Do Croydon, Hounslow and Stratford share the same 020 as central London?

Yes. The 020 area covers all 32 London boroughs together with the City, so a business in Croydon, Hounslow, Stratford, Wimbledon, Hammersmith or any other borough receives a full 020 number rather than a separate suburban code. Heathrow Airport and the surrounding commercial estates also fall inside the 020 area, which means airport-adjacent operators carry the same prefix as a head office in the City.

Why doesn't Watford fall under 020 when it sits right on the M25?

Watford has its own 01923 area code because it lies in Hertfordshire, outside the Greater London administrative boundary that Ofcom uses to define the 020 numbering area. The same applies to Dartford (01322), Epsom (01372), St Albans (01727) and Slough (01753), all of which feel like commuter London but sit in neighbouring counties. Businesses registered there should apply for the relevant local code or pair a regional number with a national 0333 line for UK-wide reach.

Are 020 numbers still available or has the prefix filled up?

Stock is healthy. The 020 area runs across four sub-ranges — 020 3, 020 4, 020 7 and 020 8 — and Ofcom released the 020 4 range in 2019 precisely so that the older sub-ranges could keep serving long-standing London subscribers without exhausting the supply. Because London has the highest call density in the UK, memorable digit patterns (consecutive digits, mirror sequences, postcode matches) sell down faster than in any other area, while ordinary 020 numbers activate within one working day.

What if my business is outside London but most of my customers are there?

A 020 number fits that situation well, because it needs no London address. Your London customers call a local number at the normal rate, and the calls ring through to your team wherever it sits. A national 0333 number gives you UK-wide reach at standard geographic call rates. A freephone 0800 line works for sales hotlines and marketing campaigns where the call cost should sit with you rather than the caller. Both can run alongside a 020 number on the same account.

020 Area Code | Which Towns It Covers

Q: Can any UK business apply for a 020 number?

Yes, and so can a business outside the UK. Ofcom’s National Telephone Numbering Plan allows a geographic number to be assigned outside its area when the business has asked for that area code and callers pay the normal rate for it. The number registers on your own business address, which can be anywhere in the UK or abroad, so a company in Manchester, Leeds or Glasgow can publish a 020 number for its London customers without a London office. CallFactory checks your business details before the line goes live.

Area code 020 identifies London, and callers across the capital read a 020 number on a website, an invoice or a Google Business Profile as a London line. You do not need an office in London to use that signal, because Ofcom’s National Telephone Numbering Plan lets a business outside the area take a 020 number as long as it asked for that code and callers pay the normal rate for it. For companies expanding into the capital, restructuring after a merger or moving a head office, it pays to know precisely which towns sit inside the 020 area and which sit just outside.

This article maps the 020 coverage in detail, explains what Ofcom’s numbering plan says about who can hold the prefix, and walks through what you need to order a number. From there, applying for a 020 number for your London business becomes a predictable exercise.

Which towns does the 020 area code cover?

The 020 area covers Greater London — every one of the 32 boroughs together with the City of London — and the surrounding commercial estates that sit inside the M25 ring. The principal centres inside the area:

City of London — the Square Mile; banking, insurance, legal services and the lion’s share of UK financial-services headquarters
Westminster — government, professional services, the West End retail core and the political and media press around Whitehall
Camden, Islington, Hackney and Tower Hamlets — the inner-east tech and creative cluster running from King’s Cross through Shoreditch to Canary Wharf
Southwark, Lambeth and Wandsworth — South Bank, Vauxhall, Battersea and the Nine Elms regeneration corridor, dense with creative agencies and consultancies
Hammersmith & Fulham, Kensington & Chelsea and Brent — west London media, luxury retail, hospitality and the Wembley regeneration zone
Hounslow and Hillingdon — Heathrow Airport, the surrounding cargo and hotel estates, plus Brunel University and the A4 corridor
Croydon, Sutton, Kingston upon Thames, Merton and Richmond — south London’s secondary business districts, with strong professional-services and insurance clusters in Croydon and Wimbledon
Bromley, Bexley, Greenwich and Lewisham — south-east London, the O2 cluster, North Greenwich and the Bexley logistics belt
Newham, Barking & Dagenham, Havering and Redbridge — east London, Stratford and the Olympic Park legacy, the Romford retail core and the A13 logistics corridor
Enfield, Haringey, Waltham Forest, Barnet and Ealing — north and outer-west London, with Wembley-adjacent manufacturing in Brent flowing into Park Royal

Callers across all of these boroughs recognise a 020 number as a London line and pay the normal geographic rate to reach it. Your own office does not have to sit inside Greater London, because the number registers on your business address wherever that is, in the UK or abroad.

Why the geographic rule exists

UK area codes were designed so that the leading digits of a phone number tell the caller, and the caller’s billing system, which part of the country the line sits in. A 020 says: this line belongs to London. A 0161 says: Manchester. A 0117 says: Bristol. The numbering plan does not, however, require the business behind the number to be in London. Clause B3.1.1 of Ofcom’s National Telephone Numbering Plan, headed “Out of Area use of Geographic Numbers”, allows a geographic number to be assigned to a subscriber outside the area, provided the subscriber asked for a number with that area code and calls to it are charged in line with calls to any other number with that code.

In practice a 020 number is open to your business whether your office is in London, in another UK city or outside the UK. You ask for the code by choosing a 020 number, and callers pay the normal rate for a London number, so both conditions are met from the start. The number registers on your own business address wherever that is, and CallFactory checks your business details before the line goes live, in line with Ofcom’s guidance that providers confirm a customer is a genuine business.

That makes the UK more open than many continental European markets, where a local geographic number often requires an address inside the numbering zone. A London firm, a Manchester company that wins customers in the capital and an overseas business entering the British market can all publish a 020 number, and in each case London customers call a local line while the calls ring through to the team wherever it sits.

Boundary cases around London

Greater London ends sharply at the M25 in some places and meanders through the commuter belt in others, so a number of well-known towns that look like they should be on 020 in fact sit on a different code. The principal cases:

Watford — north-west, area code 01923 (Hertfordshire). A short hop from the Northern Line at Stanmore, but Watford lies outside the Greater London boundary
Dartford and Gravesend — east, area code 01322 (Kent). Bexley to the west of the Dartford Crossing keeps 020; everything east of it switches to 01322
Epsom and Leatherhead — south, area code 01372 (Surrey). Inside the M25 in places but in Surrey for postal and telecoms purposes
Reigate and Redhill — south, area code 01737 (Surrey). Often quoted as London commuter towns; legally and for telecoms purposes they belong to Surrey
St Albans and Hemel Hempstead — north-west, area code 01727 and 01442 (Hertfordshire)
Slough and Maidenhead — west, area code 01753 and 01628 (Berkshire). Slough trading estate sits outside Greater London, even though its labour market overlaps heavily with west London
Brentwood and Romford parts — east, area code 01277 (Essex) and 01708 (Romford). Most of the London Borough of Havering uses 020, but the older Romford exchange retains 01708 in places, which trips up newcomers

These boundary cases matter for two reasons. First, callers judge a number by its code rather than by the map, so a business whose customers sit in Watford or Dartford reaches them better with 01923 or 01322 than with 020. Second, they map cleanly onto a multi-site structure: a Watford head office can keep its 01923 line while a Croydon branch carries a separate 020, with both routed through the same CallFactory account so that callers and staff treat them as one phone system.

How the 020 area grew historically

London’s numbering history is denser than that of any other UK area, because the capital was the first part of the country to run out of subscriber capacity. The original London code was 01 until 1990, when Phoneday split the capital into 071 (Inner London) and 081 (Outer London) so that two separate ranges could accommodate the rising fax and second-line traffic of the late 1980s. PhONEday in 1995 added a leading “1” to every UK area code, taking 071 to 0171 and 081 to 0181. Five years later, in April 2000, Ofcom merged 0171 and 0181 into the single 020 area we use today, with the old subscriber numbers prefixed by a leading 7 or 8 — which is why so many long-standing London numbers still start 020 7 or 020 8.

The 020 3 range was opened in 2005 once the older sub-ranges began to fill, and 020 4 followed in 2019 as the capital’s call density continued to climb. All four sub-ranges sit inside the same Greater London numbering area, so the leading digit after 020 carries no geographic meaning whatsoever — a 020 7 line in the City and a 020 4 line in Croydon are equally valid London numbers, and most modern London businesses pick whichever sub-range produces a memorable digit pattern rather than worrying about historic associations. Heathrow’s commercial estates were folded into the same area from the outset, which is why Heathrow-adjacent operators carry 020 alongside the City and Canary Wharf rather than a separate west-London code.

How to apply for a 020 number

Ordering a 020 number takes a few minutes, and none of the steps depends on where your office is:

Choose your number. Pick an ordinary 020 number or a memorable digit pattern. No London office, branch or serviced address is needed for either.
Give your business details. Enter your company name and business address. The number registers on that address, which can be anywhere in the UK or abroad, so a registered office in Manchester, a head office in Glasgow and a company address outside the UK are all accepted.
Submit the application. CallFactory checks your business details at the point of order, holds the number while the verification clears (typically the same morning) and activates the line within one working day.

Edge cases come up frequently. A Manchester company that wins customers in London can publish a 020 number without opening an office there, and keep the same number if it later takes space in Soho. A move from one London borough to another does not require a new number — porting keeps the existing 020 in place. A multi-site business with several London locations can put each branch on its own 020 sub-range and route them all through one CallFactory call flow, which means a single team handles the whole estate without callers noticing.

If your business is outside the 020 area

A business outside the 020 area can still take a 020 number, because it registers on your own business address wherever that is. When your callers are not in London, another number can fit better. The fit depends on whether you want a regional identity, a national presence or a freephone hotline.

A neighbouring local code — 01923 for Watford, 01322 for Dartford, 01372 for Epsom, 01727 for St Albans. Useful for businesses that genuinely belong to the commuter belt and want a recognisable local identity rather than a London claim
A national 0333 number — 0333 number charged at standard geographic call rates regardless of where the caller dials from. Suits operators with a UK-wide remit who want one published line for every region
A freephone 0800 line — 0800 freephone number where the caller pays nothing and the cost sits with the business. The classic fit for sales hotlines, customer-service campaigns and inbound marketing
A national overview — the UK phone-numbers overview lays out every range Ofcom administers, with guidance on which one suits each commercial profile

The right alternative depends on where you want the brand to sit. A regional code reads as authentically local; a 0333 reads as nationally credible; a 0800 prioritises caller convenience over geographic identity. The full feature set, monthly cost and contract terms across all of them are listed on the pricing page.

Get started

If you want a 020 line live this week, apply through the London 020 number page. CallFactory checks your business details, holds the number for you and activates the line within one working day, complete with call forwarding to a mobile or landline, a text-to-speech welcome message in any language and call recording for compliance and training.

The same order works for a London firm, for a company elsewhere in the UK that serves customers in the capital and for a business outside the UK, because the number registers on your own business address wherever it is. If your customers are spread across the whole country, a 0333 national number covers them with one line, and it pairs neatly with a 020 number for the London market.

Which towns does the 020 area code cover and what it means for your business