If a tax return and payment due date falls on a Saturday, Sunday, or a state or banking holiday, the return shall be postmarked on or before the fifteenth day of the second month succeeding the month for which the return and payment are due or received by the Department by midnight of the next business day the Department is open for business. This provision shall not apply to a return of the tax for the month of May.
A return and payment shall be deemed postmarked if it carries the official cancellation mark of the United States Postal Service or other postal or delivery services.
Va. Code § 58.1-2230