Almost every brokerage firm supports ACATS, which stands for Automated Customer Account Transfer Service, which lets you transfer your assets "in-kind." This means that your holdings are transferred without you having to sell them (and create a taxable event). If you have big unrealized gains in a stock, the shares just get moved over without you having to sell them and you keep the same cost basis. You may run into hiccups if some items can't be transferred. One common example is Vanguard Admiral shares of their mutual funds. Some brokerages will take them, others won't. In these cases, you may have to transfer them to another asset type (like the ETF version), which will accept them. ACATS does take a week or two to complete the transfer.