(a) Requirement
Except as provided in subsection (b) and notwithstanding any other provision of this chapter, no mortgage covering new or rehabilitated multifamily housing or a property or project described in subchapter IX–B shall be insured under this chapter unless the mortgagor has agreed (A) to certify, upon completion of the physical improvements on the mortgaged property or project and prior to final endorsement of the mortgage, either (i) that the approved percentage of actual cost (as those terms are herein defined) equaled or exceeded the proceeds of the mortgage loan or (ii) the amount by which the proceeds of the mortgage loan exceeded such approved percentage of actual cost, as the case may be, and (B) to pay forthwith to the mortgagee, for application to the reduction of the principal obligation of such mortgage, the amount, if any, certified to be in excess of such approved percentage of actual cost. Upon the Secretary's approval of the mortgagor's certification as required hereunder, such certification shall be final and incontestable, except for fraud or material misrepresentation on the part of the mortgagor.

(b) Exemption for certain projects assisted with low-income housing tax credit
In the case of any mortgage insured under any provision of this subchapter that is executed in connection with the construction, rehabilitation, purchase, or refinancing of a multifamily housing project for which equity ¹ provided through any low-income housing tax credit pursuant to section 42 of title 26, if the Secretary determines at the time of issuance of the firm commitment for insurance that the ratio of the loan proceeds to the actual cost of the project is less than 80 percent, subsection (a) of this section shall not apply.

(c) Definitions
For purposes of this section, the following definitions shall apply:

(1) The term "new or rehabilitated multifamily housing" means a project or property approved for mortgage insurance prior to the construction or the repair and rehabilitation involved and covered by a mortgage insured or to be insured (i) under section 1713 of this title, (ii) under section 1715e of this title with respect to any property or project of a corporation or trust of the character described in paragraph (1) of subsection (a) of section 1715e of this title or with respect to any property or project of a mortgagor of the character described in paragraph (3) of subsection (a) thereof, (iii) under section 1715k of this title if the mortgage meets the requirements of paragraph (3)(B) of subsection (d) thereof, (iv) under section 1715l of this title if the mortgage meets the requirements of paragraph (3) or paragraph (4) of subsection (d) thereof, (v) under section 1715v of this title, (vi) under section 1715x of this title if the mortgage meets the requirements of subsection (b), (vii) under section 1748h–2 of this title if the mortgage meets the requirements of subsection (f), (viii) under section 1715y(d) of this title, or (ix) under section 1715z–1 of this title;

(2) The term "approved percentage" means the percentage figure which, under applicable provisions of this chapter, the Secretary is authorized to apply to his estimate of value, cost, or replacement costs, as the case may be, of the property or project in determining the maximum insurable mortgage amount; except that if the mortgage is to assist the financing of repair or rehabilitation and no part of the proceeds will be used to finance the purchase of the land or structure involved, the approved percentage shall be 100 per centum; and

(3) The term "actual cost" has the following meaning: (i) in case the mortgage is to assist the financing of new construction, the term means the actual cost to the mortgagor of such construction, including amounts paid for labor, materials, construction contracts, off-site public utilities, streets, organizational and legal expenses, such allocations of general overhead items as are acceptable to the Secretary, and other items of expense approved by the Secretary, plus (I) a reasonable allowance for builder's profit if the mortgagor is also the builder as defined by the Secretary, and (II) an amount equal to the Secretary's estimate of the fair market value of any land (prior to the construction of the improvements built as a part of the project) in the property or project owned by the mortgagor in fee (or, in case the land in the property or project is held by the mortgagor under a leasehold or other interest less than a fee, such amount as the mortgagor paid for the acquisition of such leasehold or other interest but, in no event, in excess of the fair market value of such leasehold or other interest exclusive of the proposed improvements), but excluding the amount of any kickbacks, rebates, or trade discounts received in connection with the construction of the improvements, or (ii) in case the mortgage is to assist the financing of repair or rehabilitation the term means the actual cost to the mortgagor of such repair or rehabilitation, including the amounts paid for labor, materials, construction contracts, off-site public utilities, streets, organization and legal expenses, such allocations of general overhead items as are acceptable to the Secretary, and other items of expense approved by the Secretary, plus (I) a reasonable allowance for builder's profit if the mortgagor is also the builder as defined by the Secretary, and (II) an additional amount equal to (A) in case the land and improvements are to be acquired by the mortgagor and the purchase price thereof is to be financed with part of the proceeds of the mortgage, the purchase price of such land and improvements prior to such repair or rehabilitation, or (B) in case the land and improvements are owned by the mortgagor subject to an outstanding indebtedness to be refinanced with part of the proceeds of the mortgage, the amount of such outstanding indebtedness secured by such land and improvements, but excluding (for the purposes of this clause (ii)) the amount of any kickbacks, rebates, or trade discounts received in connection with the construction of the improvements: Provided, That such additional amount under (A) of this clause (ii) shall in no event exceed the Secretary's estimate of the fair market value of such land and improvements prior to such repair or rehabilitation, and such additional amount under (B) of this clause (ii) shall in no event exceed the approved percentage of the Secretary's estimate of the fair market value of such land and improvements prior to such repair or rehabilitation. In the case of a mortgage insured under section 1715k, 1715l(d)(3), 1715l(d)(4), 1715v, 1715x, or 1715z–1 of this title where the mortgagor is also the builder as defined by the Secretary, there shall be included in the actual cost, in lieu of the allowance for builder's profit under clause (i) or (ii) of the preceding sentence, an allowance for builder's and sponsor's profit and risk of 10 per centum (unless the Secretary, after finding that such allowance is unreasonable, shall by regulation prescribe a lesser percentage) of all other items entering into the term "actual cost" except land or amounts paid for a leasehold and amounts included under either (A) or (B) of clause (ii) of the preceding sentence. In the case of a mortgage insured under section 1715k, 1715l(d)(3), 1715l(d)(4), 1715v, 1715x, or 1715z–1 of this title, where the mortgagor is not also the builder as defined by the Secretary, there shall be included in the actual cost an allowance for sponsor's profit and risk of the said 10 per centum or lesser percentage of all other items entering into the term "actual cost" except land or amounts paid for a leasehold, amounts included under either (A) or (B) of the said clause (ii), and amounts paid by the mortgagor under a general construction contract.