Postal codes

File: data/postal-codes.json. The 1149 Belgian postal codes, each linked to the municipality it belongs to by REFNIS code: 1152 records, because 3 postal codes belong to two municipalities.

Why it's useful

• From an address to the judicial map. Addresses come with a postal code, not a REFNIS code. The postal code gives the municipality, and the municipality gives its cantons and courts: findCourtsForPostalCode('9050', 'labour-court') answers "which court for this address?" as far as the postal code can.
• The postal codes of a municipality. Validating a form, addressing a mailing, checking that an address and a REFNIS code agree: getPostalCodes('44021').
• The municipality of every court, prison and house of justice. Their address.municipality is this link, applied to the postal code of the published address (#28).

Source and updates

Source	Statbel's conversion table from postal codes to REFNIS codes, the table valid from 1 January 2025 (…_va01012025.xlsx)
Built by	scripts/parse/postal-codes.ts from the weekly snapshots. The build fails when a code points at a REFNIS code that isn't in municipalities.json, or a municipality has no code
Changes when	Statbel publishes a new table: municipalities merge, bpost adds or retires a postal code
Covers	1 January 2025 onwards: lookups for an earlier day throw a RangeError (time). A later table gives the pairs it drops a validTo and the pairs it adds a validFrom, on the day the table applies
Checked	Every week, by the sources workflow
Licence	© Statbel, CC BY 4.0

Statbel builds the table from bpost's postal offices and the municipalities of the FPS Finance. It also carries a municipality name per row, which isn't stored here: it differs from Statbel's own REFNIS list in a few places (Tongeren-Borgloon where the list says Tongres-Looz, and Saint-Nicolas for Sint-Niklaas), and a record links to its municipality rather than copy it. getMunicipality(record.municipality).name has the names.

Shared postal codes

A municipality has several postal codes (Gent has ten), and a postal code belongs to one municipality, with three exceptions:

Postal code	Municipalities
1040	Brussel (21004) and Etterbeek (21005)
1050	Brussel (21004) and Elsene (21009)
1804	Vilvoorde (23088) and Zemst (23096): Cargovil

For these, the street decides. getMunicipalitiesForPostalCode returns both municipalities, and findCourtsForPostalCode answers per municipality, so a shared code is never silently resolved to one of them.

Fields

Field	Type	Description
id	PostalCodeId	The postal code and the REFNIS code, joined: 9000-44021. Neither alone names a record; together they're both official and unique. See identifiers
validFrom, validTo	string?	The days the pair applies, as Statbel's tables give them; none: since the coverage starts, or still applies. See time
postalCode	string	The four-digit postal code
municipality	MunicipalityId	The municipality the postal code belongs to, by REFNIS code

interface PostalCode {
    id: PostalCodeId // '9000-44021'
    validFrom?: string
    validTo?: string
    postalCode: string // '9000'
    municipality: MunicipalityId // '44021'
}

What isn't in it

• Sub-municipalities (deelgemeenten, sections de commune): Statbel's table stops at the municipality. bpost's own postal-code list names the localities, but carries no REFNIS code and is published under bpost's terms of use (all rights reserved), not an open licence, so it isn't used.
• The street. In a city split over cantons (Antwerpen, Gent, Brussel, Luik, …) the postal code gives the municipality, and the municipality gives several cantons. The street then decides: with the address's coordinates, findCantonsAt finds the canton in the canton boundaries.

Helpers

Each is described, with its results and errors, in the API reference.

import { getMunicipalitiesForPostalCode, getPostalCodes } from 'belgica/postal-codes'
import { findCourtsForPostalCode } from 'belgica'

getMunicipalitiesForPostalCode('9050').map((m) => m.name.nl) // ['Gent']
getMunicipalitiesForPostalCode('1040').map((m) => m.name.nl) // ['Brussel', 'Etterbeek']
getPostalCodes('44021').map((p) => p.postalCode) // ['9000', '9030', '9031', …]

// Per municipality: its justices of the peace, and its courts of the type asked for
findCourtsForPostalCode('9050', 'labour-court')
// [{ municipality: Gent, justicesOfThePeace: [gent-1 … gent-5], courts: [labour-court-gent] }]