	Years ended December 31,
	2021		2020			2019
Base rents	$	92,738,000	$	95,987,000		$	105,041,000
Expense recoveries		31,022,000		29,241,000			33,475,000
Percentage rent		1,347,000		1,778,000			971,000
Straight-line rents		270,000		(1,208,000	)		405,000
Amortization of intangible lease liabilities, net		1,074,000		1,373,000			2,827,000
Total rents	$	126,451,000	$	127,171,000		$	142,719,000

The Company recognizes lease termination income when the following conditions are met: (1) the lease termination agreement has been executed, (2) the lease termination fee is determinable, (3) all the Company’s landlord services pursuant to the terminated lease have been rendered, and (4) collectability of the lease termination fee is assured. On January 31, 2020, the Company agreed to a cash

payment in consideration for permitting a dark anchor tenant to terminate its lease prior to the contractual expiration at Metro Square. As a result of this termination, revenues for 2020, included approximately $7.1 million of other income.

The Company reviews the collectability of charges under its tenant operating leases on a regular basis, taking into consideration changes in factors such as the tenant’s payment history, the financial condition of the tenant, business conditions in the industry in which the tenant operates and economic conditions in the area where the property is located. During 2021 and 2020, the Company’s assessment has specifically included the impact of the COVID-19 pandemic, which represents a material risk to collectability. In the event that collectability with respect to any tenant changes, the Company recognizes an adjustment to rental income. The Company’s review of collectability of charges under its operating leases includes any accrued rental revenues related to the straight-line method of reporting rental revenue. The Company identified various tenants where collection was no longer considered probable, and therefore, during the years ended December 31, 2021 and 2020, respectively, $0.7 million and $6.9 million of billed charges, consisting of rent and tenant reimbursements, were unpaid. Based on the Company’s determination to record revenue on a cash basis for these tenants, these amounts were not recorded as revenue.

Annual future base rents due to be received under non-cancelable operating leases in effect at December 31, 2021 are approximately as follows (excluding those base rents applicable to properties classified as real estate held for sale):

2022	$	87,221,000
2023		84,883,000
2024		74,689,000
2025		62,993,000
2026		51,829,000
Thereafter		201,182,000
	$	562,797,000

Total future minimum rents do not include expense recoveries for real estate taxes and operating costs, or percentage rents based upon tenants’ sales volume. Such additional revenue amounts aggregated approximately $32.5 million, $31.1 million and $34.4 million for 2021, 2020 and 2019, respectively. Such amounts do not include amortization of intangible lease liabilities.