Fluctuations in SS and Med on employee paycheck

[Customer Service]

I have occasional fluctuations in Social Security and Medicare withholding on employee paychecks - Why?

Slight fluctuations are normal

A calculation change that was made in 2005 can make an employee's calculated SS and Medicare withholding fluctuate from period to period. The change is a self-adjusting mechanism in the program that uses an employee's year-to-date withholding up to the current paycheck and year-to-date wages-subject-to-SS or wages-subject-to-Medicare to calculate the current withholding so that the current year-to-date withholding is always as close to the IRS required percentages for SS and Medicare as possible. This typically affects only a few employees and even then is generally only a penny fluctuation.

Overrides and converted data may cause larger fluctuations

For example, you may override an employee's calculated value for SS or Medicare withholding in one payroll run so that it is considerably LESS than the IRS's required percentage of withholding. In the next payroll run, the employee's calculated value for SS or Medicare withholding will be considerably MORE than expected, as the self-adjusting mechanism brings the year-to-date withholding back into compliance with IRS requirements for SS or Medicare withholding.