The Company offers payment terms of more than one year for qualified customers and transactions in some circumstances. At times, revenue recognition occurs before billing, resulting in an unbilled receivable, which represents a contract asset. The contract asset is a component of accounts receivable and other assets for the current and non-current portions, respectively.

Customer advances represent deposits from customers for shipments of systems. Deferred revenue balances represent active and non-active warranties and services, which are recognized based on contract terms.

	December 31, 2019		June 30, 2019
(Dollars in thousands)	Amount		Amount
Contract Assets:
Unbilled accounts receivable – current (1)	$	11,530	$	5,260
Interest receivable – current (2)		640		361
Long-term accounts receivable (3)		3,478		4,116
Interest receivable – non-current (3)		1,288		1,255
Contract Liabilities:
Customer advances		18,231		20,395
Deferred revenue – current		79,599		78,332
Deferred revenue – non-current		27,242		26,639

During the quarter ended December 31, 2019, contract assets changed primarily due to the timing of billings occurring after revenues were recognized and payment terms exceeding 12 months. Contract liabilities changed due to timing of system sales for which the warranty has not yet started and was deferred and due to changes in transaction price.

	Three Months Ended			Six Months Ended
(Dollars in thousands)	December 31, 2019			December 31, 2019
Balance at beginning of period	$	105,869		$	104,971
New billings		99,796			190,272
Recognition of deferred revenue from opening balance		(15,753	)		(26,944	)
Recognition of new additions		(83,072	)		(161,459	)
Balance at end of period	$	106,840		$	106,840

Remaining performance obligations represent deferred revenue from open contracts for which performance has already started and the transaction price from executed and non-cancellable contracts for which performance has not yet started. Service contracts in general are considered month-to-month contracts, and therefore, the Company has elected the practical expedient to not disclose the value of unsatisfied performance obligations for contracts with an original expected duration of one year or less.

As of December 31, 2019, total remaining performance obligations amounted to $935.4 million. Of this total amount, $83.9 million related to long-term warranty and service, which is expected to be recognized over the remaining warranty period for systems that have

been delivered. For systems that have been delivered but not yet installed, management estimates the timing of installation since warranty starts upon installation.

The following table represents the Company's remaining performance obligations related to long-term warranty and service as of December 31, 2019 and the estimated revenue expected to be recognized:

	Fiscal years of revenue recognition
(Dollars in thousands)	2020		2021		2022		Thereafter
Long-term warranty and service	$	17,914	$	31,645	$	19,200	$	15,136

For the remaining $851.5 million of performance obligations, the Company estimates 19% to 28% will be recognized in the next 12 months, and the remaining portion will be recognized in the 30 months thereafter. The Company’s historical experience indicates that some of its customers will cancel or renegotiate contracts as economic conditions change or when product offerings change during the long sales cycle. Based on historical cancellations, approximately 14% of the Company’s contracts may never result in revenue due to cancellation.

The time bands reflect management’s best estimate of when the Company will transfer control to the customer and may change based on timing of shipment, readiness of customers’ facilities for installation, installation requirements, and availability of products.

The Company capitalizes and amortizes the incremental costs of obtaining a contract, primarily related to certain bonuses and sales commissions. The capitalized bonuses and sales commissions are amortized over a period of five years commencing upon the initial transfer of control of the system to the customer following the pattern of transfer of control of the performance obligations to the customer.

The balance of capitalized costs to obtain a contract was $9.1 million and $8.4 million as of December 31, 2019 and June 30, 2019, respectively. The Company has classified the capitalized costs to obtain a contract as a component of prepaid expenses and other current assets and other assets with respect to the current and non-current portions of capitalized costs, respectively, on the consolidated balance sheets. The Company incurred impairment losses of $0 and $0.1 million in the three and six month periods ended December 31, 2019. The Company incurred a de minimis impairment loss for the three and six month period ended December 31, 2018. During the three and six months ended December 31, 2019, the Company recognized $0.5 million and $1.0 million, respectively, in expense related to the amortization of the capitalized contract costs. During the three and six months ended December 31, 2018, the Company recognized $0.4 million and $1.3 million, respectively, in expense related to the amortization of the capitalized contract costs.