Due to components coming from different suppliers not ever product will have the same rate pending on where you buy or sell to.
BUZ has the ability to have several tax rates that you can apply to products.
To create a Tax rate follow the steps below.
Settings → 
→
Description: The BUZ descriptive name.
Code: Description abbreviation, maximum of 10 characters.
Tax Percentage: This is the percentage to be applied to/ already included in the net price.
A positive 
percentage means the tax need to be added to the price quoted.
A negative 
percentage means the tax is already included in the price and for sales reporting needs to be deducted from the sales value. The maths also means a 10% tax included is deducted using 10/(100+10) or 1/11th.
It may help to know that internally in BUZ, Sales is recorded excluding tax and the Tax is recorded separately.
For examples on the Tax Rate Calculations Tax example