Return Calcs for Portfolio Management framework, different, solution, example, outside

cfa10yrplan

It has become apparent to me that the order in which the return components are taken into consideration effects the solution calculated under both the (1+r)(1+i)-1 framework, and the r+i framework. For example, first, adding inflation/fees (either additively or multiplicatively), then grossing the return up for taxes, or conversely, gross up the return for taxes, then adding inflation/fees (either additively or multiplicatively), yield very different solutions that are outside of what would be called a rounding error.

Is one methodology more correct than the other?

The Q1 on the 2009 exam grosses the return up for taxes, and then adds inflation, however, most of the solutions to Schweser study problems adjust for inflation/fees first.

Any insight is appreciated. Thanks and good luck.