Workers will see changes in their February paychecks once employers adopt the new guidance, the news release said.
"We have reviewed this very carefully, and based upon last year's withholding tables, approximately 76 percent of taxpayers were withheld so that they had refunds at the end of the year".
Earlier this week, Wyden and Rep. Richard Neal, the top Democrat on the House tax-writing committee, asked the Government Accountability Office to analyze the new IRS tables to see if they might lead to systematic underwithholding of federal taxes from paychecks. With these new guidelines, companies can start adjusting employee paychecks.
In the meantime, he urged filers who have complicated tax situations - i.e., anyone who is not single, childless and holding down just one job - to review the number of allowances they now take on their W4s once the IRS puts out its new withholding calculator by the end of February.
Despite less withholding, it is also expected that tax returns will not be effected.
To ensure an accurate calculation, taxpayers will have to enter their personal financial information into a calculator expected to be unveiled next month on the website IRS.gov. Among those changes are an increase in the standard deduction, new tax brackets and more.
"While these withholding tables are created to work with Forms W-4 that employees have already provided to employers, it is possible that taxpayers may need to make changes to their Forms W-4", Jennifer Breen, a partner in Morgan, Lewis & Bockius LLP's Washington office, said in an email.
Treasury Secretary Steven Mnuchin at the White House press briefing on Thursday dismissed suspicions that administration is "juicing" the tables as a "ridiculous charge".
The IRS is not issuing new Form W-4s ... yet.
"We would encourage every taxpayer to run their information through the calculator". You might not have bothered looking at it since then and you should take this opportunity to review your withholdings and see if it is time to make some changes.
But the taxing service did note that the new tax rates will require a new approach to the W-4 forms and that it should have the new forms by 2019.
The agency said it is revising the Form W-4 and the online employee withholding calculator to reflect the new tax law, including changes in available itemized deductions, increases in the child tax credit, the new dependent credit, and the repeal of dependent exemptions.