Ok I explain better. VAT and other taxes are not calculated or are calculated on percentage or their amount about particular items, so you should add the feature to let set the percentage to apply on their amount about VAT and/or local tax during product creation, for example 50% about VAT and 100% about local tax; or 0% about VAT (so don't calculate VAT in this case) and 100% about local tax (calculate fully in this case). If you allow to set this during product creation, user can preset this calculation and once he add on the invoice it's done already. Obviously let edit this calculation on the invoice always.
I hope it's clearer now.

Hello Francesco,

I understand it, but we need to consider if this is a feature that would be useful for most users.

However, if you really need it, it could be made through custom coding.

Regards,
Joan

At least add the feature to apply or not VAT and or local tax to product. In my country sometimes the taxes don't consider the amount of expenses.

Please consider that usually the taxes don't consider the amounty of expenses because they are taxed already when you pay them.