53.20. A lump sum paid as an increase in or adjustment to the pensionable salary for a previous year included in the pensionable salary established under sections 25 to 29 for the year during which the lump sum is paid must be distributed among the years for which the lump sum is paid if it is paid after 31 December 2006.
If the pensionable salary is reduced under the second paragraph of section 29, the part of the lump sum included in the pensionable salary is distributed for each year concerned in the proportion obtained by dividing the part of the lump sum referred to in section 26 and attributed to a given year by the lump sum referred to in that section.