Electronic Order Matching
For most stock trades, the orders are routed into the appropriate stock exchange's electronic order system. If you placed a market buy order, the order will be quickly matched up with an order to sell at the ask price showing on your trade screen. The electronic stock exchange systems will notify your broker that the order has been filled. With a market order, on an actively traded stock, this process will take just a few seconds.
Your Account Summary Screen
When your trade to buy stock has been filled, the new shares will show up in your account summary screen as one of the investment positions in your account. This is where you can find the actual price at which the order filled. For most stocks, the order will fill at the ask price you saw on the order screen, but in a fast moving market, your price could be a few cents higher or lower.
Paying for the Shares
If you have the cash to pay for the stock in your account, the cost of the shares plus the broker's commission will be debited from your cash balance. Stock purchases have what is called T+3 settlement. You actually have three business days to pay for stock you have purchased. You can place a stock trade online and then wire the funds to your broker in the next couple of days. The stock trade does not become official until the third day after the trade was filled.
Shares Held by Broker
The stock shares will be held in electronic form by your broker for your brokerage account. The account summary will show whether the shares have gained or lost value since you made the purchase trade. If there is an event like a stock split, the broker will make the appropriate adjustments to the share position in your account. Dividends paid by the stock will go into the cash balance of your brokerage account.