Calculation Methods for FUTA, Medicare, and Social Security

You can use these calculation methods for unemployment insurance (FUTA), Medicare, and Social Security (SS) taxes.

Calculation method	Run types	Self-adjustment method	What it does
Flat Rate	Regular and Supplemental	No Self Adjust	Withholding calculations don't self-adjust retroactively for any rate changes. If a back-dated rate change occurs, the payroll process uses the new rate only for the current run's taxable wages.
Flat Rate	Regular and Supplemental	Self Adjust	Bases the withholding calculations on year-to-date earnings, instead of earnings within a pay run. This provides the most accurate calculation. For retroactive rate changes, the payroll process self-adjusts the tax withholding or liabilities in the next available pay run.
Flat Rate	Regular and Supplemental	Self Adjust at Maximum	Similar to the Self Adjust method, except adjusts for changes only after the maximum annual taxable wage base is reached.