Intangible Assets

During the three and six months ended March 31, 2019, the Company recorded indefinite-lived intangible assets not subject to amortization of $2.7 million related to the joint venture transaction discussed in Note 17.

The gross and net carrying values of intangible assets as of the balance sheet dates, by major intangible asset class are as follows (in millions):



	March 31, 2019							September 30, 2018
	Gross Amount		Accumulated Amortization			Net Amount		Gross Amount		Accumulated Amortization			Net Amount
Intangible assets subject to amortization:
Software programs/platforms	$	2.7	$	(2.6	)	$	0.1	$	2.7	$	(2.6	)	$	0.1
Customer base	21.4		(11.4		)	10.0		21.4		(10.1		)	11.3
Total intangible assets subject to amortization:	$	24.1	$	(14.0	)	$	10.1	$	24.1	$	(12.7	)	$	11.4

Intangible assets not subject to amortization:
Business licenses	$	2.7	$	—		$	2.7	$	—	$	—		$	—
Total intangible assets not subject to amortization:	$	2.7	$	—		$	2.7	$	—	$	—		$	—
Total intangible assets	$	26.8	$	(14.0	)	$	12.8	$	24.1	$	(12.7	)	$	11.4

Amortization expense related to intangible assets was $1.3 million and $1.1 million for the six months ended March 31, 2019 and 2018, respectively. Amortization expense related to intangible assets was $0.6 million for the three months ended March 31, 2019 and 2018.

As of March 31, 2019, the estimated future amortization expense was as follows:



(in millions)
Fiscal 2019 (remaining six months)	$	1.3
Fiscal 2020	2.2
Fiscal 2021	2.2
Fiscal 2022	1.0
Fiscal 2023 and thereafter	3.4
	$	10.1