The tables are designed to work with W-4 forms on file. However, the IRS is also revising those forms.

The new W-4s and revised withholding tax calculator will reflect changes in the law such as available itemized deductions, increases in the child tax credit, the new dependent credit and repeal of dependent exemptions. Many employees will begin to see increases in their paychecks reflecting the new law in February. The IRS anticipates this calculator should be available by the end of February.

More information is available in the Withholding Tables Frequently Asked Questions.