Taxpayer is employed by large company. Due to miscalculations of fringe benefits, taxpayer had incorrect taxable income included in 2017 W-2. Taxpayer requested that employer correct W-2 and was advised that taxpayer would need to file an extension so that employer had time to correct. Now employer is stating that employer is unable to correct due to outdated payroll software and would like to balance out error in 2018. What would other tax preparers recommend to taxpayer in this situation?