What does a CM99 postcode tell you?

That the address lies in the CM99 district of the CM (Chelmsford) postcode area, and the place OS Open Names most often lists first for its postcodes is Chelmsford. The district alone does not place a street: the inward half of the full postcode narrows the address to one of the district's 75 live postcodes.

CM99 postcode district

CM99, in the CM (Chelmsford) postcode area, has 75 live and 121 terminated postcodes in the ONS Postcode Directory of August 2026, and OS Open Names files no road under it.

postcode area	CM (Chelmsford)
live postcodes	75
terminated postcodes	121
sectors	2
roads listed	0
centroid	51.74250, 0.50063
directory release	2026-08

Postcodes and sectors

75 of the district's 196 postcodes are live in the ONS Postcode Directory of August 2026. A postcode directory says whether a code is in use, never who is there. The live postcodes centre on 51.74250, 0.50063, which locates the district, not a building.

sector	live	terminated
CM99 1	0	33
CM99 2	75	88

Places OS Open Names lists for CM99

Chelmsford
Essex
Eastern

Roads filed under CM99

OS Open Names files no road under CM99, so a street here cannot be confirmed from the register and the lookup answers about the postcode alone.

Check an address in CM99

Common questions about CM99

What does a CM99 postcode tell you?: That the address lies in the CM99 district of the CM (Chelmsford) postcode area, and the place OS Open Names most often lists first for its postcodes is Chelmsford. The district alone does not place a street: the inward half of the full postcode narrows the address to one of the district's 75 live postcodes.

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.
os-open-names · version 2026-11-01 · Contains OS data © Crown copyright and database right 2026, Open Government Licence v3.0.
uk-companies-house · version 2026-10-01 · Companies House free company data product, Open Government Licence v3.0

What each figure means, and what a district page never says, is set out in Reading a British postcode district page; the glossary defines a postcode district, a postcode area, a postcode directory and a street register.

Data synced on 2026-11-01: the newest version among the datasets listed above.

Districts nearest CM99

CM981.6 km
CM22.6 km
CM13.0 km
CM36.2 km
CM410.7 km
CM811.8 km
CM913.6 km
CM1113.8 km
CM1214.0 km
SS1114.1 km
CM7714.2 km
SS1215.3 km
Every district
How a British address is written
Check any address

distance between the districts' centroids

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.

More free tools

All free tools

Need this at scale?

The Spaw API runs the same check with batch and bulk endpoints, monitored address lists, your own suppression list and outcome reporting — 100 free credits a month, no card required.

Get your API key