Identifiable intangible assets consist of acquired customer contracts and relationships, trademarks, and non-compete agreements. Amortization expense related to intangible assets was $8.7 and $11.0 for the three months ended March 31, 2024 and 2023, respectively. Amortization expense related to intangible assets was $18.8 and $22.9 for the six months ended March 31, 2024 and 2023, respectively. These assets are amortized over their estimated useful lives of which the reasonableness is continually evaluated by the Company. The weighted average amortization periods of intangible assets acquired during the six months ended March 31, 2023 was seven years.

Intangible assets, net, as of March 31, 2024 and September 30, 2023 consisted of the following:


		March 31, 2024					September 30, 2023
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Customer relationships	6-21 yrs.	$	715.9	$	(603.2	)	$	725.5	$	(594.1	)
Trademarks	12 yrs.		—		—			3.8		(2.9	)
Non-compete agreements	5 yrs.		—		—			2.7		(2.7	)
Total intangible assets		$	715.9	$	(603.2	)	$	732.0	$	(599.7	)

The following is a summary of the goodwill activity for the periods ended September 30, 2023 and March 31, 2024:


	Maintenance Services			Development Services		Total
Balance, September 30, 2022	$	1,792.7		$	216.1	$	2,008.8
Acquisitions (1)		10.7			1.9		12.6
Balance, September 30, 2023	$	1,803.4		$	218.0	$	2,021.4
Acquisitions (1)		0.1			—		0.1
Divestiture		(5.8	)		—		(5.8	)
Balance, March 31, 2024	$	1,797.7		$	218.0	$	2,015.7

(1)

The acquisitions adjustment includes the immaterial impact of foreign currency adjustments during the period.

During the six months ended March 31, 2023, the Company acquired, through a series of separate transactions, 100% of the operations of three unrelated companies, all of which were allocated to Maintenance Services. The Company paid approximately $13.8 in aggregate consideration for the acquisitions, net of cash acquired. The Company accounted for the business combinations under the acquisition method and, accordingly, recorded the assets acquired and liabilities assumed at their estimated fair market values based on management’s preliminary estimates, with the excess allocated to goodwill. The purchase accounting related to these acquisitions was finalized within one year from each acquisition date. As a result of the final purchase accounting, certain of the fair value amounts previously estimated were adjusted during the measurement period. The fair values were primarily estimated using Level 3 assumptions within the fair value hierarchy, including estimated future cash flows, discount rates and other factors. The Company continued to refine the valuation data and estimates primarily related to unbilled revenue, property and equipment, intangible assets, net, accounts payable, accrued expenses and other current liabilities and deferred revenue and will finalize the amounts recognized as it obtains the information necessary to complete the analysis, but no later than one year from the acquisition date. The measurement period adjustments were not material to the Consolidated Balance Sheets as of March 31, 2024 and September 30, 2023. The identifiable assets acquired were primarily customer relationship intangible assets of $4.0. The amount allocated to goodwill is reflective of the benefits the Company expects to realize from anticipated synergies and the acquired assembled workforce. A portion of the goodwill resulting from these acquisitions is deductible for tax purposes.

On January 12, 2024, the Company completed the sale of one of its fully owned subsidiaries, U.S. Lawns, for total cash consideration of $51.6. The gain on the transaction of $43.9 is included in Gain on divestiture in the Consolidated Statement of Operations for the three and six months ended March 31, 2024. The Maintenance Services operating segment includes the operations of the divested entity, and its results of operations are included in the Consolidated Statement of Operations through January 12, 2024.