With department approval, the owner of a nonfleet vehicle may change the vehicle's registration expiration date. The owner will be assessed RTA excise tax based on the current depreciation rate for the number of months from the current expiration to the requested expiration date. The new expiration date must be greater than twelve months but not more than eighteen months from the current registration expiration date. New expiration dates may only be granted when validation tabs for the desired month and year are available.