<prompt> Human: So I came across this article which talks about the tax benefits of a 529 plan as a general purpose retirement vehicle after youve maxed out your 401k, 457, HSA, and IRA accounts.Looking at the basic math it does seem to make sense, if you had 100,000 in investments which doubled to 200,000 in value youd of course pay capital gains tax on the 100,000 in earnings. Which if we assume a long term capital gains tax would be taxed at the 20 rate instead of the short term marginal tax rate, which in this hypothetical scenario would be 20,000.The penalty for using a 529 for non-qualified withdrawals is of course 10, meaning that if it doubled youd also pay 20,000 in tax, but youd be tax exempt from ordinary dividends and interest while its in the account. Any earnings beyond this would actually be more tax beneficial in the 529 with paying the penalty than without.You can of course register in any states 529 plan and each state sets the contribution limits which is generally based on the price of a 4 year degree at the most expensive private school in that state, so that brings up the question, if you were to open multiple 529 plans in different state, could you stack each of the contribution limits to use the 529 plan? There is of course no annual contribution limit on any 529 plan, only the maximum dollar amount listed in that particular state.  <response>: NOOO.I have an overfunded 529 I inherited because Grandma was not blessed with the grandchildren she wanted.It has limited fund choice, and huge penalties. The only way Ive found to cash it out is the new tax bill loop hole of private K-12.Id take capital gains on a trust any day.If you are talking about this much money, just get a lawyer and make a trust. Do this correctly.Edit: The math missing from your post is the MARGINAL TAX RATE. Might not matter to you, matters to me. Hopefully, should matter in your retirement. 