26. Notwithstanding section 25, any lump sum paid as an increase or adjustment of the pensionable salary for a previous year shall form part of the pensionable salary for the year in which it is paid.
However, where the lump sum is paid in a year during which no service is credited, it shall be included in the pensionable salary of the last year during which service is credited prior to payment of the lump sum.
Any part of the lump sum that is attributable to an increase or adjustment of the salary paid to a pensioner for any period during which the pensioner is not an employee for the purposes of the plan, even if the pensioner holds pensionable employment under the plan, shall be excluded.