(a) For purposes of the tax imposed under this chapter, a taxpayer‘s taxable year shall be the same as such taxpayer’s taxable year for federal income tax purposes and a taxpayer’s method of accounting shall be the same as such taxpayer’s method of accounting for federal income tax purposes.

(b) If a taxpayer’s taxable year is changed for federal income tax purposes, the taxable year for purposes of the tax under this chapter shall be similarly changed. If a change in taxable year results in a taxable period of less than twelve months, the exemption allowed under § 12-702 shall be prorated under regulations adopted by the Commissioner of Revenue Services in accordance with chapter 54.

(c) If no method of accounting has been regularly used by the taxpayer, Connecticut taxable income shall be computed under such method that in the opinion of the commissioner, fairly reflects income. If a taxpayer’s method of accounting is changed for federal income tax purposes, the method of accounting for purposes of this chapter shall similarly be changed.

(d) In computing a taxpayer’s Connecticut taxable income for any taxable year under a method of accounting different from the method under which the taxpayer’s Connecticut taxable income for the previous year was computed, there shall be taken into account those adjustments which are determined, under regulations adopted by the commissioner, to be necessary solely by reason of the change in order to prevent amounts from being duplicated or omitted.

(e) If a taxpayer’s method of accounting is changed, other than from an accrual to an installment method, any additional tax which results from adjustments determined to be necessary solely by reason of the change shall not be greater than if such adjustments were ratably allocated and included for the taxable year of the change and the preceding taxable years, not in excess of two years, during which the taxpayer used the method of accounting from which the change is made. If a taxpayer’s method of accounting is changed from an accrual to an installment method, any additional tax for the year of such change of method and for any subsequent year which is attributable to the receipt of installment payments properly accrued in a prior year, shall be reduced by the portion of tax for any prior taxable year attributable to the accrual of such installment payments.