| PO Number | Town / Place name | Code |
|---|---|---|
| 300 | Leighlinbridge | |
| Laurencetown | ||
| 301 | Leixlip | |
| Leggs | ||
| 302 | Letterkenny | |
| 303 | Limerick | |
| 304 | Lisburn | |
| 305 | Lismore | |
| 306 | Lisnakea | |
| 307 | Listowel | |
| 308 | Littleton | |
| Lixnaw | ||
| 309 | Longford | |
| 310 | Loughbrickland | |
| Loughlinstown | ||
| Shankill | ||
| 311 | Loughgall | |
| Lough Eske | ||
| 312 | Loughrea | |
| 313 | Lowtherstown | |
| Lispole | ||
| 314 | Louth | |
| Lucan | ||
| 315 | Lucan | |
| Lahinch | ||
| 316 | Lurgan | |
| 317 | Macroom | |
| Lusk | ||
| 318 | Maghera | |
| Mageney | ||
| 319 | Magherafelt | |
| 320 | Malahide | |
| 321 | Mallow | |
| 322 | Manorhamilton | |
| Manorcunningham | ||
| 323 | Markethill | |
| Magheramena | ||
| 324 | Maryborough | |
| 325 | Maynooth | |
| Maghera | ||
| 326 | Middleton | |
| Midleton | ||
| 327 | Millstreet | |
| Markethill | ||
| 328 | Miltown | |
| Milltown | ||
| 329 | Miltown Malby | |
| 330 | Mitchelstown | |
| 331 | Moate | |
| 332 | Mohill | |
| Moira | ||
| 333 | Moira | |
| Moyvore | ||
| 334 | Monaghan | |
| 335 | Monastrevan | |
| 336 | Moneygall | |
| Monkstown | ||
| 337 | Moneymore | |
| 338 | Mountmellick | |
| 339 | Mount Nugent | |
| Mount Pleasant | ||
| 340 | Mountrath | |
| 341 | Mount Talbot | |
| Multyfarnham | ||
| 342 | Moville | |
| Muckamore | ||
| 343 | Moy | |
| 344 | Moynalty | |
| Mulhuddart | ||
| 345 | Mullingar | |
| 346 | Naas | |
| 347 | Narin | |
| 348 | Navan | |
| 349 | Nenagh | |
| 350 | New Birmingham | |
| 351 | Newbliss | |
| 352 | Newbridge | |
| 353 | Newcastle | |
| Newcastle West | ||
| 354 | Newmarket on Fergus | |
| 355 | Newport (Mayo) | |
| 356 | Newport (Tip) | |
| 357 | Newry | |
| 358 | Newtonards | |
| 359 | Newtownbarry | |
| Newtonforbes | ||
| 360 | Newtownforbes | |
| 361 | Newtownhamilton | |
| 362 | Newtown Limavady | |
| 363 | Limavady | |
| 364 | Newtownmountkennedy | |
| 365 | Newtown Stewart | |
| 366 | Oldcastle | |
| 367 | Omagh | |
| 368 | Oranmore | |
| 369 | Pallasgreen | |
| 370 | Pallaskenry | |
| 371 | Parsonstown | |
| Birr | ||
| 372 | Passage West | |
| Philipstown | ||
| 373 | Philipstown | |
| Pettigo | ||
| 374 | Piltown | |
| 375 | Portadown | |
| 376 | Portaferry | |
| Pomeroy | ||
| 377 | Portarlington | |
| 378 | Portglenone | |
| Patrickswell | ||
| 379 | Portlaw | |
| 380 | Portumna | |
| Portrush | ||
| 381 | Ramelton | |
| Portrush | ||
| 382 | Randalstown | |
| 383 | Raphoe | |
| 384 | Rathagan | |
| Ratheney | ||
| 385 | Rathcoole | |
| Portglenone | ||
| 386 | Rathcormack | |
| Rathcoole | ||
| 387 | Rathdowney | |
| 388 | Rathdrum | |
| 389 | Rathfarnham | |
| 390 | Rathfriland | |
| 391 | Rathkeale | |
| 392 | Rathowen | |
| Rathnew | ||
| 393 | Red Hills | |
| Ratoath | ||
| 394 | Rich Hill | |
| Rockcorry | ||
| 395 | Rochfort Bridge | |
| Roundstone | ||
| 396 | Roscommon | |
| 397 | Roscnea | |
| 398 | Ross | |
| New Ross | ||
| 399 | Rosscarbery |