"[IRS Chief Counsel Memorandum 2018-15] explains that the employer's satisfaction of its FICA and income tax withholding obligations in 2018 does not create additional compensation or wages for the employee for 2016. The employee receives no credit for the employer's belated payment of its income tax withholding liability, so the payment has no effect on the employee's 2016 income tax liability. The employer must report the employee's additional income for 2016 (the value of the taxable fringe benefit) on Form W-2c, but that form must not report the employer's payment as federal income tax withheld, or increase the employee's wages because of the employer's payment."