You must bring all the following documents to the department or Foreign Affairs in Dublin and the Irish Embassy in London. They will check them all and then they will contact the Irish Consulate in Rome, which will issue the Nulla Osta.

The processing of the documents takes time you must submit your application in time, but not earlier than six months before the wedding date:

• Completed Questionnaire (MP1) 


• Completed Statutory Declaration (MP2)

• Original Long form of civil birth certificate


• Copy of Passport


• Court Order if you are under 18 years


• Death Certificate of previous spouse if widowed


• Petition and Final decree of divorce: if divorced


• Fee for Nulla Osta which may vary from year to year

All documents in languages other than English should be translated and if not in original photocopies should be authenticated.

http://www.dfa.ie/home/index.aspx?id=274