ToolSahla, Tools Sahla

Why do I get an error when I enter the invoice due date?

Because the due date you picked falls before the invoice date, which the tool does not accept; it shows 'This date cannot be earlier than the document date'. Either correct one of the two dates or leave the due date empty, since it is optional anyway.

Published · 2 min read

Why the rule exists

The due date is the last day payment is expected. An invoice issued on 20 September asking to be paid by 10 September asks for the impossible, and a client reading it cannot tell which date is the mistake. So the Basic invoice generator checks this before building the file and will not create a PDF until it is fixed.

A due date on the same day as the invoice is fine, and suits an invoice payable on receipt.

The causes we see most

  • You changed the invoice date after setting the due date: you picked 30 September as due, then dated the invoice 5 October because delivery slipped, and now the due date comes first.
  • You typed the date by hand and misread the day and month order: some browsers show the month first, so 09/10 is the tenth of September, not the ninth of October.
  • The year is wrong, 2025 instead of 2026, which happens a lot in the first days of a new year.
  • You copied the due date from an old invoice and forgot to update it.

Fixing it quickly

  1. Look at the invoice date first and make sure it is really the date you want.
  2. Open the date picker in the due date field and choose the day from the calendar instead of typing, which removes any day-month confusion.
  3. If there is no fixed deadline, clear the due date and put the terms in the payment details, such as 'Payable on receipt'.
  4. Create the PDF again and check both dates in the header of the preview.

What about invoices with an earlier date?

Sometimes you issue an invoice today for work finished last month. The tool does not block an older invoice date; it only requires the due date to be on or after it. Whether backdating is acceptable in your business is an accounting matter for your accountant, not the tool. It is usually clearer to date the invoice on the day you issue it and name the period in the line description, such as 'Services for August'.

And if the client has already paid and nothing is outstanding, what you need may be a receipt from the Receipt generator rather than an invoice with a due date.