According to the Ibiza Airport website, there are four Ibiza rent a car companies
They are all at the airport terminal (on floor 0) and all four companies maintain operating hours of 7am to 11pm.
In Spain, and for the Ibiza rent a car companies above, the minimum age may vary by company. Underage fees will depend on the policy of the rental car company you choose and sometimes on what vehicle type/size you rent. (I could find no max age restrictions).
If you are looking to take your rental car outside of Spain, make sure to check with your preferred car rental company about any possible geographic restrictions.
Generally, vehicles that are rented in Spain are not allowed to be driven into Albania, Bosnia, Belarus, Bulgaria, Czech Republic, Croatia, Estonia, Greece, Hungary, Latvia, Lithuania, Macedonia, Montenegro, Poland, Russia, Slovakia, Slovenia, Turkey, Ukraine and Yugoslavia.
Some companies may offer the ability to drive into restricted countries, with certain vehicle types for an extra fee, but this is not common. Make sure to check policies with your specific rental provider.
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