Section 7A. Any person engaged in the business of farming who shall buy any fuel on which an excise has been paid or is chargeable under this chapter and who, having consumed the same for farm purposes and is entitled to a refund of the federal gasoline tax paid on account of such fuel pursuant to section sixty-four hundred and twenty of the Federal Internal Revenue Code shall be reimbursed the amount of said excise in the manner and subject to the conditions herein provided. Claim for reimbursement of said excise with respect to fuel used during the taxable year for which such refund of the federal gasoline tax is due shall be filed on or before the fifteenth day of the fourth month following the close of such taxable year. Such claim shall be on a form prescribed by the commissioner. The commissioner shall transmit all claims approved by him to the comptroller for certification, and the amount approved by the commissioner and certified as aforesaid shall be paid forthwith from the proceeds of the excise tax levied under this chapter without specific appropriation.