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Published on Thursday, April 19, 2018  Modified on Monday, October 26, 2020
Strategy Level  Advance 
Instruments Traded  Call + Put 
Number of Positions  4 
Market View  Neutral 
Risk Profile  None 
Reward Profile  Limited 
Breakeven Point 
Short Box is an arbitrage strategy. It involves selling a Bull Call Spread (1 ITM and I OTM Call) together with the corresponding Bear Put Spread (1 ITM and 1 OTM Put), with both spreads having the same strike prices and expiration dates.
The short box strategy is opposite to Long Box (or Box Spread). It is used when the spreads are overpriced with respect to their combined expiration value.
This strategy is the combination of 2 spreads (4 trades) and the profit/loss calculated together as 1 trade. Note that the 'total cost of the box remain same' irrespective to the price movement of underlying security in any direction. The expiration value of the box spread is actually the difference between the strike prices of the options involved.
The usual box spread look like as below for NIFTY current index value as 10550 (NIFTY Spot Price):
Orders  NIFTY Strike Price  

Bull Call Spread  Sell 1 ITM Call  NIFTY18APR10400CE 
Buy 1 OTM Call  NIFTY18APR 10700CE  
Bear Put Spread  Sell 1 ITM Put  NIFTY18APR10700PE 
Buy 1 OTM Put  NIFTY18APR10400PE 
Note:
As you see in the above table, this is a delta neutral strategy. The trader is selling and buying equivalent spreads. As long as the price paid for the box is significantly higher than the combined expiration value of the spreads, a riskless profit can be earned. We will discuss this in detail in an example below.
As the profit from the short box is small. In many cases it is offset by the expenses i.e. brokerage and taxes. It's very important to consider the trading cost (brokerage, fee, taxes etc.) before trading in this strategy.
Being risks free arbitrage strategy, this strategy can earn better return than earnings in interest from fixed deposits for any investor. The earning from this strategy varies with the strike price chosen by the trader. i.e. Earning from strike price '10400, 10700' will be different from strike price combination of '9800,11000'.
The short box strategy should be used when the component spreads are overpriced in relation to their expiration values. In most cases, the trader has to hold the position till expiry to gain the benefits of the price difference.
Note: If the spreads are underpriced, another strategy named Long Box (or Box Spread) can be used for a profit.
This strategy should be used by advanced traders as the gains are minimal. The brokerage payable when implementing this strategy can take away all the profits. This strategy should only be implemented when the fees paid are lower than the expected profit.
Let's take a simple example of a stock trading at Rs 55 (spot price) in June. The option contracts for this stock are available at the following premium:
Lot size: 100 shares in 1 lot
Sell a Bull Call Spread = Sell 'July 50 call' + Buy 'July 60 call'
Bull Call Spread Cost = (Rs 7*100)  (Rs 1.5*100) = Rs 550
Sell Bear Put Spread = Sell 'July 60 put' + Buy 'July 50 put'
Bear Put Spread Cost = (Rs 7*100)  (Rs 2*100) = Rs 500
The total cost of the box spread is: Rs 500 + Rs 550 = Rs 1050
The expiration value of the box is computed to be: (Rs 60  Rs 50) x 100 = Rs 1000
Profit: Rs 1050  Rs 1000 = Rs 50
Net Profit = Rs 50  Brokerage  Taxes
In above example, since the total cost of the box spread is higher than its expiration value, a riskfree arbitrage is possible with the short box strategy. Now let's discuss about the possible scenarios:
Scenario 1: Stock price remain unchanged at Rs 55
The July 50 put and the July 60 call expire worthless while both the July 50 call and the July 60 put expires inthemoney with Rs 500 intrinsic value each. So the total value of the box at expiration is: Rs 500 + Rs 500 = Rs 1000.
Scenario 2: Stock price reaches to Rs 60
Only the July 50 call expires inthemoney with Rs 1000 in intrinsic value. So the box is still worth Rs 1000 at expiration.
Scenario 3: Stock price falls to Rs 50
A similar situation as scenario 2 happens but this time it is the July 60 put that expires inthemoney with Rs 1000 in intrinsic value while all the other options expire worthless. Still, the box is worth Rs 1000.
In all the possible scenarios, the box worth remains at Rs 1000 on expiry resulting in profit of Rs 50.
Let's take an example of NIFTY Options which is traded in lot size of 75.
Strike Price  Premium (Rs )  Premium Paid (Rs ) (Premium * Lot Size of 75)  
Bull Call Spread  Sell 1 ITM Call  10400  182.55  13691.25 
Buy 1 OTM Call  10700  20.35  1526.25  
Bear Put Spread  Sell 1 ITM Put  10700  174.00  13050.00 
Buy 1 OTM Put  10400  28.00  2100.00  
Total  23115.00 
Bull Call Spread Cost  =(13691.25+1526.25)  12165.00 
Bear Put Spread Cost  =(13050.00+2100.00)  10950.00 
Total Box Spread Cost  23115.00  
Expiration value of the box  =(1040010700)*75  22500.00 
Profit  =(23115.0022500.00)  615 
Brokerage + Taxes  =8 trades * Rs 20 + taxes  Rs 200 
Net Profit  Rs 415 (1.8%) 
Note the Net Profit changes when you buy options at different the strike price using the same strategy.
The market view for this strategy is neutral. The movement in underlying security doesn't affect the outcome (profit/loss). This arbitrage strategy is to earn small profits irrespective of the market movements in any direction.
Say for XYZ stock, the component spread is relatively overpriced than its underlying. You can execute execute Short Box strategy by selling 1 ITM Call and 1 ITM Put while buying 1 OTM Call and 1 OTM Put. There is no risk of loss while the profit potential would be the difference between two strike prices minus net premium.
The Short Box Spread Options Strategy is a relatively riskfree strategy. There is no risk in the overall position because the losses in one spread will be neutralized by the gains in the other spread.
The trades are also riskfree as they are executed on an exchange and therefore cleared and guaranteed by the exchange.
The small risks of this strategy include:
The reward in this strategy is the difference between the total cost of the box spread and its expiration value. Being an arbitrage strategy, the profits are very small.
It's an extremely lowrisk options trading strategy.
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