SAP Message 5G158 - First two characters of the NINO are not valid

Diagnosis The R/3 system cannot locate the prefix (first two characters of theNational Insurance Number ) in the system table HR-GB NI Prefixes(T5G43). System Response This validation is necessary to ensure that your entered NationalInsurance Number conforms to the quality standards published by theInland Revenue. Procedure Please check this National Insurance Number again. If you determine theprefix is correct , raise a customer message with SAP Support.