| New Nova Styles Ltd | Wholesale & retail | 2025 |
| Nextgen Cabling Ltd | Information & communication | 2024 |
| Nexus FB Ltd | Other services | 2017 |
| Nexus Jobs Limited | Administrative & support | 2006 |
| Nfdp Ltd | Other services | 2011 |
| Ngala Properties Limited | Real estate | 2024 |
| Nibodsim Services Limited | Health & social care | 2018 |
| Nifbuk Limited | Health & social care | 2018 |
| Nightingale Way Management Company Limited | Households | 2022 |
| NIK-92 Builders Limited | Construction | 2006 |
| Ninkyo Dantai Ltd | Information & communication | 2025 |
| Nipt Ltd | Information & communication | 2023 |
| Nishan UK Limited | Professional & scientific | 2003 |
| NJ First Builders Limited | Construction | 2021 |
| NMG International Holdings Ltd | Financial services | 2025 |
| Noak Developments Ltd | Real estate | 2025 |
| Noble DBR Ltd | Construction | 2021 |
| Noor Brothers International Ltd | Real estate | 2017 |
| Nootrodoc Health Ltd | Manufacturing | 2025 |
| Noro Ltd | Manufacturing | 2019 |
| North Pole Air Conditioning Ltd | Construction | 2023 |
| North Star Builders Ltd | Construction | 2024 |
| Nova Designs London Ltd | Professional & scientific | 2018 |
| Nova Zest Ltd | Administrative & support | 2024 |
| Novel Dimensions Limited | Education | 2023 |
| Nowiq Ltd | Information & communication | 2025 |
| NRS Investments Limited | Real estate | 2014 |
| NS Healthcare Consultancy Limited | Information & communication | 2026 |
| NSC Trading Limited | Wholesale & retail | 2012 |
| NSM Accounting Ltd | Professional & scientific | 2016 |
| Number Crunchers (London) Limited | Professional & scientific | 2012 |
| Nyutri Ltd | Financial services | 2024 |
| NZN Enterprises Limited | Wholesale & retail | 2025 |
| Oakdale Investments Limited | Real estate | 2007 |
| Oakland Bracknell Ltd | Construction | 2022 |
| Oakland Central Limited | Administrative & support | 2021 |
| Oakland Enfield Limited | Real estate | 2017 |
| Oakland Hildenborough Ltd | Construction | 2018 |
| Oakland Maidstone Care Home Limited | Construction | 2018 |
| Oakland Management & Construction Ltd | Construction | 2025 |
| Oakland Opco B Limited | Financial services | 2021 |
| Oakland Opco Fleet Ltd | Construction | 2025 |
| Oakland Primecare Limited | Professional & scientific | 2016 |
| Oakland Propco 1 Ltd | Construction | 2022 |
| Oakland Propco 3 Ltd | Construction | 2022 |
| Oakland Propco 4 Ltd | Construction | 2022 |
| Oakland Propco a Limited | Financial services | 2021 |
| Oakland Propco B Limited | Financial services | 2021 |
| Oakland Propco C Limited | Financial services | 2024 |
| Oakland Propco C1 Limited | Construction | 2024 |
| Oakland Propco C2 Limited | Construction | 2024 |
| Oakland Propco D Limited | Construction | 2025 |
| Oakland Propco D1 Limited | Construction | 2025 |
| Oakland Propco D2 Limited | Construction | 2025 |
| Oakland Propco H1 Limited | Construction | 2025 |
| Oakland Propco H2 Limited | Construction | 2025 |
| Oakland Propco H3 Limited | Construction | 2025 |
| Oakland Propco H4 Limited | Construction | 2025 |
| Oakland Swanley Care Home Limited | Construction | 2018 |
| Oakland Wantage Care Home Limited | Construction | 2018 |
| Oakoya Ltd | Hospitality | 2022 |
| Oaks Management Company (Woodford Green) Limited(The) | Households | 1982 |
| Oberon Homes Ltd | Real estate | 2024 |
| Oberon Pro Ltd | Construction | 2026 |
| Occupational Therapy Ltd | Health & social care | 2021 |
| OGR Plumbing Ltd | Construction | 2023 |
| Old Loughtonians Hockey Club Limited | Arts & recreation | 2016 |
| Old Loughtonians Services Limited | Arts & recreation | 2020 |
| Oleum Holdings Ltd | Mining & quarrying | 2025 |
| Oliver Logistic London Ltd | Transport & logistics | 2021 |
| OM SAI Global Venture Ltd | Wholesale & retail | 2023 |
| OM Shivshakti Ltd | Construction | 2025 |
| ON Inn Properties Ltd | Real estate | 2019 |
| ON Pointe Marketing Limited | Professional & scientific | 2009 |
| One Compliance Group Limited | Construction | 2025 |
| One Hold Limited | Real estate | 2023 |
| One Stop Gadgets Ltd | Wholesale & retail | 2024 |
| Onel London Ltd | Real estate | 2023 |
| Onespaceclub Ltd | Other services | 2026 |
| Online Buzz Marketing Ltd | Information & communication | 2021 |
| Onsite Ultrasound Limited | Health & social care | 2001 |
| Onyx Risk Consultancy Limited | Professional & scientific | 2025 |
| Opal International LLC Ltd | Wholesale & retail | 2025 |
| Open Plan Invest Ltd | Real estate | 2022 |
| Opengrid Limited | Information & communication | 2026 |
| Openstyx Technologies Ltd. | Information & communication | 2018 |
| Opex Business Solutions Ltd | Information & communication | 2016 |
| Optimal Finishes Ltd | Construction | 2023 |
| ORB Habitat Ltd | Hospitality | 2020 |
| Orbis Health Ltd | Health & social care | 2025 |
| Orchard Tech Supply Ltd | Wholesale & retail | 2026 |
| Orthicventures Ltd | Real estate | 2021 |
| Orysoft Limited | Information & communication | 2016 |
| Oríkì Beads Ltd | Manufacturing | 2024 |
| OS & JS Bhoarla Ltd | Real estate | 2021 |
| OSA Logistics Ltd | Wholesale & retail | 2019 |
| OUR Bubsy & Co Ltd | Wholesale & retail | 2026 |
| Outcome Estates Ltd | Real estate | 2022 |
| Outspan Designs Limited | Professional & scientific | 2018 |
| Outspan Homes Limited | Real estate | 2016 |