| Code | Name | Region |
|---|---|---|
| IECLA | Clara | |
| IECLC | Clarecastle | CE |
| IECMS | Claremorris | MO |
| IECLI | Clifden | |
| IECLG | Clogherhead | LH |
| IECRA | Carn | DL |
| IECDN | Carndonagh | DL |
| IEICK | Carrick | DL |
| IECAN | Carrickcarnan | |
| IECAS | Carrickmacross | |
| IECKM | Carrickmines | D |
| IECOS | Carrick-on-shannon | LM |
| IECRS | Carrick-on-suir | TA |
| IECAE | Carrigaline | CO |
| IECRR | Carrigans | DL |
| IECGO | Carrigtohill | CO |
| IEQSH | Cashel | |
| IECTR | Casteltownroche | CO |
| IECLB | Castlebar | |
| IECAM | Castlebellingham | |
| IECBY | Castleblaney | |
| IECAT | Castlecomer | KK |
| IECAL | Castleconnell | |
| IE7CM | Castledermot | KE |
| IECFI | Castlefinn | |
| IEBRA | Bray | WW |
| IEBRE | Bree | WX |
| IEBGE | Bridge End | DL |
| IEEBF | Broadford | CW |
| IEBRU | Bruree | LK |
| IEBUN | Bunbeg | DL |
| IEBUY | Bunclody | WX |
| IEBUC | Buncrana | |
| IEBRT | Bunratty | CE |
| IEBFO | Burnfoot | |
| IEBUR | Burtonport | |
| IEBUT | Butlerstown | CO |
| IECHR | Caher | |
| IECAI | Cahir (an Chathair) | |
| IECHE | Cahirciveen | |
| IELLN | Callan | KK |
| IECML | Camolin | WX |
| IECAP | Cappoquin | WD |
| IECAR | Carlingford | |
| IECAW | Carlow | |
| IEBES | Bangor Erris | MO |
| IEBYT | Bantry | CO |
| IEBTH | Bantry Harbour | CO |
| IEBWD | Bawnboy | CN |
| IEBEF | Belfast |