dmrktrading

toofun, I agree.
The calculation that makes most economic sense, and I have seen CFAI do it this way in places:
required return before tax% =[ (1 + required real return after tax%)*(1 + inflation%) - 1]/ (1 - tax%)
The same thing using additive method is:
required return before tax% = (required real return after tax% + inflation%) / (1 - tax%)