Planning a trip to Spain for your upcoming vacation? Many travelers from the UK are still making a costly 600-euro error — and the Foreign, Commonwealth & Development Office has issued a caution to tourists prior to their departure. Every year, millions of Britons travel to Spain, but few are aware that hailing an unlicensed taxi can result in hefty fines. Rules regarding taxis vary by city in Spain, and getting into the wrong cab could drain your entire holiday budget.