(a) The term "insurance corporation" includes a corporation, association, joint stock company or association, person, society, aggregation or partnership, by whatever name known, doing an insurance business, and, notwithstanding the provisions of section fifteen hundred twelve of this article, shall include (1) a risk retention group as defined in subsection (n) of section five thousand nine hundred two of the insurance law, (2) the state insurance fund and (3) a corporation, association, joint stock company or association, person, society, aggregation or partnership doing an insurance business as a member of the New York insurance exchange described in section six thousand two hundred one of the insurance law. The definition of the "state insurance fund" contained in this subdivision shall be limited in its effect to the provisions of this article and the related provisions of this chapter and shall have no force and effect other than with respect to such provisions. The term "insurance corporation" shall also include a captive insurance company doing a captive insurance business, as defined in subsections (c) and (b), respectively, of section seven thousand two of the insurance law; provided, however, "insurance corporation" shall not include the metropolitan transportation authority, or a public benefit corporation or not-for-profit corporation formed by a city with a population of one million or more pursuant to subsection (a) of section seven thousand five of the insurance law, each of which is expressly exempt from the payment of fees, taxes or assessments, whether state or local; and provided further "insurance corporation" does not include any combinable captive insurance company. The term "insurance corporation" shall also include an unauthorized insurer operating from an office within the state, pursuant to paragraph five of subsection (b) of section one thousand one hundred one and subsection (i) of section two thousand one hundred seventeen of the insurance law. The term "insurance corporation" also includes a health maintenance organization required to obtain a certificate of authority under article forty-four of the public health law.

(b) The term "domestic insurance corporation" means an insurance corporation incorporated or organized under the laws of this state. Provided, however, the savings banks life insurance fund and savings and insurance banks which are authorized to transact the business authorized by the provisions of article six-a of the banking law shall be subject to taxation as domestic insurance corporations on such insurance business under this article.

(c) The term "foreign insurance corporation" means an insurance corporation incorporated or organized under the laws of any other state of the United States, the District of Columbia or the Commonwealth of Puerto Rico.

(d) The term "alien insurance corporation" means an insurance corporation incorporated or organized under the laws of any other foreign nation, or of any province or territory not included under the definition of "foreign insurance corporation."

(e) The term "taxpayer" means any insurance corporation subject to the tax imposed under section fifteen hundred one, fifteen hundred two-a, or fifteen hundred ten or any captive insurance company subject to the tax imposed under section fifteen hundred two-b of this article.

(f) The term "taxable year" means the taxpayer's taxable year for federal income tax purposes, or the part thereof during which the taxpayer is subject to the tax under this article.

(g) The term "subsidiary" means a corporation of which over fifty percent of the number of shares of stock entitling the holders thereof to vote for the election of directors or trustees is owned by the taxpayer.

(h) The term "subsidiary capital" means investments in the stock of subsidiaries and any indebtedness from subsidiaries, exclusive of accounts receivable acquired in the ordinary course of trade or business for services rendered or for sales of property held primarily for sale to customers, whether or not evidenced by a written instrument, on which interest is not claimed and deducted by the subsidiary for purposes of taxation under any article of this chapter, provided, however, that in the discretion of the tax commission, there shall be deducted from subsidiary capital any liabilities payable by their terms on demand within one year from the date incurred, other than loans or advances outstanding for more than one year as of any date during the taxable year covered by the return, which are attributable to subsidiary capital.

(i) The term "investment capital" means investments in stocks, bonds and other securities, corporate and governmental, not held for sale to customers in the regular course of business, exclusive of subsidiary capital and stock issued by the taxpayer, provided, however, that in the discretion of the tax commission, there shall be deducted from investment capital any liabilities payable by their terms on demand or within one year from the date incurred, other than loans or advances outstanding for more than a year as of any date during the year covered by the return, which are attributable to investment capital, provided, also, there shall be excluded from investment capital, such investments which are held to maintain reserves of the taxpayer required under sections one thousand three hundred three, one thousand three hundred four and one thousand three hundred five of the insurance law.

(j) The term "business capital" means all assets, other than subsidiary capital, investment capital and stock issued by the taxpayer, less liabilities not deducted from subsidiary or investment capital which are payable by their terms on demand or within one year from the date incurred, other than loans or advances outstanding for more than a year as of any date during the year covered by the return, except that cash on hand and on deposit shall be treated as investment or as business capital as the taxpayer may elect, provided, however, that there shall be excluded from business capital such assets which are held to maintain reserves of the taxpayer required under sections one thousand three hundred three, one thousand three hundred four and one thousand three hundred five of the insurance law.

(k) The term "special risk premium" means any premium received on insurance provided the insurance is exempt from the filing requirements with respect to rates and policy forms pursuant to article sixty-three of the insurance law.