News and advice about overbooking appears with some regularity, but the correspondence we receive indicates many passengers are not aware of what airlines must provide when they’re involuntarily bumped. Please note that I’m not talking about what happens when you volunteer to take a later flight, which is between you and the airline and usually results in a voucher worth an agreed-upon amount (make sure you know what the voucher’s restrictions are before you agree to the deal).

I’m also referring to denied boarding due to overbooking, not because of something outside an airline’s control—e.g., a smaller aircraft must be substituted because of a mechanical issue, or an inbound plane is grounded in another city due to air traffic control. In such cases, if you are denied boarding, it’s as if your flight was cancelled due to weather; the airline does not owe you compensation.

Now that we’ve got that straight, what are the compensation rules? On a domestic flight, it depends on when the new flights are scheduled to arrive at your final destination.

• If it’s within one hour of your original arrival time, no compensation is due.

• If it’s between one and two hours (one and four hours for international flights), the airline must pay 200 percent of your one-way fare to your final destination, with a $650 maximum.

• If it’s more than two hours (four hours for international flights), or if the airline does not offer alternate flights, the compensation is 400 percent of your one-way fare, with a $1300 maximum.

• If there’s no fare on your ticket (for instance, mileage bookings), compensation is based on the lowest fare paid for a ticket in the same class of service on the overbooked flight.

That’s a brief overview. Read the rules at the DOT Fly-Rights page for all conditions and exceptions. To know what airlines have to do if you’re bumped because a plane is too heavy, read my column from July 18.

Rules also vary in different locations. In the EU, for example, the amounts range from €250 to €600 (currently $329 to $789) and are based on flight distance. Go to the EU Denied-Boarding Compensation System EU Denied-Boarding Compensation System page for its conditions and exceptions. In many countries, there are no set amounts and the airline’s own conditions of carriage outline the policies and compensation (sometimes it’s zip).

Even if you are due real money, the airline may offer you a voucher instead. If you don’t want it, you have the right to demand payment in currency. Getting bumped can be a big hassle, so if you’re going to arrive late to your destination as a result, remember you might be able to get there with extra cash in your pocket.