NOTE O — ACCRUED EXPENSES, OTHER CURRENT LIABILITIES AND OTHER LIABILITIES

Accrued expenses and other current liabilities consists of:

	As of December 31,
(in thousands)	2017		2016

Patient prepayments deposits and refunds payable	$	30,194	$	28,895
Accrued sales taxes and other taxes	6,335		5,716
Accrued professional fees	11,612		25,912
Insurance and self-insurance accruals	8,901		9,866
Other current liabilities	8,796		8,561

Total	$	65,838	$	78,950

Patient prepayment deposits and refunds includes funds received for devices not yet delivered to a patient and refunds for overpayments. Taxes primarily includes accrued sales tax liabilities and other taxes payable. Accrued professional fees primarily relate to accruals for professional accounting and legal fees. Accrued insurance primarily relates to accruals for estimated losses for certain self-insured risks including property, professional liability, general liability and employee health care costs. Other current liabilities are primarily related to accruals for deferred revenue and warranty liabilities.

Other liabilities consists of:

	As of December 31,
(in thousands)	2017		2016

Supplemental executive retirement plan obligations	$	21,842	$	21,478
Unrecognized tax benefits	5,219		5,015
Long-term insurance accruals	9,531		9,088
Deferred tenant improvement allowances	7,361		7,345
Deferred rent	4,909		5,433
Asset retirement obligations	1,180		1,464
Other	211		894

Total	$	50,253	$	50,717

Supplemental executive retirement plan obligations includes obligations due on both the DB SERP and DC SERP. See Note K - “Employee Benefits” within these consolidated financial statements. Unrecognized tax benefits represent the difference between tax positions that we expect to take, or take on our income tax returns and the benefit we recognize on our financial statements. Deferred tenant improvement allowance represents deferred credits associated with receiving lease incentives. Deferred rent represents net deferred credits associated with recognizing rent expense on a straight-line basis for property operating leases whose lease payments escalate over the life of the lease. Both deferred credits are recognized as reductions of rent expense over the term of the associated lease. Asset retirement obligations is the liability to return a leased building to the state before it was occupied. Other includes fair market value lease differential liability, build-to-suit tenant interest accrual and other long-term accrued expenses.