HA4 postcode district

Postcodes and sectors

1,137 of the district's 1,827 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 51.57029, -0.41067, which locates the district, not a building.

Companies registered in HA4

Companies House lists 11,046 companies with a registered office in HA4; 7,140 of them at addresses shared by 25 or more companies (1 October 2026 snapshot). 25 is the count at which the address lookup reports a company cluster.

Places OS Open Names lists for HA4

• Greater London
• London
• Hillingdon
• Ruislip
• Harrow

Roads filed under HA4

Named roads first, then numbered ones. 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. Great Britain has no open register of buildings, so a listed road never means a building on it exists.

• Abbot Close
• Abercorn Grove
• Acacia Avenue
• Acol Crescent
• Acorn Grove
• Aitken Close
• Aldridge Avenue
• Allonby Drive
• Almond Close
• Angus Drive
• Appledore Avenue
• Aragon Drive
• Ardley Close
• Arla Place
• Arlington Drive
• Ashburton Road
• Barnstaple Road
• Barnwood Close
• Beaufort Road
• Bec Close
• Bedford Road
• Beech Avenue
• Beechwood Avenue
• Bell Close
• Bembridge Gardens
• Bempton Drive
• Berkeley Close
• Bessingby Road
• Beverley Road
• Bideford Road
• Bishop Ramsey Close
• Blagrove Crescent
• Blaydon Close
• Blenheim Crescent
• Boleyn Drive
• Boston Grove
• Bourne Avenue
• Bourne Court
• Brackenbridge Drive
• Bradfield Road
• Braintree Road
• Breakspear Road
• Brickett Close
• Brickwall Lane
• Bridgwater Road
• Brixham Crescent
• Broadhurst Gardens
• Broadwood Avenue
• Bromley Crescent
• Brook Close
• Brook Drive
• Bury Avenue
• Bury Street
• Cambridge Drive
• Campbell Close
• Canfield Drive
• Cardinal Road
• Carmichael Close
• Castleton Road
• Cavendish Avenue

Check an address in HA4

Check an address in HA4

The same road list through the API, from the outward code alone:

curl "https://spaw.co/api/v1/address/streets?country=GB&postal_code=HA4" \
  -H "Authorization: Bearer $SPAW_KEY"

Common questions about HA4

What does an HA4 postcode tell you?

That the address lies in the HA4 district of the HA (Harrow) postcode area, and the place OS Open Names most often lists first for its postcodes is Ruislip. The district alone does not place a street: the inward half of the full postcode narrows the address to one of the district's 1,137 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 HA4

• HA53.2 km
• HA23.4 km
• UB103.7 km
• UB53.8 km
• HA64.7 km
• UB44.9 km
• HA15.1 km
• UB85.9 km
• UB95.9 km
• UB66.0 km
• UB16.6 km
• HA36.7 km
• Every district
• How a British address is written
• Check any address

distance between the districts' centroids