Payment due for vehicles purchased or moved into the county and registered with Fairfax County on or after July 1 of the prior year. Learn about filing deadlines and payment due dates for various county tax types.Tax bills are mailed approximately 30 days before the due date. Please have your account number and payment amount ready. Payment must be received in our office at least one day prior to your court date. You may not prepay the fine and costs if your charge is for reckless driving. Our new online Customer Portal allows you a new way to view and pay your bills. Fill out the intake form and have your login credentials sent directly to your inbox.