Tax codes are used for invoicing, purchase order, sales order and sales quotation in FSM.
The base setting for this must be done in "/PACG/ECM_NOAS - No Object Assignment" with object ID "TAXCODE" for the company.
Below is the at press time current FSM DTO versions. 
Newly created and changes in /PACG/ECM_ATAXC will not be updated automatically in FSM. Please use /PACG/ECM_TRIG_TAXC - Tax code to manually sent it from SAP ERP to FSM.
The below example shows the tax code sent over to 