Tax payers and advisors require immediate guidance from the U.S. Treasury and the Internal Revenue Service on 39 areas of the new tax law, the American Institute of Certified Public Accountants said Monday. The one-month old Tax Cuts and Jobs Act revised many sections of the Internal Revenue Code, creating uncertainty for both companies and individuals as they transition to the new rules, the AICPA said in a letter. Urgent guidance is needed for key areas such as the definition of a business,...

There may be few tidings of comfort and joy among those preparing corporate balance sheets should Congress pass—and President Donald Trump sign—the tax bill on or before Dec. 25. In some cases, companies may have to rifle through three decades of records. House and Senate Republicans reached a deal on the final tax bill last week, paving the way for lawmakers to vote on the measure before Christmas. The agreement would set the corporate tax rate at 21%, down from the current 35%, and it would...