Before 1857 the Church of Ireland, as the Established Church, had charge of all testamentary affairs. Consistorial Courts in each diocese were responsible for granting probate, that is, for legally authenticating a will and conferring on the executors the power to administer the estate. The courts also had the power to issue letters of administration to the next of kin or the main creditor on the estates of those who died intestate. Each court was responsible for wills and administrations in its own diocese. However, when the estate included property worth more than £5 in another diocese, responsibility for the will or administration passed to the Prerogative Court, under the authority of the Archbishop of Armagh.
The wills and administration records of the Consistorial Courts were held locally in each diocese, sometimes in very poor environments, up to the abolition of the testamentary authority of the Church of Ireland in 1857. After that date the Public Record Office of Ireland began the slow process of collecting the original records and transcribing them into Will and Grant Books. The Office then indexed the wills and administration bonds (the sureties the administrators had to produce as a guarantee that the estate would be properly administered). None of the Consistorial Courts had records of all the wills or administrations they had dealt with. Very little earlier than the seventeenth century emerged, and the majority of the courts appear to have had serious gaps before the middle of the eighteenth century. All the original wills and administrations in the Public Record Office were destroyed in 1922, along with almost all the Will and Grant Books into which they had been transcribed. The only exceptions are the Will Books for Down (1850-58) and Connor (1818-1820, 1853-8) - online at genealogy.nationalarchives.ie - and the Grant Books for Cashel (1840-45), Derry and Raphoe (1812-51) and Ossory (1848-58), which are only available in NAI.
The indexes to wills and administration bonds were not destroyed, although a number were badly damaged. The wills indexes are alphabetical and normally give the testator's address and the year of probate as well as occasionally specifying his occupation. The administration bonds indexes are not fully alphabetical, being arranged year by year under the initial letter of the surname of the deceased person. They give the year of the bond, the full name and usually the address of the deceased, and sometimes their occupation. Many of the wills indexes have been published or made available online, and details of these will be found on this site.
To recap: an estate was dealt with by the Prerogative Court, rather than a Consistorial Court, if it covered property worth more than £5 in a second diocese. In general, then, prerogative wills and administrations tend to cover the wealthier classes, merchants with dealings in more than one area, and those who lived close to diocesan borders. Up to 1816 the Prerogative Court was not housed in a single place, with hearings generally held in the residence of the presiding judge. From 1816 the King's Inns building in Henrietta Street, Dublin, provided a permanent home. For this reason the records of the court before 1816 cannot be taken as complete. After 1857 all these records were transferred to the Public Record Office, where the original wills and grants of administration were transcribed into Prerogative Will and Grant Books and indexed. The indexes survived 1922, frustratingly, but all the original wills and grants, and almost all the Will and Grant Books, were destroyed. Details of those books and indexes that survived will be found on this site.
The loss of the original prerogative wills is mitigated to a large extent by the project carried out in the early decades of the nineteenth century by Sir William Betham, Ulster King of Arms. As well as preparing the first index of testators, up to 1810, he also made abstracts of the family information contained in almost all the wills before 1800. The original notebooks in which he recorded the information are now in the National Archives of Ireland, and the Genealogical Office has his sketch pedigrees based on these abstracts and including later additions and amendments. PRONI has a copy of the Genealogical Office series made by a successor of Betham's, Sir John Burke (T559), but without the additions and amendments. Betham also made a large number of abstracts from prerogative grants up to 1802. The original notebooks for these are also in NAI. The Genealogical Office transcript copy (GO 257-60) is fully alphabetical, unlike the notebooks. About half of the GO manuscripts are digititised in NLI's catalogue. A listing is here.
The first index to prerogative wills, up to 1810, was published in 1897 by Sir Arthur Vicars, Burke's successor as Ulster King of Arms, as Index to the Prerogative Wills of Ireland (1536-1810), and can be used as a guide to Betham's abstracts and sketch pedigrees, with the proviso that wills from the decade 1800-1810 are not covered by Betham. The book is widely available online, including at
www.archive.org. The copy at FindMyPast includes a 1914 supplement with more than 1200 corrections and insertions. The manuscript index for the period 1811-57 is in the NAI reading room and online (see here). As with the consistorial administration bonds indexes, the prerogative grants indexes are not fully alphabetical but are simply arranged year by year under the initial letter of the surname of the deceased person.