Subject to sections 98F and 98G, an increase payable by virtue of this Part in the rate of a pension benefit that was, or is, under subsection 98B(7), to be treated as having been, payable to a person on 30 June or 31 December (as the case requires) in a half - year applies in relation to the instalment of pension benefit falling due on the first pension pay - day occurring after that day and in relation to all subsequent instalments.