It's my first time paying AMT (due to receiving a chunk of backpay early in 2017).
I noticed that on the Tax Summary, turbotax has added "other taxes" of $156. After a LOT of searching, I found that most of this amount is equal to 0.9% x my income that is above $200,000.
This is the Additional Medicare Tax that applies to wages/income >$200K for single filer.
The problem is that my w2 form shows that my employer has already withheld the additional amount of medicare tax. My employer withheld 1.45%x$200,000 PLUS 2.35%x ($217,333-$200,000) or $3307, from my paychecks.
It looks like turbotax is making me pay the extra 0.9% TWICE!
If I already paid it (through withholding on my paychecks) why would I have to pay it again?
Is this an error in turbotax?
No, it is not. The implementation of Form 8959 is confusing. The amount of additional Medicare tax that is due is shown on Line 62 of Form 1040. However, the amount of additional Medicare tax that was withheld is included with normal wage withholding on Line 64 of Form 1040. In essence, Line 62 shows how much more you owe; Line 64 includes how much extra you paid.
Print Form 8959 to see how the reconciliation works (Part V). This has nothing to do with AMT.