| Nutribi Limited | Wholesale & retail | 2022 |
| Nutrichem Ltd | Wholesale & retail | 2011 |
| Nutrilife Ltd | Wholesale & retail | 2016 |
| Nutrition Brands Limited | Hospitality | 2015 |
| Nutrition Elegance Ltd | Wholesale & retail | 2026 |
| Nutritioned CIC | Education | 2024 |
| Nutritioneduk Limited | Education | 2021 |
| Nuvaverse Limited | Wholesale & retail | 2025 |
| Nuxi Ltd | Professional & scientific | 2021 |
| Nuxley Ltd | Professional & scientific | 2016 |
| NV Analytical Ltd | Information & communication | 2018 |
| NV Quality Construction Ltd | Construction | 2018 |
| NV Restoration Limited | Other services | 2016 |
| Nvkg Investments Limited | Real estate | 2022 |
| NVP Property Limited | Real estate | 2020 |
| Nvsm Holdings Ltd | Real estate | 2026 |
| Nvsm Limited | Real estate | 2001 |
| NW London Accounting Ltd | Professional & scientific | 2023 |
| NW Prospects Limited | Professional & scientific | 2014 |
| NW10 Enterprise Ltd | Administrative & support | 2017 |
| NW3 Builders Limited | Construction | 2012 |
| Nwandei Enterprise Limited | Transport & logistics | 2009 |
| NWG Limited | Real estate | 1999 |
| Nwjk Shuttle CIC | Transport & logistics | 2025 |
| NWL Building Solutions Ltd | Construction | 2022 |
| NWL Coach Limited | Transport & logistics | 2021 |
| NWL Courses Ltd | Education | 2021 |
| Nxtlvl Limited | Professional & scientific | 2025 |
| NY Cloud Solutions Ltd | Information & communication | 2015 |
| NY Welding Ltd | Construction | 2014 |
| Nyalkaran Auto Limited | Wholesale & retail | 2022 |
| Nyalkaran Limited | Wholesale & retail | 2011 |
| NYK Plastering Ltd | Construction | 2022 |
| Nymble Ltd | Information & communication | 2019 |
| Nymbus Ltd | Information & communication | 2024 |
| Nyrolf Groundworker Ltd | Construction | 2021 |
| NYS Pleroma Ltd | Wholesale & retail | 2024 |
| Nysa Creations Limited | Wholesale & retail | 2012 |
| Nysa Developers Ltd | Real estate | 2023 |
| NYX Medical Limited | Health & social care | 2020 |
| NYX Realty Ltd | Real estate | 2025 |
| NZ Cars Ltd | Wholesale & retail | 2020 |
| O & M Carpets Limited | Administrative & support | 2016 |
| O a F Digital Units Limited | Professional & scientific | 2026 |
| O B B Developments Ltd | Construction | 2020 |
| O Clarks Contractors Ltd | Construction | 2021 |
| O Clarks Ltd | Construction | 2014 |
| O&D Consultants Limited | Information & communication | 2014 |
| O'C Creative Limited | Arts & recreation | 2024 |
| O'Malley Halpin Limited | Real estate | 2015 |
| O'Meara Property Limited | Real estate | 2022 |
| O'Neills Building Company Limited | Construction | 2009 |
| O'Neills Investments Limited | Real estate | 2012 |
| O'Niadh Limited | Hospitality | 2017 |
| O'Reilly Medical Ltd | Education | 2021 |
| O'Rourke IT Ltd | Information & communication | 2019 |
| O. P. L. Limited | Wholesale & retail | 1980 |
| O.A Contracts Ltd | Construction | 2024 |
| O.C.B. (Electrical) Limited | Construction | 1985 |
| O.G Invest Properties Ltd | Real estate | 2025 |
| Oak Grove Ruislip Management Limited | Households | 1986 |
| Oak Lane (Blocks a & B) Flat Management Company Limited | Administrative & support | 1995 |
| Oak LEE Montessori School Limited | Education | 2013 |
| Oak Lodge Management Company Limited | Households | 1988 |
| Oak Operations Ltd | Health & social care | 2023 |
| Oak Wills Limited | Other services | 2024 |
| Oakbey Consultancy Limited | Professional & scientific | 2025 |
| Oakcroft Associates Limited | Professional & scientific | 2017 |
| Oakedge Limited | Construction | 2021 |
| Oaklands Grove Limited | Real estate | 2017 |
| Oakridge Properties 1 Limited | Real estate | 2018 |
| Oakside Court Management Company Limited | Real estate | 2018 |
| Oakstart Limited | Construction | 2024 |
| Oakstone Residential Ltd | Real estate | 2025 |
| Oakvale Property Investments Limited | Real estate | 2026 |
| Oakvera Limited | Financial services | 2025 |
| Oakville 32 Ltd | Real estate | 2020 |
| Oakwood Contracting Ltd | Professional & scientific | 2018 |
| Oakwood Investments U.K. Limited | Real estate | 2023 |
| Oakwood Land Developments Ltd | Real estate | 2026 |
| Oanta Ltd | Administrative & support | 2025 |
| Oascom Ltd | Construction | 2018 |
| Oasis Clinic Limited | Administrative & support | 2003 |
| Oasis Health & Wellbeing Ltd | Health & social care | 2020 |
| Oasis Wholefoods Limited | Wholesale & retail | 1997 |
| OAT Estates Ltd | Real estate | 2020 |
| Oatlands Dental Lounge Limited | Extraterritorial | 2015 |
| OBE Maintenance Ltd | Real estate | 2025 |
| Obelius Limited | Real estate | 2018 |
| Obhrais Limited | Wholesale & retail | 2005 |
| OBI Prestige Garage Limited | Wholesale & retail | 2025 |
| OBI Web Designs Limited | Information & communication | 2025 |
| Object of Desire Ltd | Administrative & support | 2007 |
| Obsideri Capital Assets Management Ltd | Professional & scientific | 2025 |
| Obsidian Pictures Limited | Information & communication | 2017 |
| OC HA1 Ltd | Administrative & support | 2024 |
| Ocasa (UK) Limited | Transport & logistics | 2007 |
| Occasions by Manali Limited | Wholesale & retail | 2023 |
| Occupieriq Ltd | Information & communication | 2026 |
| OCD Consultancy Ltd | Professional & scientific | 2023 |