CheapTrade, an accrual basis, calendar year corporation, operates a discount securities brokerage business. CheapTrade accepts orders to buy or sell marketable securities for its customers and charges them a commission fee for effecting the transaction in a timely, low-cost manner. CheapTrade executes an order on the "trade" date, but title to the securities is not legally transferred, and payment to or from the customer is not due until the "settlement date." In the normal five-day interval between the trade and settlement dates, CheapTrade performs administrative and accounting functions to record the transaction. During the last week of 2017, CheapTrade effected over 18,000 transactions with a trading date in 2017 but a settlement date in 2018. Cheap Trade's commission from these transactions was $1,712,400. In which year should CheapTrade recognize this income?