The methodology used to calculate the margin requirement for a given position is largely determined by the following three factors:

 

1.      The product type;

2.      The rules of the exchange on which the product is listed and/or the primary regulator of the carrying broker;

3.      IBKR’s “house” requirements.

 

While a number of methodologies exist, they tend to be categorized into one of two approaches: rules based or risk based.  Rules based methods generally assume uniform margin rates across like products, offer no inter-product offsets and consider derivative instruments in a manner similar to that of their underlying. In this sense, they offer ease of computation but oftentimes make assumptions which, while simple to execute, may overstate or understate the risk of an instrument relative to its historic performance. A common example of a rules based methodology is the U.S. based Reg. T requirement.

 

In contrast, risk based methodologies often seek to apply margin coverage reflective of the product’s past performance, recognize some inter-product offsets and seek to model the non-linear risk of derivative products using mathematical pricing models. These methodologies, while intuitive, involve computations which may not be easily replicable by the client. Moreover, to the extent that their inputs rely upon observed market behavior, may result in requirements that are subject to rapid and sizable fluctuation. Examples of risk based methodologies include TIMS and SPAN.

 

Regardless of whether the methodology is rules or risk based, most brokers will apply “house” margin requirements which serve to increase the statutory, or base, requirement in targeted instances where the broker’s view of exposure is greater than that which would satisfied solely by meeting that base requirement. An overview of the most common risk and rules based methodologies is provided below.

 

  

a.      Portfolio Margin (TIMS) – The Theoretical Intermarket Margin System, or TIMS, is a risk based methodology created by the Options Clearing Corporation (OCC) which computes the value of the portfolio given a series of hypothetical market scenarios where price changes are assumed and positions revalued. The methodology uses an option pricing model to revalue options and the OCC scenarios are augmented by a number of house scenarios which serve to capture additional risks such as extreme market moves, concentrated positions and shifts in option implied volatilities. In addition, there are certain securities (e.g., Pink Sheet, OTCBB and low cap) for which margin may not be extended. Once the projected portfolio values are determined at each scenario, the one which projects the greatest loss is the margin requirement.

 

Positions to which the TIMS methodology is eligible to be applied include U.S. stocks, ETFs, options, single stock futures and Non U.S. stocks and options which meet the SEC’s ready market test.

 

As this methodology uses a much more complex set of computations than one that is rules based, it tends to more accurately model risk and generally offers greater leverage. Given its ability to offer enhanced leverage and that the requirements fluctuate and may react quickly to changing market conditions, it is intended for sophisticated individuals and requires minimum equity of $110,000 to initiate and $100,000 to maintain. Requirements for stocks under this methodology generally range from 15% to 30% with the more favorable requirement applied to portfolios which contain a highly diversified group of stocks which have historically exhibited low volatility and which tend to employ option hedges.

 

b.       SPAN – Standard Portfolio Analysis of Risk, or SPAN, is a risk-based margin methodology created by the Chicago Mercantile Exchange (CME) that is designed for futures and future options.  Similar to TIMS, SPAN determines a margin requirement by calculating the value of the portfolio given a set of hypothetical market scenarios where underlying price changes and option implied volatilities are assumed to change. Again, IBKR will include in these assumptions house scenarios which account for extreme price moves along with the particular impact such moves may have upon deep out-of-the-money options. The scenario which projects the greatest loss becomes the margin requirement. A detailed overview of the SPAN margining system is provided in KB563.

 

a.      Reg. T – The U.S. central bank, the Federal Reserve Board, holds responsibility for maintaining the stability of the financial system and containing systemic risk that may arise in financial markets. It does this, in part, by governing the amount of credit that broker dealers may extend to customers who borrow money to buy securities on margin. 

 

This is accomplished through Regulation T, or Reg. T as it is commonly referred, which provides for establishment of a margin account and which imposes the initial margin requirement and payment rules on certain securities transactions. For example, on stock purchases, Reg. T currently requires an initial margin deposit by the client equal to 50% of the purchase value, allowing the broker to extend credit or finance the remaining 50%. For example, an account holder purchasing $1,000 worth of securities is required to deposit $500 and allowed to borrow $500 to hold those securities.

 

Reg. T only establishes the initial margin requirement and the maintenance requirement, the amount necessary to continue holding the position once initiated, is set by exchange rule (25% for stocks). Reg. T also does not establish margin requirements for securities options as this falls under the jurisdiction of the listing exchange’s rules which are subject to SEC approval.  Options held in a Reg.T account are also subject to a rules based methodology where short positions are treated like a stock equivalent and margin relief is provided for spread transactions. Finally, positions held in a qualifying portfolio margin account are exempt from the requirements of Reg. T.