# Unit check

The unit check reads the flat or suite written on an address against the units a national register lists at the building: ok, missing, unexpected or null. Two of those are risk signals.

Date: 2026-09-17

The unit check is what the flat, apartment or suite written on an address says against the units a national register lists at the building it was followed to — nothing written at a building with several units, a suite written at a single residence, or the two agreeing — and it is answered only where a register found the building and declares its units.

## What Spaw answers

`unit_check` reads `ok`, `missing`, `unexpected` or null. `missing` — the register lists several units and none was written — carries the `unit_missing` signal at 20, because post for a block of flats with no flat number is the delivery-point problem the postal services sell an answer to. `unexpected` — a flat or suite written at a building the register lists as a single residence — carries `unit_unexpected` at 30, the classic invented-suite tell. Null means the register did not find the building, does not say how many units it has, or lists one unit at a building whose use is not residential, where a suite is ordinary; a private-mailbox number ("PMB 5") is a box, not a flat, and never counts as a unit here.

## Which registers can say

Only a register that publishes its units: the Austrian register counts dwellings per building, the Belgian one carries box numbers, the Australian G-NAF lists flats as rows of their own, and the United States National Address Database carries a unit column on a minority of its rows, which is why it never calls a building single. A register that lists no units answers null, never false.

Reference: https://spaw.co/glossary/unit-check