Field help (VACBPR_SQH) 

The tax rule is used to define the various taxes that can be applied to the quote. Namely by cross reference with the tax levels of the products.

The tax rule is initialised with the customer tax regime. If this is a prospect, it is the tax ruleby default defined in the tax rule table that will be used. Once the quote is created, this information is no longer modifiable. If on the other hand the tax rule is modified after the entry of the quote lines but before creating the quote, the taxes will be recalculated for all the lines already entered.