Once you are on the payroll, U.S. Citizens may change their tax withholdings online at the online payroll service center. If you have never used the system before, you need to know the agency code, which is 360222 and your last pay advice number. To access this number, you can look it up.
If you are not a U.S. Citizen, you must use a paper form. This form must be perfect, it cannot have any crossouts or errors. Please note that if you are on an F-1 or J-1 visa and not a resident alien for tax purposes (that is, you have been here less than five years), then you can only claim "0" or "1" in the Federal and State allowance boxes.If you have a fellowship during the current calendar year, you need to do two identical forms.
Maryland Taxes This is a link to Central Payroll for questions from U.S. Citizens regarding State of Maryland Taxes.