Hi there, duhpensacola.

Incorrect calculation for Medicare or Social Security is usually caused by discrepancies in previous transactions. For example, an older paycheck has an over or under calculation when it was created. This would result the program to auto correct since the year-to-date amount is not exactly 6.2% for Social Security and 1.45% for Medicare.

You can the Payroll Detail Review report as suggested in the previous replies. Then, make sure to use This Calendar Year in the the Dates field to get the total amount for the year. 

You might also need to create a liability adjustment or let QuickBooks auto correct until the year-to-date amount is right amount. Here's an article for more details: Adjust Payroll Liabilities In QuickBooks Desktop.

Please don't hesitate to reply below if you need anything else.