Under the compromise agreed to by President Obama and Senate Republicans, all the Bush tax cuts would be extended for 2011-2012, and all 2009 stimulus tax cuts except for the $400 "Making Work Pay" refundable credit, which would instead be replaced by a one-year cut in the social security payroll tax from 6.2% to 4.2% of wages. (This cut applies to the employee portion of the tax only - employers would still pay the full 6.2% for their portion of payroll taxes.)

Self employed persons using the calculator should note that it covers employee portion of the payroll tax only. Because they are responsible for both the employee and the employer portion, they should calculate their total payroll tax as 10.4% (6.2% + 4.2%) of their wages.