On December 29, 2018, an employee received a $5,000 check from her employer’s client. The check was payable to the employer. The employee did not remit the funds to the employer until December 30, 2018. The employer deposited the check on December 31, 2018, but the bank did not credit the employer's bank account until January 2, 2019. When is the cash basis employer required to include the $5,000 in gross income?