Following the passage of the American Taxpayer Relief Act of 2012, the IRS issued Notice 1036 with respect to withholding tables for the year 2013, which includes the 2013 Percentage Method Tables for Income Tax Withholding.
Under the notice, the IRS requires the employers to implement the 2013 withholding tables as soon as possible, but not later than February 15, 2013. However, the use the 2012 withholding tables is permitted until employers implement the 2013 withholding tables; in such case, the employers should make an adjustment in a subsequent pay period to correct any under-withholding of social security tax by March 31, 2013.
One of the biggest news, of course, is the increase of the employee tax rate for social security to 6.2%. Previously, the employee tax rate for social security was 4.2%. The employer’s tax rate for social security remains unchanged at 6.2%. The social security wage base limit increases to $113,700. The Medicare tax rate is 1.45% each for the employee and employer, unchanged from 2012. There is no wage base limit for Medicare tax.
The second big news is that the withholding taxes will go up with Additional Medicare Tax for certain high-income wage earners. As described in an earlier article, starting January 1, 2013, Additional Hospital Insurance Tax (Additional Medicare Tax) of 0.9% will be imposed on employees who earn wages above certain thresholds. For the withholding purposes, the IRS requests that an additional 0.9% tax is withheld on wages paid to an employee in excess of $200,000 in a calendar year. The employer is required to begin withholding Additional Medicare Tax in the pay period in which he pays wages in excess of $200,000 to an employee and he should continue to withhold the Additional Medicare Tax each pay period until the end of the calendar year.
Note that Additional Medicare Tax is only imposed on the employee; there is no employer share of Additional Medicare Tax.