Identifiable intangible assets consist of acquired customer contracts and relationships, trademarks and non-compete agreements. Amortization expense related to intangible assets was $12.0 and $12.5 for the three months ended March 31, 2022 and 2021, respectively. Amortization expense related to intangible assets was $25.5 and $26.4 for the six months ended March 31, 2022 and 2021, respectively. These assets are amortized over their estimated useful lives of which the reasonableness is continually evaluated by the Company. The weighted average amortization period of intangible assets acquired during the six months ended March 31, 2022 is seven years.

Intangible assets as of March 31, 2022 and September 30, 2021 consisted of the following:


		March 31, 2022					September 30, 2021
	Estimated Useful Life	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Customer relationships	6-21 yrs.	$	711.7	$	(524.8	)	$	694.9	$	(499.8	)
Trademarks	12 yrs.		3.8		(2.5	)		3.8		(2.3	)
Non-compete agreements	5 yrs.		2.7		(1.9	)		2.7		(1.7	)
Total intangible assets		$	718.2	$	(529.2	)	$	701.4	$	(503.8	)

The following is a summary of the goodwill activity for the periods ended September 30, 2021 and March 31, 2022:


	Maintenance Services		Development Services		Total
Balance, September 30, 2020	$	1,680.4	$	178.9	$	1,859.3
Acquisitions		77.6		13.9		91.5
Balance, September 30, 2021	$	1,758.0	$	192.8	$	1,950.8
Acquisitions (1)		30.1		36.9		67.0
Balance, March 31, 2022	$	1,788.1	$	229.7	$	2,017.8

(1)

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

During the six months ended March 31, 2022, the Company acquired, through a series of separate transactions, 100% of the operations of six unrelated companies, one of which was allocated between Maintenance Services and Development Services. The Company paid approximately $84.4 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 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 valuation process to determine fair values is not yet complete. The Company 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 identifiable assets acquired were primarily customer relationship intangible assets of $16.8. The amount allocated to goodwill is reflective of the benefits the Company expects to realize from anticipated synergies and the acquired assembled workforce. The Company expects a portion of the goodwill resulting from these acquisitions will be deductible for tax purposes.

During the six months ended March 31, 2021, the Company acquired, through a series of separate transactions, 100% of the operations of four unrelated companies, of which two were allocated between both Maintenance Services and Development Services. The Company paid approximately $75.7 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 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 identifiable assets acquired were primarily customer relationship intangible assets of $18.0. The amount allocated to goodwill is reflective of the benefits the Company expects to realize from anticipated synergies and workforce in place. The Company expects a portion of the goodwill resulting from these acquisitions will be deductible for tax purposes.