A significant proportion of all births, marriages, and deaths were simply not registered, as mentioned above. When the individuals concerned, or their relatives, later needed a certificate for official purposes, it became necessary to register the event. The index references for these late registrations are included in the volume for the year in which the event took place. Therefore, for example, the index reference for someone born in 1880 but whose birth was not registered until 1900 is to be found in the index for 1880. In the case of births and deaths these references are indexed separately from the main body of the index, at the back of the volume. For marriages, late registrations are written in by hand at the relevant point in the main body of the index. Although the chances of finding a missing registration among these are quite slim, it is still necessary to include them in any thorough search of the Indexes. The fresh indexes created by the GRO and now at IrishGenealogy.ie include all these late registrations. The transcripts of the printed indexes at FamilySearch.org include some but not all late registrations.
From 1864 up to the present, the GRO has kept a separate 'Marine Register' of births and deaths of Irish subjects that took place at sea. There are 12,382 records between 1864 and 1922. From 1886 only, a printed index to this register is bound into the back of the births and deaths index for each year. For earlier registers the indexes are in GRO headquarters in Roscommon and have to be requested from there. No separate register was kept for marriages at sea. The LDS copy is on film 101765.
The 'Births, Deaths and Marriages (Army) Act' of 1879 required these events to be registered with the Office of the Registrar-General in Dublin, where they affected Irish subjects serving in the British army abroad. There are 15,436 registrations recorded between 1883 and 1922. Separate indexes, bound into the backs of the main yearly indexes, start from 1888 and continue until 1930 for births and until 1931 for marriages and deaths. The deaths index for 1902 also contains an index to 'Deaths of Irish Subjects pertaining to the South African War (1898-1902)'. There is also a separate register of deaths of 'Irish NCOs and men who died in the Great War', with 28,044 entries.
From 1864, the GRO was required to keep a separate register of births, marriages and deaths of Irish subjects abroad, where such births were notified to the relevant British consul. There is no index to this register, which contains only 208 entries. It is held in GRO headquarters in Roscommon. The LDS copy is on film 101764.
The GRO also holds the 'General Index to Baptisms and Marriages purported to have been celebrated by the Rev, J.F.G. Schulze 1806-1837'. Schulze was one of a group of eleven Dublin clergymen, known with characteristic Dublin bluntness as 'couple-beggars' or 'tack 'ems', who specialised in clandestine marriages between 1799 and 1844. The records of the other ten were destroyed in the Public Record Office in 1922, but a court challenge in the 1870s resulted in Schulze's marriages being declared legally sound, and two volumes of his records were acquired by the GRO. They record 55 baptisms and c.14,000 marriages . Most of the marriages, celebrated at the German Lutheran Church in Poolbeg Street, Dublin, are for the years 1825-37, and record only the names of the contracting parties. The original is held in GRO headquarters in Roscommon. The LDS copy is on film 101771. An indexed copy of the register was published in 2015 as Irregular Marriages in Dublin Before 1837 (ed. Harry McDowell, Dundalk, Dún Dealgan Press).