156.4. For the purposes of sections 156.1 to 156.3.1, the following rules apply:(a) the computation of income earned in Québec and of income earned in Québec and elsewhere is made in the manner prescribed in the regulations made pursuant to section 22, with the necessary modifications; and
(b) the computation of the business carried on in Canada, in Québec and in Québec and elsewhere by a corporation is made in the manner prescribed in the regulations made under subsection 2 of section 771, with the necessary modifications, and the computation of the business carried on in Canada, in Québec and in Québec and elsewhere by a partnership is made in the manner so prescribed in those regulations, with the necessary modifications, as if the partnership were a corporation and if its fiscal period were a taxation year.