美股市场偶尔会发生极端波动和价格混乱。 有时这类情况持续时间很长，有时又很短。止损单可能会对价格施加下行压力、加剧市场波动，且可能使委托单在大幅偏离触发价格的位置上成交。 

美式期权卖方（沽出方）在期权到期前随时可能会被行权。也就是说，期权卖方在卖出期权后到期权到期或通过买回期权将头寸平仓这段时间随时可能会被行权。看涨或看跌期权所有者在期权到期前调用其权利即为提早行权。作为期权卖方，您无法控制期权被行权，也无法知晓其会何时发生。通常，越临近到期，被行权的风险越大，但即使这样，美式期权交易仍然随时会发生被行权。

空头看跌期权
卖出看跌期权时，卖方有义务在指定时间窗口内（到期日）以约定价格（行使价）买入底层股票或资产。如果期权的行使价低于股票的当前市价，则期权持有者把股票卖给期权卖方并不会获利，因为市场价格比行使价要高。反过来，如果期权的行使价高于股票的当前市价，则期权卖方就会有被行权的风险。

空头看涨期权
卖出看涨期权后，看涨期权的所有者有权在给定时间范围内以约定价格从期权卖方买入股票。如果股票的市价低于期权的行使价，则对看涨期权持有者来说，以高于市价的价格买入股票没有任何好处。但如果股票的市价高于期权的行使价，则期权持有者可以低于市价的价格买入股票。如果期权处于价内或如果即将派息且空头看涨期权的内在价值低于股息，则空头看涨期权会有被行权风险。

期权会发生什么？
如果空头看涨期权被行权，则空头看涨期权持有者将被分配空头股票。例如，如果ABC公司的股价为$55，行使价为$50的空头看涨期权被行权，则空头看涨期权将会转换成价格为$50的空头股票。然后账户持有人可以决定以$55的价格买回股票平仓空头头寸。100股的净损失会是$500，再减去最开始卖出看涨期权时收到的权利金。

如果空头看跌期权被行权，则空头看跌期权持有者相当于是以看跌期权行使价多头持有股票。例如，XYZ的股价为$90，空头看跌期权卖方按行使价$96被分配了股票，则看跌期权卖方有责任以$96（高于市价）的价格买入股票。假设账户持有人以$90的价格平仓了多头股票头寸，那么100股的净损失会是$600，再减去最开始卖出看跌期权时收到的权利金。

期权被行权导致保证金不足
如果被行权发生在期权到期之前并且产生的股票头寸导致保证金不足，则根据我们的保证金政策，账户将面临自动平仓清算以重新满足保证金要求。平仓清算并不只限于期权被行权产生的股票头寸。

此外，对于期权价差的空头边被行权的账户，IBKR不会将其持有的多头期权行权。IBKR无法推测多头期权持有者的意图，并且在到期前行使多头期权将导致放弃期权的时间价值（时间价值通过卖出期权实现）。

到期后风险敞口、公司行动和除息
盈透证券会根据到期时间或公司行动相关事件采取积极措施降低风险。有关我们到期政策的更多信息，请阅读知识库文章“到期&公司行动相关清算”。

账户持有人应参阅“标准期权的特征与风险”披露文件，IBKR在账户申请时便向所有有期权交易资格的客户提供了此文件，其中明确说明了被行权风险。此文件还可在期权清算公司（OCC）网站上查看。

1 杠杆限制

1.1 ESMA保证金
ESMA针对不同的底层证券设置了不同的杠杆限制：

• 货币对为3.33%；主要货币对为美元、加元、欧元、英镑、瑞郎、日元间的任意组合
• 非主要货币对及主要指数为5%；
  • 非主要货币对为包括上方未列出的货币的任意组合，如美元/离岸人民币
  • 主要指数为IBUS500、IBUS30、IBUST100、IBGB100、IBDE40、IBEU50、IBFR40、IBJP225、IBAU200
• 非主要股票指数为10%，包括IBES35、IBCH20、IBNL25、IBHK50
• 个股为20%

 1.2应用的保证金 - 标准保证金要求

除ESMA的保证金要求外，IBKR（英国）还基于底层证券的历史波动率及其它因素实施其自有的保证金要求（IB保证金） 如果IB的保证金率高于ESMA规定的比例，则应用IB的保证金率。

点此可查看适用的IB和ESMA保证金要求详情。

1.2.1应用的保证金 - 最低集中保证金要求

如果您的投资组合包含一小部分CFD头寸，或者如果最大的两种头寸占据了绝大多数份额，则您的账户将应用集中保证金。我们会通过对最大的两种头寸假设30%的跌幅、对其余头寸假设5%的跌幅来对您的投资组合进行压力测试。如果总亏损额高于标准要求，则将用总亏损额作为维持保证金要求。

1.3可用于初始保证金的资金

您只可使用现金作为初始保证金开立差价合约头寸。已实现的差价合约盈利将包括在现金中且立即可用；现金无需先结算。然而，未实现的盈利不得用于满足初始保证金要求。

1.4自动转移资金以满足初始保证金要求（账户F账户段）

IBKR（英国）会自动将您主账户中的资金转移至账户的F账户段，用于满足差价合约的初始保证金要求。

然而，需注意的是，系统不会转移资金用于满足差价合约维持保证金要求。因此，如符合条件的资产（参照下方定义）不足以满足保证金要求，则即使您的主账户中有足够的资金，账户仍会被清算。如您想避免被清算，您必须在账户管理中将多余的资金转移至账户的F账户段。

2 保证金平仓规则

2.1维持保证金计算与清算

如果符合条件的资产跌至开仓初始保证金的50%以下，ESMA要求IBKR最后清算差价合约仓位。如果我们的风险观更为保守，IBKR可能会更早平仓仓位。符合条件的资产包括F账户段下的现金（不包括账户任何其它账户段下的现金）及未实现的差价合约盈亏（盈利及亏损）。

计算的基础为开立差价合约头寸时存入的初始保证金。 换言之，当差价合约头寸的价值发生变动时，初始保证金的金额不会变化，这与非差价合约头寸适用的保证金计算方式不同。

2.1.1举例

您的差价合约账户中有2000欧元现金。您想以100欧元的限价买入100份XYZ的差价合约。首先成交了50份合约，然后再成交其余的50份。随着您的交易成交，您的可用现金如下减少：

*净资产等于现金加未实现盈亏

价格上涨至110。您的净资产现为3000，但由于您的可用现金仍为0，且在ESMA规则下初始保证金和维持保证金不变，您不得开立新的头寸：

 然后价格下跌至95。您的净资产跌至1500，但鉴于净资产仍大于1000，无需追加保证金：

价格进一步跌至85，导致保证金不足并触发清算：

3 负资产保护

ESMA规则规定，您交易差价合约的损失以划拨的专项资金为上限。不得清算其它金融产品（如股票或期货）来填补差价合约的保证金缺口。*

因此，您主账户证券和大宗商品账户段的资产，以及F账户段中持有的非差价合约资产不列入差价合约交易的风险资本。但是，F账户段中的所有现金都可用以弥补差价合约交易产生的亏损。

由于负资产保护对IBKR来说意味着要承担额外风险，对于隔夜持有的差价合约头寸我们会向零售客户额外收取1%的融资息差。您可在此处查看详细的差价合约融资利率。

*我们无法清算非差价合约头寸来弥补差价合约不足，但可以清算差价合约头寸来弥补非差价合约不足。

4 交易差价合约的激励措施

ESMA规定对与差价合约交易相关的金钱及某些非金钱激励均予以禁止。IBKR不对交易差价合约提供任何奖金或其它激励。

1 Leverage Limits

1.1 ESMA Margins
Leverage limits were set by ESMA at different levels depending on the underlying:

• 3.33% for major currency pairs; Major currency pairs are any combination of USD; CAD; EUR; GBP; CHF; JPY
• 5% for non-major currency pairs and major indices;
  • Non-major currency pairs are any combination that includes a currency not listed above, e.g. USD.CNH
  • Major indices are IBUS500; IBUS30; IBUST100; IBGB100; IBDE40; IBEU50; IBFR40; IBJP225; IBAU200
• 10% for non-major equity indices; IBES35; IBCH20; IBNL25; IBHK50
• 20% for individual equities

 1.2 Applied Margins - Standard Requirement

In addition to the ESMA Margins, IBKR (UK) establishes its own margin requirements (IB Margins) based on the historical volatility of the underlying, and other factors. We will apply the IB Margins if they are higher than those prescribed by ESMA.

Details of applicable IB and ESMA margins can be found here.

1.2.1 Applied Margins - Concentration Minimum

A concentration charge is applied if your portfolio consists of a small number of CFD positions, or if the three largest positions have a dominant weight. We stress the portfolio by applying a 30% adverse move on the three largest positions and a 5% adverse move on the remaining positions. The total loss is applied as the maintenance margin requirement if it is greater than the standard requirement.

1.3 Funds Available for Initial Margin

You can only use cash to post initial margin to open a CFD position. Realized CFD profits are included in cash and are available immediately; the cash does not have to settle first. Unrealized profits however cannot be used to meet initial margin requirements.

1.4 Automatic Funding of Initial Margin Requirements (F-segments)

IBKR (UK) automatically transfers funds from your main account to the F-segment of your account to fund initial margin requirements for CFDs.

Note however that no transfers are made to satisfy CFD maintenance margin requirements. Therefore if qualifying equity (defined below) becomes insufficient to meet margin requirements, a liquidation will occur even if you have ample funds in your main account. If you wish to avoid a liquidation you must transfer additional funds to the F-segment in Account Management.

2 Margin Close Out Rule

2.1 Maintenance Margin Calculations & Liquidations

ESMA requires IBKR to liquidate CFD positions latest when qualifying equity falls below 50% of the initial margin posted to open the positions. IBKR may close out positions sooner if our risk view is more conservative. Qualifying equity for this purpose includes cash in the F-segment (excluding cash in any other account segment) and unrealized CFD P&L (positive and negative).

The basis for the calculation is the initial margin posted at the time of opening a CFD position. In other words, and unlike margin calculations applicable to non-CFD positions, the initial margin amount does not change when the value of the open position changes.

2.1.1 Example

You have EUR 2000 cash in your CFD account. You want to buy 100 CFDs of XYZ at a limit price of EUR 100. You are first filled 50 CFDs and then the remaining 50. Your available cash reduces as your trades are filled:

*Equity equals Cash plus Unrealized P&L

The price increases to 110. Your equity is now 3000, but you cannot open additional positions because your available cash is still 0, and under the ESMA rules IM and MM remain unchanged:

 The price then drops to 95. Your equity declines to 1500 but there is no margin violation since it is still greater than the 1000 requirement:

The price falls further to 85, causing a margin violation and triggering a liquidation:

3 Negative Equity Protection

The ESMA Decision limits your CFD-related liability to the funds dedicated to CFD-trading. Other financial instruments (e.g. shares or futures) cannot be liquidated to satisfy a CFD margin-deficit.*

Therefore assets in the security and commodity segments of your main account, and non-CFD assets held in the F-segment, are not part of your capital at risk for CFD trading. However, all cash in the F-segment can be used to cover losses arising from CFD trading.

As Negative Equity Protection represents additional risk to IBKR, we will charge retail investors an additional financing spread of 1% for CFD positions held overnight. You can find detailed CFD financing rates here.

*Although we cannot liquidate non-CFD positions to cover a CFD deficit, we can liquidate CFD positions to cover a non-CFD deficit.

4 Incentives Offered to trade CFDs

The ESMA Decision imposes a ban on monetary and certain types of non-monetary benefits related to CFD trading. IBKR does not offer any bonus or other incentives to trade CFDs.