Commentary on Sections Structure of Chapters Overview
1939.Section 491 to 497 set out how to calculate a gain on a chargeable event other than one arising on any part surrender or part assignment, or an event in respect of the special charge for personal portfolio bonds.
1940.Section 491 introduces a number of terms which are used throughout the Chapter for the computation of gains (and defines them in subsection (4)). These are:
	“calculation event” (an umbrella term for events, the occurrence of which is dependent on the outcome of one of several prescribed calculations); and
	“excess event”, “part surrender or assignment event” and “personal portfolio bond event” (the types of event which may flow from such a calculation).