Select the Sales Tax check box if you want to change the Sales Tax field for work-in-process fee and cost transactions. The following options will then be available:

Old Maximum of 1 digit (0-9). Enter the Sales Tax Rate Code that you want to change or select it from the drop-down list. For example, if you want to change the Sales Tax Rate Code on transactions from 0 to 1, enter 0 in this field.
New Maximum of 1 digit (0-9). Enter the new Sales Tax Rate Code you want used on the transactions or select it from the drop-down list. For example, if you want to change the Sales Tax Rate Code on transactions from 0 to 1, enter 1 in this field.