Revenue from contracts with customers is recognized when, or as, the Company satisfies its performance obligations by delivering the promised goods or service deliverables to the customers. A good or service deliverable is transferred to a customer when, or as, the customer obtains control of that good or service deliverable. A performance obligation may be satisfied over time or at a point in time. Revenue from a performance obligation satisfied over time is recognized by measuring the Company’s progress in satisfying the performance obligation in a manner that depicts the transfer of the goods or services to the customer. Revenue from a performance obligation satisfied at a point in time is recognized at the point in time that the Company determines the customer obtains control over the promised good or service deliverable. The amount of revenue recognized reflects the consideration the Company expects to be entitled to in exchange for those promised goods or services (i.e., the “transaction price”). In determining the transaction price, the Company considers multiple factors, including the effects of variable consideration. Variable consideration is included in the transaction price only to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainties with respect to the amount are resolved. In determining when to include variable consideration in the transaction price, the Company considers the range of possible outcomes, the predictive value of its past experiences, the time period of when uncertainties expect to be resolved and the amount of consideration that is susceptible to factors outside of the Company’s influence, such as the judgment and actions of third parties.

The Company had product and product-related services revenue consisting of revenue from the sale of instruments and consumables and the use of the HTG EdgeSeq proprietary technology to process samples and design custom RUO assays for the years ended December 31, 2018 and 2017 as follows:

	Years Ended December 31,
	2018		2017
Product revenue:
Instrument	$	351,885	$	385,143
Consumables		1,964,499		1,463,347
Total product revenue		2,316,384		1,848,490
Product-related services revenue:
Custom RUO assay design		964,241		419,515
Sample processing		5,840,765		4,529,250
Total product-related services revenue		6,805,006		4,948,765
Total product and product-related services revenue	$	9,121,390	$	6,797,255

Because the Company’s agreements for product and product-related services revenue have an expected duration of one year or less, the Company has elected the practical expedient in ASC 606-10-50-14(a) to not disclose information about its remaining performance obligations.

The delivery of each instrument and related installation and calibration are considered to be a single performance obligation, as the HTG EdgeSeq instrument must be professionally installed and calibrated prior to use. Instrument product revenue is generally recognized upon installation and calibration of the instrument by field service engineers, which represents the point at which the customer has the ability to use the instrument and has accepted the asset. Installation generally occurs within one month of instrument shipment.

The delivery of each consumable is a separate performance obligation. Consumables revenue is recognized upon transfer of control, which represents the point when the customer has legal title and the significant risks of ownership of the asset. The Company’s standard terms and conditions provide that no right of return exists for instruments and consumables, unless replacement is necessary due to delivery of defective or damaged product. Customer payment terms vary but are typically between 30 and 90 days of revenue being earned from shipment or delivery, as applicable.

Shipping and handling fees charged to the Company’s customers for instruments and consumables shipped are included in the accompanying consolidated statements of operations as part of product and product-related services revenue. Shipping and handling costs for sold products shipped to the Company’s customers are included in the accompanying consolidated statements of operations as part of cost of product and product-related services revenue.

For sales of consumables in the United States, standard delivery terms are FOB shipping point, unless otherwise specified in the customer contract, reflecting transfer of control to the customer upon shipment. The Company has elected the practical expedient to account for shipping and handling as activities to fulfill the promise to transfer the consumables.

The Company provides instruments to certain customers under reagent rental agreements. Under these agreements, the Company installs instruments in the customer’s facility without a fee and the customer agrees to purchase consumable products at a stated price over the term of the agreement; in some instances, the agreements do not contain a minimum purchase requirement. Terms range from several months to multiple years and may automatically renew in several month or multiple year increments unless either party notifies the other in advance that the agreement will not renew. The Company measures progress toward complete satisfaction of its performance obligation to provide the instrument and deliver the consumables using an output method based on the number of consumables delivered in relation to the total consumables to be provided under the reagent rental agreement. This is considered to be representative of the delivery of outputs under the arrangement and the best measure of progress because the customer benefits from the instrument only in conjunction with the consumables. The Company expects to recover the cost of the instrument under the agreement through the fees charged for consumables, to the extent sold, over the term of the agreement.

In reagent rental agreements, the Company retains title to the instrument and title is transferred to the customer at no additional charge at the conclusion of the initial arrangement. The cost of the instrument is amortized on a straight-line basis over the term of the arrangement, unless there is no minimum consumable product purchase, in which case the instrument would be expensed as cost of product and product-related services revenue upon installation. Cost to maintain the instrument while title remains with the Company is charged to selling, general and administrative expense as incurred.

The Company also provides sample preparation and processing services and molecular profiling of retrospective cohorts for its customers through its VERI/O laboratory, whereby the customer provides samples to be processed using HTG EdgeSeq technology specified in the order. Customers are charged a per sample fee for sample processing services which is recognized as revenue upon delivery of a data file to the customer showing the results of testing and completing delivery of the agreed upon service. This is when the customer can use and benefit from the results of testing and the Company has the present right to payment.

The Company enters into custom RUO assay design agreements that may generate up-front fees and subsequent payments that might be earned upon completion of design process phases. The Company measures progress toward complete satisfaction of its performance obligation to perform custom RUO assay design using an output method based on the costs incurred to date compared to total expected costs, as this is representative of the delivery of outputs under the arrangements and the best measure of progress. However, because in most instances the assay development fees are contingent upon completion of each phase of the design project and the decision of the customer to proceed to the next phase, the amount to be included in the transaction price and recognized as revenue is limited to that which the customer is contractually obligated to pay upon completion of that phase, which is when it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur. Changes in estimates of total expected costs are accounted for prospectively as a change in estimate. From period to period, custom RUO assay design service revenue can fluctuate substantially based on the completion of design-related phases.

See Note 16 for discussion of collaborative development services contracts with related parties. There was $0 and $25,000 of collaborative development services revenue generated from the Company’s companion diagnostic development services agreements with non-related party customers for the years ended December 31, 2018 and 2017, respectively.

The Company receives up-front payments from customers for custom RUO assay design services, and occasionally for sample processing services. Payments for instrument extended warranty contracts are made in advance as are payments for certain agreed-upon capital purchases required for collaborative development service projects. The Company recognizes such up-front payments as a contract liability. The contract liability is subsequently reduced at the point in time that the data file is delivered for sample processing services or as the Company satisfies its performance obligations over time for RUO assay design, collaborative development and extended warranty services. Contract liabilities of $410,947 and $837,885 were included in contract liabilities – current and other non-current liabilities in the accompanying consolidated balance sheets as of December 31, 2018 and 2017, respectively.

Changes in the Company’s contract liability were as follows as of the date indicated:

	Product Revenue			Custom RUO Assay Design			Sample Processing			Collaborative Development Services			Total Contract Liability
Balance at January 1, 2018	$	39,426		$	197,606		$	490,536		$	110,317		$	837,885
Deferral of revenue		190,703			448,580			197,541			70,918			907,742
Customer deposits		131,864			—			—			—			131,864
Recognition of deferred Revenue		(245,446	)		(596,186	)		(443,677	)		(181,235	)		(1,466,544	)
Balance at December 31, 2018	$	116,547		$	50,000		$	244,400		$	—		$	410,947