Your paycheck may get fatter, but when?

Millions of working Americans should start seeing fatter paychecks as early as next month, Republican leaders say, as a result of the recently passed tax law.

But the precise timing hasn’t been fixed yet. And some employees should be aware that less money withheld doesn’t necessarily mean that their tax burden will shrink next year.

The massive Republican tax legislation, signed into law last month by President Trump, kicked in Jan. 1. Billed as a huge benefit for the stressed middle class, it brings the biggest overhaul of the US tax code in three decades, reaching into every corner of American society and the economy. The $1.5 trillion package provides generous tax cuts for corporations and the wealthiest Americans, and more modest reductions for middleand low-income individuals and families.

The Internal Revenue Service says employees could see “changes” in their paychecks as early as February. The agency first has to issue the new withholding tables for employers, reflecting the changes in tax rates for different income levels under the new law. That’s expected to happen sometime this month, to give companies and payroll service providers — and their computer systems — time to adjust. Such a massive, universal change feels something like turning around an aircraft carrier.

In the meantime, the pre-Jan. 1 tax rates and withholding amounts will continue to apply.

The IRS is “overwhelmed” by the changes in the complex new law and now is trying to get out the most important information first, said Melissa Labant, director of tax policy and advocacy at the American Institute of Certified Public Accountants.