Negative Balance Protection

A rule or account feature ensuring a retail client cannot lose more than the money in their trading account.

Example

After an extreme price gap, a protected account closes at zero rather than owing the broker money.

It is required for retail CFD clients in some jurisdictions but not universal, so check whether it applies to your account.

Margin call — A demand from a lender for more cash or collateral because the value of a leveraged position has fallen far enough that the equity in it is below the required level.
Leverage — Investing with borrowed money so that you control more of an asset than your own capital would buy. Gains and losses are both multiplied by the same factor.
Contract for Difference (CFD) — A leveraged contract with a provider that pays or charges the change in an asset's price, without owning the asset.

Leverage, gaps, the broker itself, and a tax treatment that depends on the product — The biggest forex risks are leverage and sudden gaps. Costs include spreads and overnight financing, and tax treatment varies widely by product and country. (11 min)