In order to prove you have been non-resident for a period of time you will have to supply Revenue with evidence of all your day to day living costs, eg. utility bills for services abroad, receipts for car hire, petrol, payslips with your foreign address, visa card and bank statements relating to your time abroad and if it is a country where you need a residence permit after a certain period then that would be useful too. I imported a car from Spain a while back and these are the items I was asked for as evidence of my non-residency status so that I was allowed to re-register the car here in Ireland without having to pay VRT. I was out of Ireland for 18 months.