These expired in the UK, Austria, Belgium, France, Germany, Luxembourg, Malta, Spain and the Netherlands on January 1.
Romanian and Bulgarian nationals are now free to live and work in the UK and are no longer required to obtain prior authorisation from the Home Office. Previously they had to obtain evidence of permission to work or of their right to reside as a worker, which was only granted in certain circumstances, such as for students, the self-employed or for certain jobs.
As EU citizens, Romanian and Bulgarian nationals can claim benefits and are entitled to NHS care. But like other EU migrants - and British nationals returning after living abroad - they will be affected by new tighter rules which came into effect on January 1, which mean they have to be resident in the UK for three months before claiming Jobseeker's Allowance.
Out-of-work benefits for EU migrants may also be cut after six months unless they can provide "compelling evidence that they have a genuine prospect of work", according to advice on the UK Border Agency website.
Other changes introduced include deporting EU migrants found begging or sleeping on the streets and banning them from re-entering the UK for a year, unless they get a job. The UK Government has also outlined plans to stop housing benefits for new EU migrants over the next year.
Estimates of the numbers of Romanians and Bulgarians heading to the UK vary hugely. Migration Watch, which campaigns for tighter controls on immigration, says 50,000 will move to the UK each year for five years.
But the Migration Matters Trust - which is campaigning for "an open and honest debate about the issues of migration" - says it believes levels are likely to be in the "low tens of thousands", rather than the "hundreds of thousands some people have been claiming".