What does a CM20 postcode tell you?

That the address lies in the CM20 district of the CM (Chelmsford) postcode area, which the directory places around Eastern. The inward half of the full postcode narrows it to a street or a building; the district alone does not, and an address written with a district and no inward half cannot be checked against the register.

Does a street listed here mean an address on it exists?

It means OS Open Names lists a road of that name under the district, which is what the address lookup answers as a street-level match. It says nothing about any building on it: Great Britain publishes no open register of buildings, so the lookup answers exists: null there and confirms the street alone.

Who lives at these postcodes?

Nobody on this page. A postcode directory says whether a code is in use, never who is there, and a streets register lists roads, not occupants. The address lookup carries no field about a person and never will.

CM20 postcode district

What the public directories installed here say about the CM20 postcode district: how many of its postcodes are in use, the places OS Open Names lists for them, the streets it files under the district and the district's centroid. Counted from the national postcode directory and OS Open Names on 2026-09-18, and never about who is at an address.

postcode area	CM (Chelmsford)
live postcodes	629
terminated postcodes	620
streets listed	169
centroid	51.77566, 0.10276
counted on	2026-09-18

Places the directory lists for CM20

OS Open Names places the district's postcodes in these settlements, boroughs, counties and regions, most often first. A town written as any of them matches the directory in an address lookup, and one written as another place in the CM area is reported but not scored.

Eastern
Harlow
Essex
East Hertfordshire
Hertfordshire
Eastwick
Gilston

Postcodes in use

629 postcodes in CM20 were in use on the day of the count. A postcode directory says whether a code is in use, never who is there. 620 of its 1,249 postcodes have been terminated: a real address written with one has moved on, which is not the same thing as a typo, and the address lookup scores it rather than refusing it.

Centroid: 51.77566, 0.10276 — the mean of the live postcodes' centroids, which locates the district, not any building in it.

Streets filed under CM20

OS Open Names files 169 roads under CM20. A road is filed under one district even where it runs through several, so a street missing here may be listed under a neighbouring district — which is why the address lookup never calls a British street absent.

A1019
A1025
Adams House
Altham Grove
Amberry Court
Arbour Mews
Arkwrights
Ash Tree Field
Bishop Close
Blackbush Spring
Blackbush Springs
Bowhill Way
Bowlby Hill
Bracewell Place
Bramble Rise
Broadfield
Broad Walk
Bromley Close
Broomfield
Burnt Mill

the first 20 of 169, alphabetically

Check an address in CM20

The address checker opens on Great Britain with the district in the field: add the street, the number and the full postcode, and it answers the postcode's status, whether the street is filed under the district, and what kind of delivery point the address names.

Check an address in CM20

curl https://spaw.co/api/v1/address \
  -H "Authorization: Bearer sk_live_…" \
  -H "Content-Type: application/json" \
  -d '{"address": "10 Downing Street, London CM20 …", "country": "GB"}'

Common questions about CM20

What does a CM20 postcode tell you?: That the address lies in the CM20 district of the CM (Chelmsford) postcode area, which the directory places around Eastern. The inward half of the full postcode narrows it to a street or a building; the district alone does not, and an address written with a district and no inward half cannot be checked against the register.
Does a street listed here mean an address on it exists?: It means OS Open Names lists a road of that name under the district, which is what the address lookup answers as a street-level match. It says nothing about any building on it: Great Britain publishes no open register of buildings, so the lookup answers exists: null there and confirms the street alone.
Who lives at these postcodes?: Nobody on this page. A postcode directory says whether a code is in use, never who is there, and a streets register lists roads, not occupants. The address lookup carries no field about a person and never will.

Where the counts come from

ons-postcode-directory · version 2026-08 · Contains ONS, OS and Royal Mail data © Crown copyright and database right 2026, Open Government Licence v3.0. Northern Ireland postcodes are excluded: their reuse needs a Land & Property Services licence.

Data synced on 2026-09-18: the newest register or postcode directory copy installed here.

Other districts in CM

Wrong result, or is it about you? If this tool said something you think is wrong, tell us and a person reads it. If Spaw is holding data about you and you never signed up here — a customer may have had your address verified, or reported that a message to it bounced — erase it yourself, confirmed by mail to that address and with no account needed.

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