Local numbers
The 020 Number: London's Area Code
020 is the telephone area code for London. It covers the whole of Greater London and is followed by an 8-digit local number — so a London phone number looks like 020 XXXX XXXX. Despite what many people assume, 020 3, 020 7 and 020 8 are not separate area codes; they are all part of the single 020 code.
Want a London number of your own? ONSIM puts an 020 number on your existing mobile from £5/month + VAT — no app, no VoIP, no London office required.
A brief history of the 020 area code
London's phone numbering has changed several times. The city originally used the 01 code, which was split in 1990 into 071 for inner London and 081 for outer London. In 1995 these became 0171 and 0181. Then, in April 2000's "Big Number Change", both codes were merged into a single new code — 020 — with 8-digit local numbers.
Existing numbers kept their identity in the merge: an 0171 number such as 0171 946 0000 became 020 7946 0000, and an 0181 number became 020 8XXX XXXX. That is why so many Londoners still say "0207" and "0208" — but those digits belong to the local number, not the area code.
As demand for London numbers grew, Ofcom opened the 020 3 range in 2005 and the 020 4 range in 2019. Both are allocated across the whole of London.
020 3, 020 4, 020 7, 020 8 — what's the difference?
This is the most common misconception about London numbers. There is only one London area code — 020. The next digit is simply the start of the 8-digit local number:
020 7
Historically central and inner London — these numbers carried over from the old 0171 code. Long associated with established central London addresses.
020 8
Historically outer London — carried over from the old 0181 code. Still widely used across the outer boroughs.
020 3
Introduced in 2005 and allocated London-wide, with no inner/outer distinction. The most common range for newer London numbers.
020 4
The newest range, opened by Ofcom in 2019 as the 020 3 range filled up. Also allocated across the whole of London.
All four ranges are equally valid, equally "London" numbers. Callers pay the same to reach them, and they work identically.
How to dial an 020 number
From anywhere in the UK: dial the full number — 020 followed by the 8-digit local number, e.g. 020 7946 0000.
From a landline within London: you can usually dial just the 8-digit local number, without the 020. From a mobile, always dial the full number.
From abroad: dial +44 20 followed by the 8-digit local number — the leading zero is dropped, e.g. +44 20 7946 0000.
Why businesses want an 020 number
A 020 number is one of the most recognised business numbers in the world. For consultants, startups, agencies and service businesses, a London phone number signals scale and credibility — even if the business operates fully remotely or is based outside the capital.
London-based sole traders and freelancers also use an 020 virtual landline to keep a professional number that rings on their mobile, rather than giving a personal mobile number to clients.
How ONSIM puts an 020 number on your mobile
ONSIM routes incoming 020 calls to your mobile at network level — not through a softphone app that depends on Wi-Fi or data. That gives you reliable call quality wherever you are.
Start with Virtual Landline for inbound calls from £5/mo, then upgrade to Landline SIM from £10/user/mo when you want outbound calls to display your London number too.
Who uses a London 020 number?
An 020 number is useful for a wide range of businesses and individuals, not just those physically based in London.
Remote consultants & freelancers
Professionals who serve London clients but work flexibly use an 020 number to present a consistent London presence without paying for office space or a traditional landline.
National businesses targeting London
Companies based elsewhere in the UK use a London number to signal that they actively serve the capital's market — a particularly common approach for professional services and tech businesses.
Startups & early-stage businesses
London startups that are not yet ready to commit to a permanent office use a virtual landline to maintain a professional phone presence while the team works from wherever they are.
New number or port your existing one
Need a fresh London number? ONSIM can get you started in minutes. Already have a 020 landline? Number porting may be possible — contact us to check eligibility before switching.
Keeping your existing number means no disruption to stationery, your website or customer recognition.
Virtual Landline vs Landline SIM
Virtual Landline (from £5/mo): inbound calls only, rings your current mobile, simplest setup, no hardware.
Landline SIM (from £10/user/mo): inbound and outbound with your 020 number displayed, native mobile experience on a supported device.
We cover more than London
ONSIM supplies local business numbers across 650+ UK area codes. If you need a presence in multiple cities, or want to compare options nationally, we can help.