XV-MY-26
Each line needs the description of the product or service (cac:Item/cbc:Description), up to 300 characters; line … has none or a longer one.
error: the document is invalid
What the rule checks
As the rule set's publisher wrote it. The rule runs on every element the context matches, and fails where the test is false; the validator reports the line of that element.
Context
/*/cac:InvoiceLine
Test
$description ne '' and string-length($description) le 300
Checked with MyInvois e-Invoice