Get either permanent or temporary export certificate from Police dept in UAE from emirate where vehicle is registered. If permanent export and car is less than two years old get import duty document from Customs Finance dept in UAE. Drive or ship via land. At Qatar border pay 5% of car value if older than two years for permanent import. Pay clearing fees. If permanent import register vehicle at border. Total cost around QR5-10,000 depending on age of car and temporary or permanent export and shipping method (self-drive / shipping via truck). Also, some clearing fees payable in Saudi. I have brought in a motorbike and a car and it is a lot of expense, time and trouble. My advice - don't bother unless you have an expensive car and can't sell it in the UAE! Good luck.