I've always understood that there is a very rare situation in which K-1 income in an IRA is taxable - If the amount in box 20V (unrelated business income) is greater than a certain amount ($1000 if I recall). This is very rare - I receive several K-1s and have never had this happen. Usually it's a negative number. Brokers with which I had K-1 issuers in IRA's used to ask me to upload the K-1's for this, and then I'd get a notice to the effect that "good news you don't owe any tax on your K-1's" (which I already knew) several months later.
