Problem in determining tax law (PT BR - direito fiscal)

Good Morning!

I have a problem in determining tax law (PT BR - direito fiscal) and I need help.

I created a new group on tax exemptions, which is filled with tax, base and tax law. When creating an order within the registered exception the rate and base are correct, however the tax law is not updated.

Do you have any idea what is causing this problem?

Or some documentation of how is determined in the tax law order?

Thanks,

Jisseléa de Carli