WASHINGTON — The year’s end is always a frantic time for tax preparers. This year, it’s more frenetic than usual. The tax-cut bill, coming so late in the year, has whipped up a mild panic for accountants, payroll staffs and anyone who handles taxes.

The Internal Revenue Service released new tax-withholding tables Friday, a little more than two weeks before the new year begins. But payroll processors say the delay in the withholding schedules means the wrong amounts may be taken out of many workers’ paychecks in the first few weeks of January.

Accounting firms are rushing to advise clients, master the tax-code revisions and update software.

Jim Bolek, an executive at Basic Payrolls Plus in Grand Rapids, Mich., which processes paychecks at 400 companies, says the delay in the 2011 tax-withholding tables has been giving him heartburn.

The IRS said it recognizes that late-in-the-year changes in the tax code pose problems for payrolls. It said employers should start using the new tax-withholding tables by Jan. 31. If employers withhold too much in taxes during January, they should repay workers by the end of March, the IRS said.

The bill will, among other things, extend income-tax cuts for two years; renew long-term unemployment aid; reduce workers’ Social Security taxes in 2011; and let companies increase write-offs for capital investments next year.

IRS Commissioner Doug Shulman warned lawmakers earlier this month not to wait until 2011 — after taxpayers have begun filing returns — to make retroactive changes. Doing so would pose an “unprecedented and daunting operational challenge” for the IRS and taxpayers, he said.

Shulman’s biggest concern was a legislative “patch” that would spare 20 million taxpayers from the alternative minimum tax. The AMT is designed to ensure that high-income people don’t use deductions and credits to avoid income tax. Its income thresholds have never been pegged to inflation, so each year Congress fixes the AMT to spare many middle-income people from tax increases.

In 2007, a late fix to the AMT by Congress forced the IRS to delay processing some AMT-related forms until mid-February 2008. The IRS had to scramble to update its computers, and potential refunds for up to 13.5 million people were held up.

This time, the IRS programmed its computers to assume Congress would patch the AMT again.