FuelCell Energy Inc (FCEL)

[Maximilliano]

You can only short with a margin account.

Not to get too technical, but the idea of shorting is to sell stocks you don't have by borrowing them from someone else. This is why interest is charged.

In a cash account, you must pay for a security in full when you buy it...and thus before selling it. You can't borrow funds from your brokerage firm to pay for transactions in the cash account. If you intend to trade using borrowed funds, you must open a margin account to trade. You can't sell short with a cash account.