Seeduwa Postal Code
| City | Postal Code | District |
|---|---|---|
| Katunayake IPZ | 11420 | Gampaha |
| Katunayake Air Force Camp | 11440 | Gampaha |
| Katunayake | 11450 | Gampaha |
| Negambo | 11500 | Gampaha |
| Talahena | 11504 | Gampaha |
| Kimbulapitiya | 11522 | Gampaha |
| Dagonna | 11524 | Gampaha |
| Katuwellegama | 11526 | Gampaha |
| Thimbirigaskatuwa | 11532 | Gampaha |
| Katana | 11534 | Gampaha |
| Akaragama | 11536 | Gampaha |
| Badalgama | 11538 | Gampaha |
| Kochchikade | 11540 | Gampaha |
| Minuwangoda | 11550 | Gampaha |
| Andiambalama | 11558 | Gampaha |