Of all the disruptions covered by EC261, denied boarding is in many ways the most clear-cut. When an airline sells more seats than exist on the aircraft and you are the one left standing at the gate, there is very little ambiguity about who is responsible. The airline made a deliberate commercial decision to overbook, and you are paying the price. EC261 reflects this by providing strong, immediate rights.
Voluntary vs involuntary denied boarding
Airlines that overbook will usually first ask for volunteers willing to give up their seats in exchange for benefits, typically a later flight plus a voucher or cash incentive. If you volunteer, you negotiate directly with the airline and the EC261 compensation rules do not apply; you accept whatever deal is offered.
Involuntary denied boarding is different. If not enough people volunteer and you are bumped against your will despite having a valid ticket, confirmed reservation, and having checked in on time, the airline must pay you the full EC261 compensation amount immediately. This is not subject to the extraordinary circumstances defence — overbooking is always the airline's decision, never an unforeseeable event.
No extraordinary circumstances defence
Unlike delays and cancellations, airlines cannot invoke extraordinary circumstances to avoid paying denied boarding compensation. Overbooking is a deliberate commercial practice, and the airline bears full responsibility.
What you're entitled to
If you are involuntarily denied boarding, EC261 entitles you to all of the following (not just one or the other, but all simultaneously):
Compensation: The same distance-based amounts as for cancellations: €250, €400, or €600 depending on the route. The airline must pay this immediately, at the airport, before you leave the check-in area. In practice, many airlines issue it later, but you are legally entitled to immediate payment.
Choice of refund or rebooking: The same three options as for cancellations: full refund, rebooking at the earliest opportunity, or rebooking at a later date of your choosing.
Right to care: Meals, refreshments, hotel accommodation if necessary, and communications while you wait for your alternative flight.
Check-in deadlines matter
Your right to denied boarding compensation depends on having checked in on time. Each airline sets its own check-in deadline, and if you arrive after it, the airline can refuse to board you without owing compensation. This applies to both online check-in deadlines and airport check-in counter closing times.
If you checked in on time (and can prove it; keep your confirmation email or check-in screenshot), the airline cannot use late arrival as a reason to deny your claim.
Other reasons for denied boarding
Not every refusal to board constitutes "denied boarding" under EC261. The regulation does not apply if you were refused boarding for legitimate reasons such as health or safety concerns, inadequate travel documents (wrong passport, missing visa), or disruptive behaviour. In these cases, the airline is acting on legal or safety grounds, not for its own commercial convenience.
However, if the airline claims a reason that seems pretextual, for example citing vague "security concerns" when the real reason appears to be overbooking, you have the right to challenge this and should document everything carefully.