How to restrict defaulting the Tax Rate for AP Transactions

Hi ,

As part of Regime to Rate Flow, I have made one Tax Rate Code as Default Tax Rate which is exclusively defined for Sales Transaction. Since it's made as Default Tax Rate, the same is defaulting to AP Invoices as well.

So I need to write an Exception Rule not to default, if it's blank Tax Line we are fine as Business users will manually select the required Tax based on the Transaction. Appreciate your inputs on this.