See Note 2 for a description of the Company’s revenue recognition accounting policy.

The following table disaggregates revenue generated within the United States (U.S.) from revenue generated from customers outside of the U.S. Revenue for transaction tax compliance in the U.S. is further disaggregated based on the solutions or services purchased by customers. Total revenues consisted of the following (in thousands):

	For the Three Months Ended March 31,
	2020		2019
Revenue (U.S.):
Subscription and returns
Tax determination	$	58,971	$	45,232
Tax returns and compliance management		39,433		26,686
Interest income on funds held for customers		525		729
Total subscription and returns		98,929		72,647
Professional services		5,462		5,735
Total revenue (U.S.)		104,391		78,382
Total revenue (non-U.S.)		7,052		6,588
Total revenue	$	111,443	$	84,970

Timing may differ between the satisfaction of performance obligations and the invoicing and collection of amounts related to contracts with customers. Liabilities are recorded for amounts that are collected in advance of the satisfaction of performance obligations. To the extent a contract exists, as defined by ASC 606, these liabilities are classified as current and non-current deferred revenue. To the extent that a contract does not exist, as defined by ASC 606 (e.g. customer agreements with non-standard termination rights), these liabilities are classified as contract liabilities. Contract liabilities are transferred to deferred revenue at the point in time when the criteria that establish the existence of a contract are met.

A summary of the activity impacting the contract liabilities during the three months ended March 31, 2020 is presented below (in thousands):

	Three Months Ended March 31,
	2020			2019
Contract liabilities:
Balance beginning of period	$	5,197		$	—
Adoption of ASC 606		—			2,090
Contract liabilities transferred to deferred revenue		(2,538	)		(1,257	)
Addition to contract liabilities		3,671			3,375
Balance end of period	$	6,330		$	4,208

As of March 31, 2020, contract liabilities are expected to be transferred to deferred revenue within the next 12 months and therefore are included in accrued expenses on the consolidated balance sheets.

A summary of the activity impacting deferred revenue balances during the three months ended March 31, 2020 is presented below (in thousands):

	Three Months Ended March 31,
	2020			2019
Deferred revenue:
Balance beginning of period	$	161,241		$	134,653
Adoption of ASC 606		—			(11,250	)
Revenue recognized		(111,443	)		(84,970	)
Additional amounts deferred		115,571			94,281
Balance end of period	$	165,369		$	132,714

Assets are recognized for the incremental costs of obtaining a contract with a customer if the benefit of those costs is expected to be longer than one year. These deferred commissions are amortized over an expected period of benefit of generally six years.

A summary of the activity impacting the deferred commissions during the three months ended March 31, 2020 is presented below (in thousands):

	Three Months Ended March 31,
	2020			2019
Deferred commissions:
Balance beginning of period	$	38,416		$	—
Adoption of ASC 606		—			19,267
Additional commissions deferred		4,897			7,656
Amortization of deferred commissions		(2,647	)		(1,279	)
Balance end of period	$	40,666		$	25,644

As of March 31, 2020, $9.7 million of deferred commissions are expected to be amortized within the next 12 months and therefore are included in current assets on the consolidated balance sheets. The remaining amount of deferred commissions are included in noncurrent assets. There were no impairments of assets related to deferred commissions during the three months ended March 31, 2020. There were no assets recognized related to the costs to fulfill contracts during the three months ended March 31, 2020 as these costs were not material.

Contracts with customers include amounts allocated to performance obligations that will be satisfied at a later date. These amounts include additional performance obligations that are not yet recorded in the consolidated balance sheets. As of March 31, 2020, amounts allocated to these additional contractual obligations are $39.4 million, of which $39.0 million is expected to be recognized as revenue over the next 12 months with the remaining amount thereafter.