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Convention for adding ishares (ETFs) into personal accounts
What account you put it in depends on why you have those different accounts.  First, if you have them due to regulatory requirements, then you of course must follow said regulations. I doubt that's the case here.  Otherwise, you might be splitting based on how they trade (ETFs trade as stocks) or you could be splitting based on how you build a portfolio out of them.  When you build a non-speculative stock portfolio, you typically want to limit your holdings in a single stock to a fairly small portion of your portfolio (say, 3%) to limit your exposure to bad stuff happening to a single company. That doesn't apply nearly a much to mutual funds, especially index funds. ETFs are much more like mutual funds here.  You can also, of course, create an ETF account and put them there. You also say you have a market index account, what is that used for?