Delaware Code
Subchapter II. Special Fuel
§ 5137. Refund of taxes erroneously or illegally collected.

In the event that any taxes, penalties or interest imposed by this law have been erroneously or illegally collected from a licensee, the Department of Transportation may permit such licensee to take credit against a subsequent tax report for the amount of the erroneous or illegal overpayment, or shall certify the amount thereof to the Secretary of Transportation who shall thereupon draw a warrant for such certified amount to such licensee. Such refund shall be paid to the licensee forthwith.
No refund of any taxes, fees, penalties or interest imposed under this chapter may be obtained except by filing a written claim with the Department before the expiration of 1 year from the earlier of:

(1) The date of the payment; or
(2) The date the payment was required to be made.
The claim must be in such form as may be prescribed by the Department, and shall specifically set forth the circumstances entitling the claimant to the refund.