103An entity shall recognise past service cost as an expense at the earlier of the following dates:

103 An entity shall recognise past service cost as an expense at the earlier of the following dates:
(a) when the plan amendment or curtailment occurs; and
(b) when the entity recognises related restructuring costs (see AASB 137) or termination benefits (see paragraph 165).
104 A plan amendment occurs when an entity introduces, or withdraws, a defined benefit plan or changes the benefits payable under an existing defined benefit plan.
105 A curtailment occurs when an entity significantly reduces the number of employees covered by a plan. A curtailment may arise from an isolated event, such as the closing of a plant, discontinuance of an operation or termination or suspension of a plan.
106 Past service cost may be either positive (when benefits are introduced or changed so that the present value of the defined benefit obligation increases) or negative (when benefits are withdrawn or changed so that the present value of the defined benefit obligation decreases).
107 Where an entity reduces benefits payable under an existing defined benefit plan and, at the same time, increases other benefits payable under the plan for the same employees, the entity treats the change as a single net change.