Intangible assets were as follows (RMB in millions):


	2021			2022
Intangible assets to be amortized
Business Relationship (Representing the relationship with the travel service providers and other business partners)		1,872			1,872
Technology		610			610
Others		799			799
Intangible assets not subject to amortization
Trade mark		11,764			11,776
Others		159			161

		15,204			15,218

Less: accumulated amortization
Intangible assets to be amortized
Business Relationship		(1,342	)		(1,485	)
Technology		(588	)		(610	)
Others		(314	)		(381	)

		(2,244	)		(2,476	)

Net book value
Intangible assets to be amortized
Business Relationship		530			387
Technology		22			—
Others		485			418
Intangible assets not subject to amortization
Trade mark		11,764			11,776
Others		159			161

		12,960			12,742

Indefinite-lived intangible assets are not subject to legal, regulatory, contractual, competitive, economic or other limitation on their useful lives. The Company evaluates to determine whether events and circumstances continue to support an indefinite useful life in each reporting period.

Finite-lived intangible assets are tested for impairment if impairment indicators arise. The Company amortizes its finite-lived intangible assets over their estimated economic useful lives using the straight-line method:


Business Relationship			5-10 years
Technology			5-10 years
Others			3-15 years

Amortization expense for the years ended December 31, 2020, 2021 and 2022 was approximately RMB424 million, RMB295 million and RMB240 million respectively.

The annual estimated amortization expense for intangible assets subject to amortization for the five succeeding years is as follows (RMB in millions):


	Amortization
2023		186
2024		181
2025		155
2026		51
2027		51

		624