: Using this balance can still create a margin loan. If you spend beyond your available cash by leveraging existing holdings, you will be charged margin interest on the borrowed amount.
: Assets bought with this balance are considered non-marginable, meaning the broker requires you to put up 100% of the purchase price upfront. non margin buying power
Cash Account Balances and Descriptions - Fidelity Investments : Using this balance can still create a margin loan
These assets generally carry higher volatility or lower liquidity, leading regulators and brokers to prohibit borrowing against them: non margin buying power