Yes, it is quite common for this to happen for a number of reasons. You pay taxes on your total income, not based on each W2 entry. The first cause is due to the way the standard deduction and personal exemption works in our taxing system. If you are single, then the first $10,350 of your income is not taxed because of standard deduction ($6,300) and your personal exemption ($4,050). And these amounts are more if your are married filing jointly or head of household or have dependent exemptions.