I paid the 4th qtr Medicare premium on 1/2/18. Can I deduct 4 quarters in 2017 or must I deduct 3 in 2017 & 5 in 2018?

3 in 2017, and 5 in 2018 (assuming you pay all of the 2018 quarters in 2018).

thanks, but how do you know this? are you a tax expert?

thanks SweetieJean, I just learned that I could click on your name & see your background....so thanks again