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Where are open-end funds traded?
I assume that mutual funds are being discussed here. As Bryce says, open-ended funds are bought from the mutual fund company and redeemed from the fund company.  Except in very rare circumstances,  they exist only  as bits in the fund company's computers and not as share certificates (whether paper or electronic) that can be delivered from the selling broker to the buying broker on a stock exchange. Effectively, the fund company is the sole market maker: if you want to buy, ask the fund company at what price it will sell them to you (and it will tell you the answer only after 4 pm that day when a sale at that price is no longer possible unless you committed to buy, say, 100 shares and authorized the fund company to withdraw the correct amount from your bank account or other liquid asset after the price was known).  Ditto if you want to sell: the mutual fund company will tell you what price it will give you only after 4 pm that day and you cannot sell at that price unless you had committed to accept whatever the company was going to give you for your shares (or had said "Send me $1000 and sell as many shares of mine as are needed to give me proceeds of $1000 cash.")