I completed my 2017 1040 using Turbo Tax and everything flowed correctly to the 1040 including my withholding and tax calculation. Turbo Tax completed form 8959 correctly and the total additional Medicare tax flowed correctly to line 62 of my 1040. When I received my tax refund, my refund was reduced by the exact amount of the additional medicare tax. A later IRS notice indicated that my refund had been adjusted but gave no explanation. Any help or thoughts would be appreciated.
If you received a notice from the IRS regarding the adjusted refund, it should also list contact information for the agency that received the offset payment.
This article from the IRS says, "It will also include the agency that received the offset payment. It will also give the agency’s contact information."
If there's contact info on the letter you received, I'd recommend contacting the listed entity to inquire about the offset. TurboTax doesn't have access to see any of that information since it comes from the IRS.