The Tax Type and Tax Code fields are used by the Tax Rate Determination (TRD) system for automated sales tax processing and each invoice line item must contain a valid tax type and tax code for proper operation of this system. If these fields are missing, they must be filled in with the appropriate information before sales may be posted. Please see the Tax Rate Determination (Sales Tax Processing) documentation for a complete description of the TRD system and the valid entries for these fields.