Unless you are buying small "tourist art" from street vendors, most artwork requires an official export permit from the ( Registro Nacional de Bienes Culturales ).
If you forget your permit, some airports have a Registry specialist who can issue one for roughly 7 CUC per work . Top Places to Buy Art buying art in cuba 2017
State-owned galleries typically provide this permit and an official receipt at the time of purchase. Unless you are buying small "tourist art" from