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Exercise ISO or NSO in solo 401k?
You have a Solo 401(k). You can fund it with cash, or I believe, with shares of your own company. You can't pull in other assets such as the ISOs from another employer. I see why that's desirable, but it's not allowed.  You wrote "this will mitigate all tax complications with employee stock options."  But - you can't transfer the ISOs from your job into your Solo 401(k). As littleadv notes, it's self dealing. Once the ISO is exercised there's no hiding the gain into that 401(k).