# Derived postcode places

Derived postcode places are the towns and centroids a national address register adds to a country's postcode directory as it compiles — beside the directory's own rows, never in their place.

Date: 2026-09-17

Derived postcode places are what a national address register contributes to a country's postcode directory as it is compiled: for every postcode the register's buildings carry, the towns those buildings are written with and the mean of their positions, added to the directory beside what the directory already lists.

## What Spaw answers

Ten registers declare it — Switzerland, Austria, Czechia, Norway, the three Belgian regions, Luxembourg, Australia and Latvia — and after each compiles, codes the directory lacks are inserted under the register's own `-postcodes` dataset, and codes it holds gain the register's places after their own and a centroid only where they had none. `locality_matches_postcode` then knows every town a register writes under a code, not only the operator's default one, and `postcode_status: live` answers for codes the postal-code dump never carried. The weekly places sync re-applies it after the dump's own replace.

## What it does not mean

It does not make a directory complete, and it does not replace one. A register of buildings never lists box-only and large-recipient codes — Swiss and Austrian Postfach codes, Australian GPO boxes, Czech special codes — so replacing the directory would have turned real box addresses into `postcode_not_found`; coverage moves to complete only when the operator's published total is configured and the union reaches it, and no country's total is configured yet. The United States gets its extra places from a different source, the Census Bureau's ZCTA-to-place file, and stays unscored on a town mismatch because that file lists places whose land a ZIP touches, not the names the postal service accepts.

Reference: https://spaw.co/glossary/derived-postcode-places