15 For the purposes of subsection 49(3) of the Act, where a person becomes entitled to a pension under any of Parts I to III of the Act and is required to contribute by instalments in respect of service for which no deductions have been made, during any period that the pension is not payable or is reduced to an amount that is not sufficient to pay the instalments in full, the unpaid portion of the remaining instalments shall be reserved from the pay and allowances or salary payable to the pensioner or from any other amount payable to him by Her Majesty.