Verkkotax due dates and deadlines. Sign up for tax reminders on fairfax alerts. For all due dates, if the date falls on a saturday, sunday, or county holiday, the due date is. Verkkothe department of tax administration (dta) reviews the assessed values for all real property each year with january 1 as the effective date. In accordance with the. (dc news now) — homeowners in fairfax county will see a 7% increase in taxes this year, thanks to higher home valuations. Verkkowelcome to fairfax county's real estate assessment site. This site provides assessed values and physical characteristics for all residential and.