Field help (PPCCNVFLG) 

The Ex-Tax/Inc Taxfield is used to define whether the price in the price list records entered with this setup will be ex-tax or tax incl.
When entering the order or, in general, in the purchasing cycle, the unitary price is automatically expressed ex tax. The tax inc price entered on the price list records will be automatically converted into ex tax in journal entry.
SEEINFO This conversion field cannot be accessed.