One: is my federal refund calculated only using the income tax withheld, and not the social security/medicare? Two: Why did OR refund decrease when I added another W-2?

[NewGuy · Accepted solution]

Social security and medicare taxes are totally independent of your federal taxes and are not subject to refunds unless you have overpaid them.

The refund meter shows your estimated return based on all the information you have entered up to that point.  When you enter one W-2, it calculates your taxes using all of your deductions and exemptions but only some of your income.  When you add more income via another W-2, your tax obligation will go up because you have no other deductions and credits to offset the additional income.  The refund meter will always be wrong until you enter all of your income and whatever deductions and credits to which you are entitled.