CGT event F3 happens if a lessor incurs expenditure in getting the lessee's agreement to vary or waive a term of the lease. The lessor makes a capital loss equal to the amount of expenditure it incurred. (The expenditure can include giving property: see section 103-5.)
The time of the event is when the term is varied or waived.
However, this event does not apply to expenditure for a lease to which the lessor has chosen to apply section 104-115.