Va. Code Ann. § 58.1-477

The Tax Commissioner may grant an employer a reasonable extension of time for filing any return under this article whenever in his judgment good cause exists. Whenever under the terms of such an extension the payment of any amount or amounts of money to the Tax Commissioner by the employer is postponed for a longer period than ten days from the time the same would be otherwise due and payable, such employer shall be charged with interest on such amount or amounts at a rate determined in accordance with § 58.1-15, from the time such amount or amounts were originally due and payable to the date of payment under the terms of the extension.