Risk warning: Trading Forex (foreign exchange) or CFDs (contracts for difference) on margin carries a high level of risk and may not be suitable for all investors. There is a possibility that you may sustain a loss equal to or greater than your entire investment. Therefore, you should not invest or risk money that you cannot afford to lose. Before using Admiral Markets UK Ltd, Admiral Markets Cyprus Ltd or Admiral Markets PTY Ltd services, please acknowledge all of the risks associated with trading.
As we've already stated, trading on margin is trading on money borrowed from your broker. Each time you open a trade on margin, your broker automatically allocates the required margin from your existing funds in the trading account in order to back the margin trade. The precise amount of allocated funds depends on the leverage ratio used on your account.

The "philosophy" of the forex trading system, as with the rest of the QuantStart site, is to try and mimic real-life trading as much as possible in our backtesting. This means including the details that are often excluded from more "research oriented" backtesting situations. Latency, server outages, automation, monitoring, realistic transaction costs will all be included within the models to give us a good idea of how well a strategy is likely to perform.
Multiple Currency Pairs - Similarly we need to support the major currency pairs beyond "Cable" (GBP/USD). There are two aspects to this. The first is to correctly handle the calculations when neither the base or quote of a currency pair is equal to the account denomination currency. The second aspect is to support multiple positions so that we can trade a portfolio of currency pairs.
Brokers use margin levels in an attempt to detect whether FX traders can take any new positions or not. Different brokers have varying limits for the margin level, but most will set this limit at 100%. This limit is called a margin call level. Technically, a 100% margin call level means that when your account margin level reaches 100%, you can still close your positions, but you cannot take any new positions.

Trading on a margin can have varying consequences. It can influence your trading experience both positively and negatively, with both profits and losses potentially being seriously augmented. Your broker takes your margin deposit and then pools it with someone else's margin Forex deposits. Brokers do this in order to be able to place trades within the whole interbank network.