Field help (SSTOVRCD) 

Enter the code to use in order to override the default SST tax code from the product or invoice element. This tax code is recognized by Sage Sales Tax and is used to identify line types for tax purposes. This field is available only if the LTA - Local taxing activity code is activated, and the USATAX - Tax system user parameter is set to Yes.

For invoicing elements designated as the SST document discount for a company, you cannot remove the SST tax code value on the document.