Only Margin Accounts are able to sell a naked call option. Cash accounts can sell a naked put option, however there are certain restrictions.
Stock Options
Put Price + Maximum ((20% x Underlying Price - Out of the Money Amount),
(10% x Strike Price))
Index Options
Put Price + Maximum ((15% x Underlying Price - Out of the Money Amount),
(10% x Strike Price)
You can review and modify your account type in Client Portal.
Additional Information