Read your broker agreement. Is there a clause that states your broker is entitled to a commission for X number of months after the agreement expires? If you found the buyer, that's fine, BUT don't sell or close the sale until after the broker agreement expires (after X number of months stated in the agreement.). Every real estate sale gets recorded in the county records and any agent can check the county records to get the names of the seller and buyer + the date the home was sold. If your agent finds out you sold your home before the broker agreement ended, yes you will owe the full commission.