As the title says, it's a strange question. I understand that you can send an order through your broker asking to buy/sell as many shares at a time, but what I'm wondering is how it gets filled at the exchanges. If you send a buy order for 1000 shares of stock XYZ at $50.00 to the exchanges and there's only 300 shares at that price left, what happens? Another scenario: What would happen if 10 people all sent the same price for 100 shares each, but there was only 500 shares of that stock, who would get it?