# XV-CZ-13

Source: https://xmlvalid.com/rules/XV-CZ-13

> …/UUID is the empty UUID (00000000-0000-0000-0000-000000000000); a UUID must be unique, or a second document with it is taken as a correction of the first (ISDOC 6.0.2, A.4).

- Level: error
- Rule sets: ISDOC amounts and identifiers Standard ISDOC 6.0.2
- Context: `isdoc:UUID`
- Test: `not(matches(normalize-space(.), '^[0\-]+$'))`

Validate a document against these rules: https://xmlvalid.com/validate