Accounts receivable, net consists of the following (in thousands):


	December 31, 2023			December 31, 2022
Accounts receivable – commercial
Accounts receivable, gross	$	20,199		$	19,359
Wholesaler distribution fees and prompt pay discounts		(2,469	)		(2,536	)
Reserve for returns		(6,215	)		(4,108	)
Allowance for credit losses		(157	)		—
Total accounts receivable – commercial, net		11,358			12,715
Accounts receivable – collaborations and services		3,543			4,086
Total accounts receivable, net	$	14,901		$	16,801

As of December 31, 2023 , the allowances for credit losses and doubtful accounts for commercial accounts receivable of $0.2 million was related to $0.2 million of accounts receivable for Zealand. As of December 31, 2022, the allowances for credit losses and doubtful accounts for commercial accounts receivable was de minimis. As of December 31, 2023 and 2022, the Company had three wholesale distributors representing approximately 85% and 74% of gross sales and 74% and 79% of commercial accounts receivable, respectively.

As of December 31, 2023, there was no allowance for credit losses for accounts receivable for collaborations and services. The Company had one collaboration partner, UT, that comprised 100% of the collaboration and services net accounts receivable as of December 31, 2023 and approximately 100% and 98% of gross revenue from collaborations and services for the years ended December 31, 2023 and 2022, respectively.

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


	December 31, 2023			December 31, 2022
Prompt Pay Discount Reserve, Allowance for Wholesale Distribution Fees and Accounts Receivable Reserves:
Beginning balance	$	6,644		$	4,493
Provisions		18,977			17,471
Deductions		(16,780	)		(15,320	)
Ending balance	$	8,841		$	6,644