The IRS recently released proposed regulations aimed at setting out the rules and regulations for the new Section 199A 20% business deduction; https://www.irs.gov/newsroom/irs-issues-proposed-regulations-on-new-20-percent-deduction-for-passthrough-businesses , all 184 pages of them.
The new laws and regulations pertain to domestic businesses operated as sole proprietorships, partnerships, S corporations, trusts, and estates; corporations do not qualify. The rules are effective for tax years after 2017 and before 2026. One reason for pressing ahead on the release was to set out procedures for taxpayers who need to aggregate separate business activities for the calculation. There are a great number of specific rules and ownership percentage tests, so meet with your tax professional for guidance that is appropriate for your business structure as you plan.
The deduction is for the lesser of the “Combined qualified business income amount” of the taxpayer, or 20% of the excess of taxable income for the tax year over the sum of net capital gains and aggregated amounts of qualified cooperative dividends. Again, there are a number of qualifications, especially for the trusts and estates, and you will want to consult with your licensed tax professional when making planning decisions.