Section 220.42 - Methods of accounting(1) For purposes of this code, a taxpayer's method of accounting shall be the same as such taxpayer's method of accounting for federal income tax purposes, except as provided in subsection (3). If no method of accounting has been regularly used by a taxpayer, net income for purposes of this code shall be computed by such method as in the opinion of the department fairly reflects income.(2) If a taxpayer's method of accounting is changed for federal income tax purposes, the taxpayer's method of accounting for purposes of this code shall be similarly changed.(3) Any taxpayer which has elected for federal income tax purposes to report any portion of its income on the completed contract method of accounting under Treasury Regulation 1.451-3(b)(2) may elect to return the income so reported on the percentage of completion method of accounting under Treasury Regulation 1.451-3(b)(1), provided the taxpayer regularly maintains its books of account and reports to its shareholders on the percentage of completion method. The election provided by this subsection shall be allowed only if it is made, in such manner as the department may prescribe, not later than the due date, including any extensions thereof, for filing a return for the taxpayer's first taxable year under this code in which a portion of its income is returned on the completed contract method of accounting for federal tax purposes. An election made pursuant to this subsection shall apply to all subsequent taxable years of the taxpayers unless the department consents in writing to its revocation.s. 1, ch. 71-984; s. 9, ch. 72-278.