BR-GA-7
There MUST be a Payment Means identifier (NL-GA-04) with a value equal to 'GACCOUNT'
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
/ubl:Invoice
Test
count(cac:PaymentMeans/cbc:ID[text()='GACCOUNT']) = 1
Checked with Netherlands SI-UBL 2.0 G-account Invoice