| PO Number | Town / Place name | Code |
|---|---|---|
| 1 | Abbeyleix | |
| 2 | Adair | |
| Adare | ||
| 3 | Ahascragh | |
| Bunratty | ||
| 4 | Ardarra | |
| Cratloe | ||
| 5 | Ardee | |
| 6 | Ardglass | |
| Ardrahan | ||
| 7 | Ardrahan | |
| Abbeyfeale | ||
| 8 | Armagh | |
| 9 | Ballingarry | |
| 10 | Arklow | |
| 11 | Arthurstown | |
| Armoy | ||
| 12 | Arva | |
| Ashbourne | ||
| 13 | Ashbourne | |
| Aghadowey | ||
| 14 | Ashford | |
| 15 | Ashboy | |
| 16 | Athenry | |
| 17 | Athleague | |
| Ardsollus | ||
| 18 | Athlone | |
| 19 | Arva | |
| 20 | Athy | |
| 21 | Aughnacloy | |
| 22 | Aughrim, Gal | |
| Aughrim, Wick | ||
| 23 | Antrim | |
| 24 | Askeaton | |
| 25 | Bagnalstown | |
| Bagenalstown | ||
| 26 | Bailyborough | |
| Baily | ||
| 27 | Balbriggan | |
| 28 | Ballaghaderin | |
| 29 | Ballina | |
| 30 | Ballybay | |
| 31 | Ballinakill | |
| Ballimallard | ||
| 32 | Ballinasloe | |
| 33 | Ballincollig | |
| Ballybrack | ||
| 34 | Ballinderry | |
| Ballybofey | ||
| 35 | Ballingarry | |
| Ballycassidy | ||
| 36 | Ballinrobe | |
| Ballybrophy | ||
| 37 | Ballycastle | |
| Ballybunion | ||
| 38 | Ballyclare | |
| 39 | Ballyconnell | |
| Ballylongford | ||
| 40 | Ballybrittas | |
| Ballygawley | ||
| 41 | Ballygawley | |
| Ballycastle | ||
| 42 | Ballyglass | |
| Balla | ||
| 43 | Ballyhaise | |
| Ballyglunin | ||
| 44 | Ballyjamesduff | |
| Ballyhaunis | ||
| 45 | Ballymahon | |
| 46 | Ballymena | |
| 47 | Ballymoe | |
| 48 | Ballymoney | |
| 49 | Ballymore | |
| Ballymore Furnace | ||
| 50 | Ballymote | |
| 51 | Ballynacargy | |
| Ballymurry | ||
| 52 | Ballynahinch | |
| 53 | Ballynamore | |
| Baltinglass | ||
| 54 | Ballyragget | |
| 55 | Ballyshannon | |
| 56 | Ballytore | |
| 57 | Banagher | |
| 58 | Banbridge | |
| 59 | Bandon | |
| 60 | Bangor | |
| Barnesmore | ||
| 61 | Bantry | |
| 62 | Belfast | |
| 63 | Bellaghy | |
| Belleek | ||
| 64 | Belmullet | |
| Beauparc | ||
| 65 | Belturbet | |
| 66 | Broadford | |
| Bessbrook | ||
| 67 | Blackwatertown | |
| Blackrock | ||
| 68 | Blackrock | |
| Booterstown | ||
| 69 | Blessington | |
| 70 | Boyle | |
| 71 | Booterstown | |
| Borris | ||
| 72 | Bray | |
| 73 | Broadway | |
| Belfast and N. Counties R.P.O. | ||
| 74 | Brookeborough | |
| Belmullet | ||
| 75 | Broughshane | |
| Beragh | ||
| 76 | Bruff | |
| Bangor Erris | ||
| 77 | Buncrana | |
| Belmont | ||
| 78 | Bunratty | |
| Beaufort | ||
| 79 | Burrin | |
| Blarney | ||
| 80 | Borrisakane | |
| Bruree, Kilmallock | ||
| 81 | Borrisoleigh | |
| Brittas | ||
| 82 | Borris-in-Ossory | |
| 83 | Bushmills | |
| Bundoran | ||
| 84 | Buttevant | |
| 85 | Baltinglass | |
| Burton Port | ||
| 86 | Cabinteely | |
| Cabineteely | ||
| 87 | Cahirciveen | |
| 88 | Cahirconlish | |
| Rathdowney | ||
| 89 | Camp | |
| 90 | Cahir | |
| 91 | Caledon | |
| 92 | Caledon | |
| Caragh | ||
| 93 | Callan | |
| 94 | Camolin | |
| 95 | Cappoquin | |
| 96 | Carlingford | |
| Carbury | ||
| 97 | Carlow | |
| 98 | Carey's Cross | |
| 99 | Carns |