Quote from lightrader:
Can you please elaborate on the adjustment issue? I really can't understand how you can separate the FX risk in this way when the stock collapses and the GBP/USD goes substantially up. In such situation I'm fine with losing on the stock itself but not with losing on the FX hedge in addition to losing on the stock.
The adjustment there refers to the way that, say if your stock pays a dividend (in gbp) then you will have to adjust the hedge to include that as well if your position is substantial. Or more accurately, as the value of the stock fluctuates then the amount of gbp to be hedged will change. But these are considerations if you have a very large position or you are a perfectionist, in any other case such actions won't justify the transactions costs.
FX risk vs stock risk:
OK so let's forget the IB account structure, pretend its another broker, and say you bought stock with a value of £10,000, and your account is denominated in USD. You are a natural long of GBP/USD. So your USD account balance will go up if the usd value of the stock goes up. That is either through the stock price rising, or the GBP/USD rate rising (with a £10k stock value in a usd account that will mean you gain/lose $1 for every pip).
A standard hedge would be to sell £10,000 GBP/USD at the same time as you buy the stock. Any p&l on this position will simply offset the FX risk on your stock trade.
I would like to show the payoffs in a grid but i don't know how to do that.
Scenario 1> Stock flat; GBP/USD rises:
The usd value of your stock rises.
This is offset by your FX hedge which shows an equal and opposite $move.
Scenario 2> Stock rises; GBP/USD flat:
The FX risk does nothing, the USD value of the stock rises - your account value rises.
Scenario 3> Stock falls; GBP/USD rises:
The FX risk is still eliminated. The rise in GBP/USD will have a positive effect on the USD value of your stock, which will be offset exactly by the hedge.
The stock value will fall, your account balance will fall, and it will be your own fault not the fault of fx.
On this short FX position i suspect you will have to pay a financing charge if you hold it for a long time, since you are borrowing gbp whichever way you look at it.