Cuban Departure Tax
A Departure Tax of 25 CUC (equivalent to $25 USD) must be paid by every travellers with boarding passes, when leaving Cuba. Please note that babies are generally not required to pay the departure tax if they sit on parent's laps.
This tax has to be paid in CUC (Cuban Convertible Pesos), no other currency is accepted, and in CASH ONLY.
In every Cuban airport there are one or more "Departure Tax" windows near the check-in counters. This is where you pay the departure tax AFTER you've checked-in at your airline's check-in counter. They will affix a stamp on you boarding pass as a proof this tax has bee paid. Here's a picture of this stamp:
Cuban Departure Tax Stamp (real size: approximately 1½ X 1 inch)