business A an S-corp should be included in the QBI calculation. however only the net business profit or loss on the k-1 qualifies. wage's don't qualify as QBI however they are used in QBI calculation. it becomes even more complicated if the S_corp is a specified service business. what's more I have notice TT makes errors in computing the proper QBI deduction. I have called 4 times starting in March. 2 hang ups, spoke to EA and CPA even uploaded my return and there have been no corrections to the app as yet.
the S-Corp SE health should only reduce the S-corps qbi income on the K-1. there should have been a code on the k-1 to indicate the amount of the QBI. it is possible that the S-corp return was not prepared correctly which would make the K-1's incorrect.
let me give you an example of what I believe is the correct QBI calc (based on worksheet produce by a Big 10 University Tax Department)
s corp k-1 QBI $50000
s corp se health on w-2 $10000
s corp net qbi $40000 (a)
wages $300,000 only used in QBI calc if taxable income above amount for filing threshhold
business 2 QBI $100000 (b)
business 3 QBI (loss) ($25000) (c)
net QBI a+ b +c = $115000
qbi after business 3 loss reallocated to those with profit
S corp $32857
business 2 $82143
scorp qbi 20% of 32857 = 6571
business 2 qbi 20% of 82142 - 16429
total tentative qbi $23000 which is 20% of the $115,000
if your taxable income was $100000 your actual QBI deduction would be 20% of your taxable income since its lower than your qbi income
your numbers will work out much different bases on your actual situation
