PPC_ID_TAX is used to display the pay component where the amount of tax will be stored in. The tax is calculated during the U.S Legislation calculations by UPCALC or by a trial calculation.
UPCALC uses the pc usage to determine which PC Code to store the tax. For example, UPCALC knows that PC Usage 6621 is used for State Res Income tax and therefore will store the State Resident Income Tax in the Pay Component tied to the usage 6621.
