| Province | Postal Code | Area Code | ISO Code |
| Ilocos Norte | 2900 | 77 | PH-ILN |
| Ilocos Sur | 2700 | 77 | PH-ILS |
| La Union | 2500 | 72 | PH-LU |
| Pangasinan | 2400 | 75 | PH-PG |
| Province | Postal Code | Area Code | ISO Code |
| Ilocos Norte | 2900 | 77 | PH-ILN |
| Ilocos Sur | 2700 | 77 | PH-ILS |
| La Union | 2500 | 72 | PH-LU |
| Pangasinan | 2400 | 75 | PH-PG |