R12: Can we enter WHT (withholding Tax) and VAT at the invoice distributions rather than Invlice lin

We want ti simplify the invoice entry process for training the end users. In R12 since for every invoice header there must be one invoice line. So we will enter basic information in invoice lines the basic information  (amount,description , type) and proceed to enter the remaing details (accounting, project ,tax etc..)  details in distributions.

However at the distribution lines we see the WHT & tax code are disabled ,can you please tell us is there any set-up missing.

regards