18-125-810 Me. Code R. § .06
The gross tax is calculated by applying the Maine corporate income tax rates provided in 36 M.R.S. §5200 against the net income of the unitary group. The gross tax is then adjusted by multiplying that amount by the apportionment factor of the unitary group, the product of which is the Maine tax liability for the nexus members of the unitary group.
If separate returns are filed, each filing member applies its separate apportionment factor, as calculated under section .05(B) above, against the gross tax to determine the member's Maine tax liability. If an alternate assignment of tax liability is elected by the assignment of the preferential rates provided in 36 M.R.S. §5200 to a specific member or members, the associated reduction of tax liability must result in an equal increase of tax liability to one or more other members of the unitary group. The sum of tax liabilities of the separate filing members must equal the Maine tax liability that would have been imposed on the nexus members of the unitary group if a single return was filed.
18-125 C.M.R. ch. 810, § .06