Section 33. Any vendor who has paid to the commissioner an excise under this chapter upon a sale for which credit is given to the purchaser and such account is later determined to be worthless shall be entitled to reimbursement without interest of the excise paid to the commissioner on such worthless account. Such claim for reimbursement, covering the amount of excise paid on accounts determined to be worthless in the vendor's prior fiscal year, shall be filed on or before the due date, including extensions, of the federal income tax return (or annual federal filing in the case of an exempt organization) for such prior fiscal year. Any vendor who shall recover, in whole or in part, upon an account previously determined to be worthless for which reimbursement had been received, shall report and include the same in his return for the period during which the recovery occurred. For the purposes of this section, a vendor shall include a person who has made a prepayment of tax under section 3A.