@sjrcpa is on the right track.  It would be helpful to have some numbers here.  Let's say the property sold for $1 million, with a basis of $100K, so a $900K gain. The two DST's (apparently Delaware Statutory Trust must replace Daylight Savings Time in our vocabulary) cost $600K.  So, $500K gain rolled over and basis of those two items is $100K.  The other $400K is "boot" that would be taxable gain, had it not gone into the QOZ property.