Prior to Irish independence in 1922 Ireland was part of the UK. In 1922 Ireland was split along the lines of partition into Northern Ireland, which continued to be a part of the UK; and the Irish Free State, which became largely independent. Paper money in Ireland had been provided by six of the nine Joint Stock banks which had the right to issue banknotes which, though not Legal Tender, were exchangeable at par with the British Pound Sterling.
Partition of the country lead to the question of a currency for use within the Irish Free State.
The Legal Tender Notes were introduced on 10 September 1928. Shortly thereafter, on 6 May 1929, the extant circulating Old notes of the banks were withdrawn and the note issues of the banks were split between the Northern Ireland Issue and the Consolidated Bank Note issue.
Of the extant Old notes (Pre-partition all-Ireland issues) in circulation, the notes apportioned to Northern Ireland (22% of the issues) were to be replaced by a Northern Ireland issue, and notes apportioned to the Irish Free State (78%) were replaced by the new Consolidated Bank Note issue.