| NUT London Limited | Wholesale & retail | 2025 |
| Nutch Ltd | Hospitality | 2019 |
| Nuttall Automotive Ltd | Wholesale & retail | 2020 |
| Nutu's Flooring Ltd | Construction | 2022 |
| Nuugold Limited | Other services | 2014 |
| NVC Construct Ltd | Construction | 2025 |
| NVK Accounting Services Limited | Professional & scientific | 2023 |
| NVK Group Limited | Financial services | 2025 |
| NVK Properties Limited | Real estate | 2023 |
| NVT Investments Ltd | Real estate | 2023 |
| NVT Property Ltd | Real estate | 2025 |
| NW3 Capital Ltd | Financial services | 2012 |
| NWA Alayi Holding Ltd | Construction | 2024 |
| Nwabunwanne Limited | Health & social care | 2019 |
| Nwankwo Ltd | Health & social care | 2020 |
| NWW Consulting Limited | Professional & scientific | 2012 |
| NXT Generation Boxing League Limited | Arts & recreation | 2022 |
| NYC Uniforms & DRY Cleaners Ltd | Manufacturing | 2019 |
| Nyklion Services Limited | Construction | 2016 |
| Nyla Housing CIC | Real estate | 2026 |
| Nyrcs Ltd | Wholesale & retail | 2025 |
| NZ Construction Solutions Ltd | Construction | 2018 |
| NZ Partners Ltd | Information & communication | 2023 |
| O & E Property Services Ltd | Real estate | 2025 |
| O L J Property Empire Ltd | Real estate | 2025 |
| O&I Drylining Ltd | Construction | 2022 |
| O' SIX Cuisines Ltd | Hospitality | 2024 |
| O'Brien & Cove Decorating Ltd | Construction | 2022 |
| O'Brien & Sons Limited | Construction | 2020 |
| O'Luli Systems Ltd | Health & social care | 2006 |
| O'Meally Estates Ltd | Real estate | 2021 |
| O'Sullivan Builders Ltd | Construction | 2016 |
| O'Zaika Kitchen's Limited | Hospitality | 2020 |
| O.G PMU Limited | Other services | 2024 |
| O.Imarhiagbe Limited | Health & social care | 2023 |
| O.R. Butterfly Events Limited | Administrative & support | 2018 |
| O2 Mersini Ltd | Construction | 2025 |
| Oak Brokers Limited | Financial services | 2021 |
| Oak Consulting Solutions Limited | Professional & scientific | 2018 |
| Oakburn European Properties Limited | Construction | 1998 |
| Oakburn Investment Holdings Limited | Financial services | 1986 |
| Oakburn Properties Limited | Real estate | 1959 |
| Oakdene Design and Build Ltd | Construction | 2014 |
| Oakes Surveying Ltd | Professional & scientific | 2024 |
| Oakfeild Kennels Limited | Agriculture & fishing | 2019 |
| Oakland Media Ltd | Information & communication | 2014 |
| Oakland Support Services Limited | Health & social care | 2022 |
| Oaklands Decorating Services Limited | Construction | 2010 |
| Oaklands Interiors Limited | Construction | 2026 |
| Oaklands Projects Limited | Construction | 1988 |
| Oakleafe (Dubai) Ltd | Financial services | 2025 |
| Oakleafe Claims (UK) Ltd | Financial services | 2023 |
| Oakleafe Ltd | Professional & scientific | 2023 |
| Oakley Carehomes Limited | Health & social care | 2015 |
| Oakline Properties Midland Limited | Real estate | 2026 |
| Oaks Avenue Limited | Real estate | 2022 |
| Oakshore Limited | Wholesale & retail | 2018 |
| Oakton Support Limited | Health & social care | 2020 |
| Oakway Holdings Limited | Financial services | 2016 |
| Oakwood Mews Limited | Construction | 2021 |
| Oakwood Modern Homes Limited | Real estate | 2024 |
| Oakworth Services Limited | Professional & scientific | 2017 |
| OAM Homecare Ltd | Health & social care | 2026 |
| Oasis Emporium Ltd | Wholesale & retail | 2024 |
| Oasis Mediation Limited | Professional & scientific | 2024 |
| Oasiswell Ltd | Wholesale & retail | 2025 |
| OB Structures Limited | Administrative & support | 2022 |
| Obaid Transport Ltd | Transport & logistics | 2024 |
| Obango Limited | Transport & logistics | 2020 |
| Obango Matrix Logistics Limited | Transport & logistics | 2022 |
| Obango XIX Limited | Real estate | 2021 |
| Obas Properties and Investments Limited | Real estate | 2020 |
| Obdb Data Ltd | Information & communication | 2015 |
| OBI Assets Ltd | Real estate | 2025 |
| Obipelle Limited | Wholesale & retail | 2020 |
| Obsyrn Limited | Wholesale & retail | 2025 |
| Ocean Corporate Hygiene Limited | Wholesale & retail | 2008 |
| Ocean Flights Limited | Administrative & support | 2016 |
| Ocean Holidays Limited | Administrative & support | 2013 |
| Ocean's Renovations Ltd | Construction | 2025 |
| Oceanic Import Ltd | Administrative & support | 2020 |
| Oceanic Supermarket Ltd | Wholesale & retail | 2021 |
| Oceans and Bridges Limited | Information & communication | 2014 |
| Oceans Finance Limited | Professional & scientific | 2016 |
| Oceans Tiles and Flooring Limited | Wholesale & retail | 2025 |
| Octanise Limited | Information & communication | 2017 |
| Octopus Yachts Limited | Wholesale & retail | 2020 |
| Octothorpe Solutions Limited | Extraterritorial | 2015 |
| Oculus Security Management Ltd | Administrative & support | 2019 |
| Odel Security Group Ltd | Administrative & support | 2025 |
| Odey Productions Limited | Information & communication | 2006 |
| Odin Cities Ltd | Administrative & support | 2018 |
| Odintsov Ltd | Administrative & support | 2013 |
| Odysseybjj Limited | Education | 2018 |
| OEG Construction Limited | Construction | 2016 |
| OEG Design & Build Ltd | Construction | 2024 |
| Oeli Ltd | Construction | 2014 |
| Oene Therapy Ltd. | Health & social care | 2022 |
| OEV Cars Limited | Transport & logistics | 2022 |
| OF Enterprises Ltd | Hospitality | 2022 |