Departure tax

A departure tax is a fee charged (under various names) by a country when a person is leaving the country.

Some countries charge a departure tax only when a person is leaving by air. Various rules apply to the payment of the tax, including payment at the airport to those about to catch a flight (sometimes only in the local currency and sometimes by credit card), or by some prepayment method, or it may be charged to the airlines and included in the airline ticket price.

...
Wikipedia