MUCH CONFUSION NOW!
In general the new tax law allows self-employed and owners of pass-through entities (partnerships and S Corps) to deduct 20% of "qualified business income".
The law is COMPLEX with limitations, exceptions and undefined terms.
Needs to define "qualified business income" more clearly. Specified service entities are subject to high income limitations. There is an issue wit tiered entities and whether or not Schedule E rental income is "qualified business income".
Expect guidance (hopefully clear guidance) late this year 2018.