When an order does not execute at the price that you place an order, it could be for the following reasons -

• The price you placed the order at is Higher than the current price (for sell orders) or Lower than the current price (for buy orders)
• The quantity you need is not available at that price

Orders are executed on a first come first serve basis when there is a matching price and quantity available in the Order book. If you are placing a buy order at the current market price, there should be a sell order in the order book at the same or lower price and the sell quantity should be equal to or greater than your buy quantity. This will fully execute your order. If the quantity available is lower, it will partially execute your order.

Similarly, if you are placing a sell order at the current market price, there should be a buy order in the order book at the same or higher price and the buy quantity should be equal to or greater than your sell quantity. This will fully execute your order. If the quantity available is lower, it will partially execute your order.