Reviewing last years taxes -- Where would QBI be?

[Jacob P.]

Doing taxes last year, I brought everything to my accountant very excited about the 20% QBI deduction, and it seemed likely our rental properties would fall within all the "safe harbor" principals.

Over the phone, she explained her take to me. From what I recall, her points were

1. Complying with the new deduction as outlined in TCJA could be a bit complex
2. However, never fear, there is an existing deduction, which applies to "trade or businesses" which can benefit you the same way. 
3. As the owner of several rental properties, you qualify as a "trade or business" and we'll take that deduction.

All seemed good to me, and she told me this deduction was applied to our taxes.

This year I'm in the process of changing accountants, and trying to understand things myself a bit more thoroughly as part of the process. As I do some basic research, I'm having trouble finding what she might have been referring too. Does anyone have any clues as to where In my filed taxes I can see if and how such a deduction was taken (whether TCJA related or not?....)