Employers are required to withhold an additional 0.9% of income for Medicare once your wage income exceeds $200,000 for the year. Form 8959 is used to reconcile the additional Medicare tax withheld with the actual additional Medicare tax owed. The additional amount you owe is shown on Line 62 of Form 1040 (along with amounts from Form 8960, for example), and the additional amounts you paid in are included on Line 64 as withholding.
