	December 31,
	2022			2021
Accounts receivable – commercial
Accounts receivable, gross	$	19,359		$	7,939
Wholesaler distribution fees and prompt pay discounts		(2,536	)		(1,696	)
Reserve for returns		(4,108	)		(2,797	)
Total accounts receivable – commercial, net		12,715			3,446
Accounts receivable – collaborations and services
Accounts receivable, gross		4,086			2,060
Allowance for credit losses		—			(767	)
Total accounts receivable – collaborations and services, net		4,086			1,293
Total accounts receivable, net	$	16,801		$	4,739

As of December 31, 2022 and December 31, 2021, the allowance for credit losses was de minimis. As of December 31, 2022 and December 31, 2021, the Company had three wholesale distributors representing approximately 74% and 80% of gross sales and 79% and 79% of accounts receivable, respectively.

As of December 31, 2022, there was no allowance for credit losses for accounts receivable – collaborations and revenue. The Company had one collaboration partner, United Therapeutics, that comprised 100% of the collaboration and services net accounts receivable as of December 31, 2022 and approximately 98% of gross revenue from collaborations and services for the year ended December 31, 2022.

The Company recognizes revenue net of gross-to-net adjustments. The activities and ending reserve balance consists of the following (in thousands):

	December 31,
	2022			2021
Prompt Pay Discount Reserve, Allowance for Wholesale Distribution Fees and Accounts Receivables Return Reserve:
Beginning balance	$	4,493		$	3,873
Provisions		17,471			11,494
Deductions		(15,320	)		(10,874	)
Ending balance	$	6,644		$	4,493