The Validation Error normally come due to following reasons on GST Portal :-
1. Name and Date of Birth mismatch with PAN data base –
Taxpayer must verify the Name and Date of Birth related details submitted by him in Promoter /Partner and Auth. signatory tab. Put these details from taxpayers Income Tax Profile and not as printed on copy of PAN Card.
2. Name mismatch with UIDAI data base
Same as above, the name submitted in Promoter/Partner and Auth. signatory tab should match with AADHAR details provided by taxpayers.
3. In case of telephone/ office phone number/ Fax provided- STD code box should not be blank.
4. Use of duplicate mobile and email in the promoter tab and authorized signatory tabs using different records –
“ System error” occurred for non-core amendment
5. Check the registration details filled in the business details tab / particularly service tax registration number using special character.
6. Check that no tabs are left blank or mandatory fields left unfilled particularly in the principal place of business tab.
7. Also check HSN and SAC codes.