CII-SR-400: Write the due date as a date string, not a date-time

What it means

The due date (BT-9) inside the payment terms is written with a DateTime element. EN 16931 expects the due date in a DateTimeString element with format 102, which is the date as eight digits in the order year, month, day.

Why it matters

This is a warning, so the invoice is still accepted. But a system that reads the due date only from DateTimeString will not find it, and may treat the invoice as having no due date. It is worth fixing because the due date tells the buyer when to pay.

How to fix it

Replace the DateTime element inside the due date with a DateTimeString element, add the attribute format with the value 102, and write the date as eight digits. Most invoicing software writes this for you, so if you cannot edit the file, look for an export setting or an update that produces EN 16931 dates, or ask the vendor.

The rule as published

DateTime should not be present

Where this rule applies