https://userapps.support.sap.com/sap/support/knowledge/en/2174505
2174505 - KBA: NL: Incompleteness error message: /SAPSLL/CUS_ECC538 Document number not allowed;...
Incompleteness error message: /SAPSLL/CUS_ECC538 Document number not allowed; see long text Incompletion check for NL issues message "Document number not...