https://userapps.support.sap.com/sap/support/knowledge/en/3391943
3391943 - Tax number of tax category saved in TAXNUMXL instead of TAXNUM in table DFKKBPTAXNUM |...
When saving tax number of tax category in BP, it is saved in 'TAXNUMXL' instead of 'TAXNUM' in table DFKKBPTAXNUM.