The Company’s accounts receivable arises from sales on credit to customers. The Company establishes an allowance for credit losses to present the net amount of accounts receivable expected to be collected. With the adoption of Topic 326 on January 1, 2020, the allowance is determined by using the loss-rate method, which requires an estimation of loss rates based upon historical loss experience adjusted for factors that are relevant to determining the expected collectability of accounts receivables. Some of these factors include macroeconomic conditions that correlate with historical loss experience, delinquency trends, aging behavior of receivables and credit and liquidity indicators for individual customers. Prior to the adoption, the Company established the allowance under an incurred loss mode, considering the aging of the accounts receivable, the credit worthiness of each distributor based on payment history, and general economic factors, among other factors.

	December 31,			September 30,
	2019			2020
				(unaudited)
Trade accounts receivable	$	58,774		$	54,322
Other receivables		434			454
Total receivables		59,208			54,776
Less: Allowance for credit losses		(580	)		(910	)
Receivables, net	$	58,628		$	53,866

	Year ended December 31,			Nine months ended September 30,
	2019			2020
				(unaudited)
Beginning balance	$	503		$	580
Increase, charged to expense		333			210
Recoveries		(204	)		(71	)
Provision for late fee charges		—			191
Amounts written-off		(52	)		—
Ending balance	$	580		$	910

	December 31,			September 30,
	2019			2020
				(unaudited)
Finished goods	$	42,402		$	29,046
Raw materials		4,227			5,900
Gross inventory		46,629			34,946
Less: Excess and obsolete provision		(4,959	)		(5,892	)
Inventories, net	$	41,670		$	29,054

The following table reflects the activity in the Company’s inventory excess and obsolete provision (in thousands):

	Year ended December 31,			Nine months ended September 30,
	2019			2020
				(unaudited)
Beginning balance	$	3,950		$	4,959
Inventory written off		(149	)		(1,537	)
Increase in excess and obsolete provision		1,158			2,470
Ending balance	$	4,959		$	5,892

	December 31,		September 30,
	2019		2020
			(unaudited)
Accrued goods and services	$	8,364	$	8,436
Accrued inventory purchases		3,094		4,261
Accrued customer rebates		3,569		7,064
Other		7		10
Accrued liabilities	$	15,034	$	19,771

Provisions for warranty claims are primarily related to our hardware products and are recorded at the time products are sold. The change to accrued warranty was as follows (in thousands):

	Year ended December 31,		Nine months ended September 30,
	2019		2020
			(unaudited)
Beginning balance	$	488	$	706
Warranties assumed due to acquisition		180		1,174
Fulfillment of assumed acquisition warranty		—		(387	)
Provision increase, net		38		282
Ending balance	$	706	$	1,775

At December 31, 2019, $0.7 million is included in Other current liabilities on the Company’s condensed consolidated balance sheet. At September 30, 2020, $1.1 million is included in Other current liabilities and $0.7 million is included in Other noncurrent liabilities on the Company’s condensed consolidated balance sheet.