Here is a clip from the Washington Post on pass-throughs.
“Pass through” companies get a 20 percent reduction: Most American businesses are organized as “pass through” companies in which the income from the business is “passed through” to the business owner's individual tax return. S corporations, LLCs, partnerships and sole proprietorships are all examples of pass-through businesses. In the final GOP bill, the majority of these companies get to deduct 20 percent of their income tax-free, a large reduction that mirrors what was in the Senate bill. The changes, however, expire after 2025. The National Federation of Independent Business initially opposed the House version, arguing that it didn't do enough for small businesses. But the NFIB later endorsed the House and Senate plans. Service businesses such as law firms, doctor's offices and investment offices can take only the 20 percent deduction if they make up to $315,000 (for married couples).
My question is... is that $315k of income for the business or for the AGI?