You also get to trade in a chosen currency to simplify things further. The screenshot beneath is taken from my actual trading account at IG Index. You can see that I was trading using £ sterling even though I am betting on US indices.
Using the above example you can see at the bottom of the image that I had open positions on Wall Street, which is the Dow Jones Index. The contract had a March expiry which is actually on the 15th and was the 3rd Friday in March.
All spread bets just like a regular futures contracts must have an expiry date. However, should I wish to keep my bet open and not let it expire I can rollover my bet from March until June or even September.
Also in the above image you can see the open price of each position. So for example I have £10 a point position at 12752. A point on the Wall St index is 12752 to 12753, other markets may be 1/10 and sometimes even as low as 1/100th
The screenshot also displays the current price which is 13911.5. So this means the profit is the current price minus the entry price x £10 stake per point.
Of course if I had bet that the market was going to move down but it actually went up I’d of lost money. An interesting point to consider in this scenario is that if I use a stop loss I can limit my losses to say 100 points; but the potential upside profit far exceeds the downside.