If states simply do nothing in response to federal tax reform, most will experience an increase in revenue due to
the provisions of the federal tax reform bill. That’s
because the base-broadening provisions flow through to most state tax codes, but the corresponding rate reductions do not. And now we discover that one significant base narrower—the pass-through deduction—won’t affect most states, either.
That provision provides a 20 percent deduction against qualified pass-through business income for those with incomes below $315,000 (joint filers). For filers above that threshold, the deduction is limited to the greater of (a) 50 percent of wage income or (b) 25 percent of wage income plus 2.5 percent of the cost of tangible depreciable property, and many service businesses are excluded. (The benefit phases out between $315,000 and $415,000.)
https://taxfoundation.org/pass-deduction-wont-flow-states/
it is structured as a deduction against taxable income, not adjusted gross income (AGI). That matters because
27 states use federal AGI as their starting point for taxation, while only six begin with federal taxable income. The remaining states which impose individual income taxes either use federal gross income or a state-specific calculation. This means that while 41 states tax wage income, only six of them have to worry about the pass-through deduction.
Those six states are Colorado, Michigan, Minnesota, North Dakota, South Carolina, and Vermont, and it’s a good bet that legislators in those states will be thinking about decoupling from the pass-through deduction.