You wouldn't need to enter a refunded amount to Medicare Part B, since they simply refunded an amount you overpaid.
But tax withheld? I don't understand. Did you receive a tax document reporting the refund and tax withheld?
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
