If not at the electrical panel it could be at the meter.
You could also have what is known as a split bus panel. There is not one main breaker. The panel has double pole 240 volt breakers in the top half. One of them turns off the bottom half of the panel. You need to turn off all the double poles in the top half to shut off the entire house.
Do not PM with questions that can be asked in a forum. I will not respond.