There are dozens of sets of modifications to AGI for different purposes. I think only one of them, if any, adds back the deductible portion of self-employment taxes, and it's not the MAGI for the purpose of a Roth IRA contribution. People have been complaining about that terribly misleading TurboTax advice page for years yet no meaningful changes have been made to it. That TurboTax advice page should be ignored.
