CII-DT-097: Dates in the file must be written as eight digits (YYYYMMDD)

What it means

In a CII file every date sits in a DateTimeString element with a format attribute that says how the date is written. Format 102 means year, month and day as eight digits, YYYYMMDD. This covers dates such as the invoice date (BT-2), the due date (BT-9), the delivery date (BT-72) and the start and end of an invoicing period. The rule checks the shape of the text: a four-digit year, a month from 01 to 12 and a day from 01 to 31, with nothing else. Spaces around the digits are tolerated.

Why it matters

The recipient's software reads the date from those eight digits. A date written another way, such as with dashes, dots or a time of day, cannot be read reliably and could be misread. The file fails the check and the invoice is rejected.

How to fix it

Find the date that is flagged and rewrite it as year, month and day with nothing between them, for example 20261105 for 5 November 2026. Remove any dashes, dots, slashes, month names or time of day. In your invoicing software, check the date fields and the export or format settings, since the file is built from them. If you edit the XML, change the text inside DateTimeString so that it agrees with the format attribute.

The rule as published

Date time string with format attribute 102 shall be YYYYMMDD.

Where this rule applies