Book profit computation clarified: accounting basis, revaluation reserve adjustment, and life insurance income excluded from the section. Amendment requires companies to compute book profit using Part II of Schedule VI unless the proviso to section 211 mandates application of the Act governing the company; adds revaluation reserve on retirement or disposal of revalued assets as an adjustment; confirms a prior option for affected companies to follow Part II and Part III of Schedule VI or their governing Act for certain assessment years; and excludes life insurance business income (as referred to in section 115B) from the scope of the section.