How to enable Use Offset Taxes field at the Supplier Level

Hello Gurus,

I was wondering if you could tell me how to activate/enable (because presently it is grayed out - field is protected) the Use Offset Taxes field at the Supplier Level located on the Invoice Tax TAB.

It is presently enable at the site Level, but not at the supplier level.

I would like it enable at the supplier Level, plus I want it checked by default.

Let me know the steps or configuration setups required to acheive this action.

Thanks a lot

Regards

Philip