No special structure would be required . A fund can accept capital gain and non-capital gain monies into the same fund. Let's call this a mixed investment. It will create significant additional accounting. If you identify to the Opportunity Zone fund manager a mixed investment, the fund manager will be able to calculate your investment as two separate investments. This would be similar to investing both IRA and non-IRA money into a limited partnership. If the fund manager is not notified, the investor will need to allocate all reporting as though it came from two separate investments. This separate accounting will be needed for the initial deferral and separate basis calculations. When the fund sells after 10 years, the portion not from a capital gain would be taxable if there were a gain. The portion of gain originally from a capital gain would tax-free. If there were a death, the portion not from a capital gain would get stepped up in basis to market value of the investment upon death. The portion from the capital gain would not get a step up in basis until 10 years passed. The bottom line is that you should notify the fund manager if any amounts invested are not from a capital gain. The manager is better able to handle the accounting than the investor.