Postage Dues. 
Postage due stamps were first issued in 1925 and typographed by the Goverment Printers in Dublin Castle. Composed180 stamps in each sheet that were divided into three panes and guillotined into sub-sheets before sale, so no gutter pairs exist. Postage dues on commercial covers are sought after expecially in unusual uses and difficult rates.
For the first four yearsits independent existence, the Irish Post Office continued to use British postage-due stamps on underpaid items, which sometimes resulted in the creationunusual covers – Covers exist where someone in Ireland had sent “Saorstat Éireann” overprinted stamps to a correspondent in England for use on the reply; when these stamps were used, the British Post Office correctly considered the stamps to be invalid and raised a Taxe mark, thereby requiring the Irish Post Office to affix British postage due stamps to a cover which had the correct postage in Irish stamps!
In 1925 however, the Irish Post Office issued the first four valuesa simple design which was to form the basis for their postage due stamps for the next 55 years, comprising the text “postas le h’ioc/postage due” and the value in Irish: The initial values released on 20th February 1925, with the “se” watermark, were the 1d, 2d and 6d values, with the 1/2d released the following November. Following the change to the “e” watermark in 1940, the 2d value was released with the new watermark in 1940, followed by the 1d in 1941, the 1/2d in 1942, and new values5d on 03-03-1943, 3d on 10-11-1952, 1 1/2d in 1953, a reissuethe 6d on 21-03-1960, the 8d on 30-10-1962, 10d on 27-01-1965, and finally the shilling on 10-02-1969.
As in Britain, 15th February 1971 saw the conversion from pounds-shillings-pence currency to the decimal currency with pounds100 pence. Unlike Britain, which dropped the postage due design which had been running since 1914 in favoura modern new design, the Irish Post Office retained the same design as before and simply changed the coloursthe stamps: The 3p, 4p and 5p valuesthis series were reissued on 20.03.1978 without a watermark.
The mid to late 1970’s were a timehigh inflation in Ireland, and by 1980 the old series with a highest value8p was no longer adequate. On 11th June 1980, the 55-year old designs finally gave way to a new seriesdesigns, with the releasethe 1p, 2p, 4p, 6p, 8p, 18p, and 24p values, followed on 22nd August 1985 by the 20p, 30p and 50p.
On 6th October 1988 another new series was issued with a top value£1. This series was designed by the outside design studio “Q Design”.
Additional values: 20p, 30p and 50p were issued in 1985