Finnish postcodes have five digits. The zeros in a value such as 00100 are part of the code. Store the postcode and postal locality separately before formatting them for display.
The example below illustrates field layout using a fictional street. It is not a verified mailing address.
Address layout example
00100 HELSINKI
FINLAND
| Field label | Meaning |
|---|---|
| Katuosoite | Street address |
| Postinumero | Postal code |
| Postitoimipaikka | Postal locality |
| Maa | Country |
What does 00100 becoming 100 tell me?
A step probably converted the postcode to a number. Inspect the submitted browser request, database value, API response and export to find where zeros first disappeared. Do not simply pad every short value: an input mistake and a type-conversion bug need different handling, and padding cannot verify an address.
How should JSON and spreadsheets store it?
Use a JSON string such as {"postalCode":"00100"}. Set a spreadsheet import column to text before importing. A five-digit number display format is not enough because the underlying value can still be numeric. Export and import the file again to verify that the zeros remain part of the field value.
What about city names and language?
Preserve the submitted city spelling as the display value and manage search aliases separately. Current fixtures include Helsinki, Espoo and Vantaa rather than all Finnish postal localities. Add manual Finnish-character input cases to check that the browser, storage layer and export encoding preserve the same text.
Regression checklist
- Keep 00100 as a string through input, API and export
- Set the postcode column to text when importing a spreadsheet
- Do not silently treat 100 as a verified equivalent of 00100
What the generator currently covers
Coverage is limited to three city options in Uusimaa. This is not a nationwide address directory or a replacement for Posti postcode lookup.
Try the Finland address generator