The following tables summarize activity in each of the net product revenue allowance and reserve categories described above for the nine months ended September 30, 2018 and 2017:

In thousands	Trade Allowances			Rebates, Chargebacks and Discounts			Product Returns			Other Incentives			Total
Balance as of December 31, 2017	$	12,035		$	32,064		$	1,887		$	2,107		$	48,093
Provision related to current period sales		30,814			128,905			812			14,636			175,167
Provision related to prior period sales		(660	)		(836	)		—			(69	)		(1,565	)
Credits/payments made for current period sales		(15,908	)		(76,015	)		—			(15,038	)		(106,961	)
Credits/payments made for prior period sales		(11,657	)		(29,594	)		(69	)		(2,297	)		(43,617	)
Balance as of September 30, 2018	$	14,624		$	54,524		$	2,630		$	(661	)	$	71,117

In thousands	Trade Allowances			Rebates, Chargebacks and Discounts			Product Returns			Other Incentives			Total
Balance as of December 31, 2016	$	3,743		$	20,915		$	859		$	1,681		$	27,198
Provision related to current period sales		24,780			87,499			1,496			10,796			124,571
Provision related to prior period sales		(297	)		(841	)		—			(82	)		(1,220	)
Credits/payments made for current period sales		(11,061	)		(62,014	)		(391	)		(8,834	)		(82,300	)
Credits/payments made for prior period sales		(3,107	)		(16,722	)		(24	)		(1,770	)		(21,623	)
Balance as of September 30, 2017	$	14,058		$	28,837		$	1,940		$	1,791		$	46,626