QBI safe harbor is for rental real estate activities that would be reported on schedule E. It's a tax regulation that, if the conditions are met, allows you to treat rental real estate activities as qualifying for the QBI that the IRS can not challenge. If you don't meet all the conditions, that doesn't mean the activities don't qualify for the QBI. But in that case, the IRS can challenge the QBI deduction.
https://www.cbiz.com/insights/articles/article-details/the-rental-real-estate-safe-harbor-for-qbi-de...
