how to add tax of 20% to sales

Fixing similar problems in my Org so stumbled on this. Thought I would provide my 2 cents to help anyone else still looking for these sort of things...

You would need to put a condition into the formula that applies if true (i.e. Categorise your products and add condition to check if they are a certain type such as camera or SaaS, or even simpler have a checkfield that you tick if tax should be applied: (note: take away my //comments on the formula)

If (

   ApplyTax__c = TRUE,   // determine if checkbox is ticked

   ($CurrencyField + ($CurrencyField * 0.20)), // if true, apply tax at 20%

   $CurrencyField  // else don't apply tax

)