You filled out a form telling him how much to take out. The withholding is just an estimate. Your job doesn’t know what else will be on your tax return and how much the calculated tax will be and if you qualify for any credits, etc. Thats why you have to fill out a tax return to settle up with the state and see if you owe more or get a refund. You can give your employer a new form to have more taken out.
