Del. Code tit. 9, § 8609

Upon the personal application of any taxable whose tax has been paid, a duplicate receipt shall be given for the applicant’s taxes upon its being shown that the receipt for such taxes has been lost, mislaid or destroyed, or in the possession of some person unknown to the applicant, or if known, who refuses to deliver the same; such receipt and its corresponding stub shall be plainly stamped with the word “duplicate.” This section shall not apply with respect to New Castle County.