| Nikka Living Ltd | Real estate | 2024 |
| Nikko Electronics Ltd | Wholesale & retail | 1983 |
| Nikolas Hotels Limited | Hospitality | 2007 |
| Nilec Limited | Professional & scientific | 2002 |
| Nimble Limited | Information & communication | 1996 |
| Nimrod Publications Limited | Information & communication | 1998 |
| Nine 8 Nine Group Ltd | Professional & scientific | 2012 |
| Nine Queen's Park Road (Caterham) Ltd | Households | 2001 |
| Nineteen Avenue South Management Company (1986) Limited | Households | 1986 |
| Nionisle Limited | Administrative & support | 1981 |
| Nippon Kogaku UK Limited | Wholesale & retail | 1979 |
| Nisar & SON Complex Engineering Solutions Ltd | Other services | 2017 |
| Niscot UK Limited | Transport & logistics | 2006 |
| Nisha & S Limited | Information & communication | 2018 |
| Nitram Associates Limited | Real estate | 2002 |
| NJC Services Limited | Professional & scientific | 2002 |
| NJL Plumbing & Heating Limited | Construction | 2019 |
| NMS International Ltd | Hospitality | 2024 |
| NN Homes Ltd | Real estate | 2018 |
| NO Holds Barred Productions Ltd | Information & communication | 2016 |
| NO More IFS OR Buts Ltd | Administrative & support | 2016 |
| NO. 1 Chiltern Road (Sutton, Surrey) Residents Company | Households | 1976 |
| NO. 4 Beauchamp Road (East Molesey) Management Company Limited | Hospitality | 1990 |
| NO. 6 Croft Road Management Company Limited | Households | 1996 |
| NO.3 Developments Ltd | Construction | 2001 |
| NO.9 Boutique & Tanning Ltd | Administrative & support | 2016 |
| NO1PRIVATECONSULTANTS Ltd | Real estate | 2025 |
| Noah B Ltd | Hospitality | 2013 |
| Noah Jacobs & Partners Ltd | Professional & scientific | 2010 |
| Nobbyfilm Limited | Other services | 2004 |
| Noble Premium Finance Limited | Financial services | 2004 |
| Noblebuild Limited | Real estate | 1982 |
| Noisy Chicks Ltd | Professional & scientific | 2015 |
| Nokuhayi Ltd | Health & social care | 2015 |
| Nominees (UK) Limited | Professional & scientific | 2006 |
| Non-Multiplex Cinema Limited | Information & communication | 2007 |
| Norma Limited | Financial services | 2006 |
| Norman Road Haulage (Mitcham) Ltd. | Transport & logistics | 2001 |
| Norman Road Haulage (Wimbledon) Limited | Transport & logistics | 1960 |
| Norman Road Haulage Limited | Transport & logistics | 1980 |
| Norris Raymond Limited | Manufacturing | 2003 |
| Norsette Investment Co. Limited | Real estate | 1964 |
| North and South Labels Limited | Manufacturing | 1999 |
| Northbourne Property Services Ltd. | Households | 2002 |
| Northern Consultants Limited | Professional & scientific | 1989 |
| Northgate UK Trading PVT Ltd | Other services | 2022 |
| Northlands Securities Limited | Financial services | 1967 |
| Northumbria Circuits Limited | Professional & scientific | 1988 |
| Northwest Rental Properties 1 Ltd | Real estate | 2024 |
| Norwood Hill Limited | Real estate | 2017 |
| Norwood Seven Group Limited | Construction | 1967 |
| NOT in My Local Shop Limited | Wholesale & retail | 2002 |
| Novel Business Solutions Limited | Information & communication | 2007 |
| Novus Satus Limited | Health & social care | 2009 |
| NRS Accountancy Services Limited | Professional & scientific | 2005 |
| NRS Residential Properties Ltd | Real estate | 2024 |
| NSR Software Solutions Limited | Information & communication | 2005 |
| Nssr Holdings Ltd | Real estate | 2024 |
| NSW Auto Services Ltd | Wholesale & retail | 2023 |
| NT Training & Consulting Limited | Other services | 2006 |
| NTR Planning Trustees Limited | Professional & scientific | 2024 |
| Nuchemi Ltd | Health & social care | 2011 |
| Nude Consulting Limited | Administrative & support | 2000 |
| Nuffield Health One Limited | Administrative & support | 2018 |
| Nufocus UK Limited | Information & communication | 1998 |
| Number 16 Heathfield Road Management Company Limited | Professional & scientific | 1983 |
| Number 74 Croham Road Management Company Limited | Households | 1984 |
| Number Solutions Limited | Professional & scientific | 2004 |
| Nutfield Nurseries Limited | Real estate | 2017 |
| Nutrisun Limited | Wholesale & retail | 2005 |
| NVP Pharm Ltd | Wholesale & retail | 2026 |
| Nwbsc Limited | Professional & scientific | 2003 |
| Nxtreme Ltd | Information & communication | 2002 |
| O West Consulting Limited | Professional & scientific | 2017 |
| O'Callaghan Recruitment Ltd | Administrative & support | 2023 |
| O'Connor Sokolowski Partnership LLP | | 2001 |
| O.T.M.Servo Mechanism Limited | Manufacturing | 1961 |
| Oak Tree Primary School Ltd | Education | 2023 |
| Oakfield Builders Limited | Construction | 2007 |
| Oakhill Investments Limited | Administrative & support | 1984 |
| Oakland Lodge Ltd | Education | 2011 |
| Oaklands (Shalford) Limited | Real estate | 1956 |
| Oaklawn Trading Estates Limited | | 1980 |
| Oakleaf Enterprise | Health & social care | 1997 |
| Oakley Interiors Limited | Construction | 1997 |
| Oakmaster Systems Limited | Administrative & support | 2002 |
| Oakstave Consulting Ltd | Information & communication | 2003 |
| Oaktree Care Ltd | Health & social care | 2004 |
| Oakverne Limited | Financial services | 2025 |
| Oakwood Bespoke (Camberley) Limited | Wholesale & retail | 2001 |
| Oalrap Contractors Limited | Construction | 2024 |
| OAM Medical Imaging Ltd | Health & social care | 2020 |
| Oasis Water Garden Products (London) Limited | Wholesale & retail | 1981 |
| Obelisk (Caterers) Limited | | 1977 |
| Objects (International) Limited | Information & communication | 1993 |
| OC9 Properties Limited | Real estate | 2019 |
| Ocean Partners Limited | Construction | 2002 |
| Oceanix International Ltd | Manufacturing | 2018 |
| Ocobase Limited | Real estate | 1978 |
| Octogle Technologies Ltd | Information & communication | 2022 |