Product Revenue Reserves and Allowances

To date, the Company’s only source of product revenue has been from the U.S. sales of TYMLOS, which it began shipping to customers in May 2017. The following table summarizes activity in each of the product revenue allowance and reserve categories for the nine months ended September 30, 2018 and 2017 (in thousands):



	Chargebacks, Discounts, and Fees			Government and other rebates			Returns			Total
Beginning balance at December 31, 2017	$	1,986		$	1,231		$	421		$	3,638
Provision related to sales in the current year	9,750			15,350			229			25,329
Adjustments related to prior period sales	(76		)	(106		)	(111		)	(293		)
Credits and payments made	(8,971		)	(9,257		)	(236		)	(18,464		)
Ending balance at September 30, 2018	$	2,689		$	7,218		$	303		$	10,210

Beginning balance at December 31, 2016	$	—		$	—		$	—		$	—
Provision related to sales in the current year	688			459			296			1,443
Adjustments related to prior period sales										—
Credits and payments made										—
Ending balance at September 30, 2017	$	688		$	459		$	296		$	1,443

Chargebacks, discounts, fees, and returns are recorded as reductions of trade receivables, net on the condensed consolidated balance sheets. Government and other rebates are recorded as a component of accrued expenses and other current liabilities on the condensed consolidated balance sheets. The total provision related to sales for 2018 of $25.3 million is comprised of $6.1 million, $8.6 million, and $10.6 million, respectively, for activity during the quarters ended March 31, June 30, and September 30, 2018. The total adjustments related to prior period sales in 2018 of $293 thousand is comprised of $245 thousand, $(29) thousand, and $77 thousand, respectively, for the quarters ended March 31, June 30, and September 30, 2018. The total credits and payments made for 2018 of $18.5 million is comprised of $3.0 million, $6.7 million, and $8.8 million, respectively, for activity during the quarters ended March 31, June 30, and September 30, 2018.