	At December 31, 2020			At September 30, 2021
Computer and other related equipment	$	13,278		$	13,286
Purchased and internally developed software		2,058			2,846
Furniture and fixtures		1,271			1,271
Leasehold improvements		1,737			1,732
	$	18,344		$	19,135
Less: Accumulated depreciation and amortization		(15,597	)		(16,510	)
Property and equipment, net	$	2,747		$	2,625

We capitalize certain software development costs incurred in connection with developing or obtaining computer software for internal use when both the preliminary project stage is completed and it is probably that the software will be used as intended. Capitalized software costs include (i) external direct costs of materials and services utilized in developing computer software, (ii) compensation and related benefits for employees who are directly associated with the software projects. Capitalized software costs are amortized on a straight-line basis when place into service over the estimated useful lives of the software.

Depreciation and amortization expense related to property and equipment was approximately $363,000 and $278,000 for the three months ended September 30, 2020 and 2021, respectively. Depreciation and amortization expense related to property and equipment was approximately $1.2 million and $965,000 for the nine months ended September 30, 2020 and 2021, respectively.

	For the Nine Months Ended						For the Three Months Ended
	2020			2021			2020			2021
Interest Income	$	103		$	8		$	1		$	7
Interest Expense & Foreign Currency		(19	)		(45	)		(11	)		(14	)
Other		55			2,490			7			(14	)
Total	$	139		$	2,453		$	(3	)	$	(21	)

During the second quarter of 2021, we received $2.5 million related to a contractual settlement of an upside payment with previously divested properties.