When you place an order, we give an indicative price based on the current market data we have available to us at the time. When we execute your order you may find the actual price you need to pay may be different.
This could be for a number of reasons, but the most common is that the live price, taken from the market, reflects the ‘mid price’ of the stock. This is similar to the difference between the FX rate you might see on the news and the rate you can get if you go to buy the currency at a bureau de change. Stocks rarely trade at the mid price, unless you are trading extremely large quantities. When executing your order, we take quotes from multiple sources to ensure that we get the best price possible for you.
Prices constantly change, especially during periods of market volatility.