Partnerships (Form 1065) and S Corporations (Form 1120S) must report a bunch of additional crud on the generated K-1s. Just another tax return preparation fee hike courtesy of your Section 199A lawmakers.
Each partnership or S Corp must determine if any of its trades or businesses are specified service trades or businesses, and report this as such on the K-1. So now there is huge risk by the accounting firm preparing the K-1 for the partner or shareholder who is relying on that data for individual tax return preparation. Yes, there was always this risk, but now it is much larger since the SSTB determination will be one of the deciding factors in the Section 199A waterfall.
The K-1 will also have the partner or shareholder’s allocable share of qualified business income, W-2 wages and unadjusted basis immediately after acquisition of qualified property.
Taxpayer's Comprehensive Guide to LLCs and S Corps : 2019 Edition