AKelly, I don't see how you could be amending with TurboTax online since that option is no longer available. Perhaps you meant to say that are using the TurboTax amendment software installed on a PC or Mac for amending a tax return originally filed using TurboTax online.
I'm not aware of any situations where TurboTax miscalculates the taxable amount of Social Security benefits when correct entries are made into TurboTax. As far as I known TurboTax faithfully implements Worksheet 1 of IRS Pub 915. Any miscalculation of Social Security benefits by TurboTax generally means an entry error of some portion of income or above the line deductions.
