462When gains arise from policies and contractsU.K.
(1)For the purposes of this Chapter, a gain from a policy or contract arises when a chargeable event occurs in relation to the policy or contract (see section 484).
(2)But certain chargeable events are only treated as occurring because a calculation required to be made as at a particular time shows that the gain has arisen.
(3)See, in particular—
(a)section 509(1) (under which a chargeable event is treated as occurring where a periodic calculation following a part surrender or assignment shows a gain),
(b)section 514(1) (under which a part surrender or assignment is treated as a chargeable event where a calculation related to it shows a gain), and
(c)section 525(2) (under which a chargeable event is treated as occurring where an annual personal portfolio bond calculation shows a gain).