Many taxpayers are affected by the new additional Medicare tax that became effective beginning January 1, 2013. As an employer and as a self-employed taxpayer, you need to know how this new tax affects employees and the self-employed.

The Tax Relief for Americans Act of 2013, signed into law on January 2, 2013, included a provision to increase the employee portion (Medicare taxes for higher-income individuals (both employees and self-employed business owners).

The additional tax rate is 0.9% on employee income (employers do not have to contribute to this additional tax). The additional Medicare tax is effective for income over a specific level, depending on the individual's federal income tax filing status.

The additional Medicare tax rate of 0.9% is applied to combined employment income and self-employment income above these levels:

• Married filing jointly - $250,000
• Married filing separately - $125,000
• Single - $200,000
• Head of household (with qualifying person) - $200,000
• Qualifying widow(er) with dependent child - $200,000

Read more about the Additional Medicare Tax and Payroll Accounting.

Detailed explanations of how the Additional Medicare Tax works in specific situations:

William Perez (at Tax Planning) has an excellent series of articles about this additional tax that high-earning employees and self-employed individuals must pay. Each article takes the reader through the process of completing Form 8959 (currently in draft form PDF from the IRS).

 

• For single individuals
• For a married couple who don't owe Medicare tax but have it withheld
• For a married couple who owe the additional Medicare tax but didn't have it withheld
• For self-employed business owners

Why employers need to know how the additional Medicare tax works:

So, why should you, as an employer, want to read his detailed explanations of how the new Medicare tax works for single individuals and married couples?

1. Employees ask questions. Employers are required to withhold additional Medicare tax, above the 1.45% Medicare tax rate, at a rate of 0.9% on Medicare wages in excess of $200,000 paid to an employee. The amount of Medicare withholding may not be the amount an individual must pay, and the employee may be confused about how the withholding works. Some employees may have additional Medicare tax due in excess of the amount withheld. This additional tax must be paid on the individual's personal income tax return.

While employers cannot give tax advice, they need to know the possible differences between amounts withheld and amounts payable by employees. TheIRS says:

...an employee who anticipates liability for Additional Medicare Tax may request that his or her employer withhold an additional amount of income tax withholding on Form W-4. This additional income tax withholding will be applied against all taxes shown on the individual’s income tax return (Form 1040), including any Additional Medicare Tax liability.

2. It's on the W-2 you send to employees. When you send W-2 forms to employees in January, you should include an explanation of line 5 "Medicare wages and tips." Employees who had the additional Medicare tax withheld may have questions about this form and the difference between Medicare wages on this line and the amount withheld for Medicare tax withheld on Line 6.

For example, if you as an employer withheld the additional Medicare tax above $200,000, and the employee is married, filing jointly, the employee doesn't have to pay the additional Medicare tax until his/her income exceeds $250,000. In this case, the amounts in Line 5 and Line 6 will be different, and the employee may be entitled to a refund of some or all of the amount withheld.

3. You may be an employee. If you work as an employee with another business other than your own, or if you are an employee of your corporation or S corporation, you will need to know how this Medicare tax works as you receive your own W-2 form. If you have earned more than the amounts listed above, you may have to make your own decisions about paying for additional amounts of Medicare tax or getting a refund for Medicare tax.

4. You may be self-employed as a business owner. The new Medicare tax also affects self-employed individuals who earn over a specific amount. If you are both an employee and self-employed, all sources of earned income (as opposed to investment income) are combined to reach the levels (above) where the additional Medicare tax is applicable. There is no withholding for self-employment tax, and you expect that your income might be above the levels above, you will need to increase the amount of your estimated tax payments to account for the additional Medicare tax.

You can find more detailed information on the specifics of the Additional Medicare Tax, from the IRS.