1980s ITV sitcom starring Keith Barron and Gwen Taylor as holidaymakers David and Amy Pearce (4-4)
I believe the answer is:
duty-free
(Other definitions for duty-free that I've seen before include "Goods exempt from tax" , "With exemption from customs tax" , "Not subject to tax, as at airports" , "Carrying no import/export tax" , "Exempt from import levy" .)