The proposed regulations state the following: Section 1400Z-2(e)(4)(B) authorizes regulations to ensure that a QOF has “a reasonable period of time to reinvest the return of capital from investments in qualified Opportunity Zone stock and qualified Opportunity Zone partnership interests, and to reinvest proceeds received from the sale or disposition of qualified Opportunity Zone business property.” For example, if a QOF shortly before a testing date sells qualified opportunity zone property, that QOF should have a reasonable amount of time in which to bring itself into compliance with the 90 percent asset test. The transactions that may trigger the inclusion of gain that has been deferred under a section 1400Z-2(a) election are the “reasonable period” (see section 1400Z-2(e)(4)(B)) for a QOF to reinvest proceeds from the sale of qualifying assets without paying a penalty; administrative rules applicable under section 1400Z-2(f) when a QOF fails to maintain the required 90 percent investment standard; and information-reporting requirements under section 1400Z-2. A reasonable period time has not been defined in the proposed regulations, but I would guess at a minimum it is 90 days, and at a max it would revert to the original 180 days.