Employers should begin using the 2018 withholding tables as soon as possible, but not later than Feb. 15, 2018. They should continue to use the 2017 withholding tables until implementing the 2018 withholding tables.
Many employees will begin to see increases in their paychecks to reflect the new law in February. The time it will take for employees to see the changes in their paychecks will vary depending on how quickly the new tables are implemented by their employers and how often they are paid — generally weekly, biweekly or monthly.
The new withholding tables are designed to work with the Forms W-4 that workers have already filed with their employers to claim withholding allowances. This will minimize burden on taxpayers and employers. Employees do not have to do anything at this time.
The new law makes a number of changes for 2018 that affect individual taxpayers. The new tables reflect the increase in the standard deduction, repeal of personal exemptions and changes in tax rates and brackets. The new tables are designed to produce the correct amount of tax withholding and are also intended to avoid over- and under-withholding of tax.
Check with your tax advisor as to whether or not you should adjust your withholding by filing a new Form W-4.