice date
- Friday 6 November 2026
- Days since the invoice
- 55
- Status today
- 55 days left
How it was calculated
- Due date = Friday 6 November 2026 + 30 days = Thursday 31 December 2026
- With month-end payment the due date moves to the last day of the month: Thursday 31 December 2026.
The term is whatever you agree with your customer; ask your advisor about the limits set by late-payment rules.
Indicative result: it does not replace an advisor's advice.
Keep track of which invoices are due and whom to chase
Collections flags what is pending and overdue so none slips through.
See Collections Create a free accountHow is an invoice's due date calculated?
You add the payment term to the invoice date. With an invoice dated 6 November and a 30-day term, it falls due on 6 December. If the term is agreed “at month end”, the due date moves to the last day of that month.
What payment term should I put on my invoices?
The one you and your customer agree in writing: 15, 30 or 60 days are common. Always state it on the invoice or quote, together with the payment method. Late-payment rules limit maximum terms: confirm them with your advisor.
What do I do when an invoice falls due and is not paid?
First a friendly reminder; then a formal written claim. You can prepare the letter with the unpaid-invoice letter tool and keep track of what is pending in Collections.
Worked example
An invoice dated 6 November 2026 with a 30-day term falls due on Sunday 6 December 2026. With month-end payment, the due date moves to 31 December 2026.
How to use this tool
- Enter the invoice date.
- Enter the agreed payment term in days (and whether it is month end).
- Read the due date and the days left.
Frequently asked questions
How do I work out when an invoice is due?
Add the term in days to the invoice date. This tool does it for you and tells you how many days are left.
What does “payable at month end” mean?
The due date moves to the last day of the month in which the term ends.
Is a due date on a holiday pushed back?
This tool does not adjust it: it shows the weekday so you can take it into account.
What maximum payment term can I agree?
Late-payment rules set limits; ask your advisor before agreeing long terms.
Keep reading
- Free invoicing software in Spain: what to look for
- Invoicing foreign clients from Spain
- Unpaid invoice reminder letter
- Spanish VAT calculator
- VAT and IRPF withholding calculator for invoices
- Free invoice generator
- All free tools
Reviewed on 6 November 2026. Indicative result: it does not replace an advisor's advice.
Never miss an invoice due date
Collections tracks due dates and reminders.
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