From the Summary: "Congress made numerous changes to the federal tax code for individuals and corporate and noncorporate businesses in December 2017, as part of P.L. 115-97 (referred to in this report as the 2017 tax revision but also known as the Tax Cuts and Jobs Act). At the core of the law was a permanent cut in the corporate income tax rate from a top rate of 35% to a flat rate of 21%. During the congressional debate over the 2017 tax revision, pass-through business owners sought tax relief comparable to any reduction in corporate tax rates. Heeding this request, Congress added a new deduction under Section 199A of the federal tax code. The deduction allows pass-through business owners to deduct up to 20% of their qualified business income (QBI) in determining their personal tax liability. This reduces effective tax rates for pass-through business profits by up to 20%. Like most of the changes in the individual income tax in P.L. 115-97, the new Section 199A deduction is temporary: it is available from 2018 to 2025. In general, Section 199A allows individuals, trusts, and estates with pass-through business income to deduct up to 20% of their QBI from their taxable income."
CRS Report for Congress, R46402
Congressional Research Service: https://crsreports.congress.gov/