
At December 31, 2024	Cost		Accumulated amortization		Net book value
Trade names and trademarks	$	220.5	$	(63.2)	$	157.3
Customer relationships	2,538.1		(393.7)		2,144.4
Software and technology assets	781.1		(416.9)		364.2
Software under development	2.8		—		2.8

	$	3,542.5	$	(873.8)	$	2,668.7


At December 31, 2023	Cost		Accumulated amortization		Net book value
Trade names and trademarks	$	221.9	$	(29.7)	$	192.2
Customer relationships	2,553.1		(225.0)		2,328.1
Software and technology assets	670.4		(285.5)		384.9
Software under development	8.9		—		8.9

	$	3,454.3	$	(540.2)	$	2,914.1

At December 31, 2024, a net carrying amount of $52.7 million (December 31, 2023: $59.0 million) included in intangible assets was not subject to amortization, $49.9 million of which relates to certain trade names and trademarks and the remainder relates to software under development.

During the year ended December 31, 2024, interest of $1.0 million (2023: $1.6 million; 2022: $0.4 million) was capitalized to the cost of software under development.

At December 31, 2024, estimated annual amortization expense for the next five years ended December 31 are as follows:


2025	$	340.2
2026	319.3
2027	244.9
2028	192.9
2029	178.7
	$	1,276.0