Revenue The Company adopted ASC 606 effective January 1, 2018 using the modified retrospective method. The Company recognized the cumulative effect of initially applying ASC 606, which was immaterial, as an adjustment to the opening balance of retained earnings. The comparative prior period information is accounted for in accordance with the previous revenue guidance, ASC 605, and has not been restated. In accordance with ASC 606, the Company recognizes revenue under the core principle to depict the transfer of control to the Company’s customers in an amount reflecting the consideration the Company expects to be entitled. In order to achieve that core principle, the Company applies the following five step approach: (1) identify the contract with a customer, (2) identify the performance obligations in the contract, (3) determine the transaction price, (4) allocate the transaction price to the performance obligations in the contract and (5) recognize revenue when a performance obligation is satisfied. Revenue for product sales is recognized at the point in time when control transfers to the Company’s customers, which is generally when products are shipped from the Company’s manufacturing facilities or when delivered to the customer’s named location. When the Company performs shipping and handling activities after the transfer of control to the customer (e.g., when control transfers prior to delivery), they are considered to be fulfillment activities, and accordingly, the costs are accrued for when the related revenue is recognized. Taxes collected on behalf of customers relating to product sales and remitted to governmental authorities, principally sales taxes, are excluded from revenue. The opening and closing balances of the Company’s accounts receivable and deferred revenue are as follows (in thousands): The amount of revenue recognized in the period that was included in the opening deferred revenue balances was approximately$5.1 million for the year ended December 31, 2019. Generally, increases in current and non-current deferred revenue are related to billings to, or advance payments from, customers for which the Company has not yet fulfilled its performance obligations, and decreases are related to revenue recognized. Deferred revenue not expected to be recognized within the Company’s operating cycle of one year is presented as a component of “Other long-term liabilities” on the consolidated balance sheet. At times, the Company receives orders for products that may be delivered over multiple dates that may extend across reporting periods. The Company invoices for each delivery upon shipment and recognizes revenues for each distinct product delivered, assuming transfer of control has occurred. Generally, scheduled delivery dates are within one year, and the Company has elected to use the optional exemption whereby revenues allocated to partially completed contracts with an expected duration of one year or less are not disclosed. As of December 31, 2019, the Company had no contracts with unsatisfied performance obligations with a duration of more than one year.

Balance at Beginning of

Period (1/1/19)	Increase / (Decrease)	Balance at End of Period

Year Ended December 31, 2019

Accounts receivable	$90,831	$7,117	$97,948

Deferred revenue (current)	$5,101	$(618)	$4,483

Deferred revenue (non-current)	$3,707	$(263)	$3,444

Question: What is excluded when calculating revenue?
Answer: Taxes collected on behalf of customers relating to product sales and remitted to governmental authorities, principally sales taxes