| Nwtn Technologies Ltd | Manufacturing | 2018 |
| NWX Capital Limited | Real estate | 2016 |
| NXN Management Limited | Construction | 2023 |
| NXT GEN Mentoring Ltd | Education | 2025 |
| NY Borjan Limited | Professional & scientific | 2018 |
| Nyami Nyami Limited | Administrative & support | 2015 |
| Nyangbalo Ltd | Administrative & support | 2018 |
| Nyansapa Ltd | Information & communication | 2026 |
| Nyanzi and Company Ltd | Transport & logistics | 2017 |
| Nyata Ltd | Information & communication | 2025 |
| Nyati Enterprises Ltd | Administrative & support | 2013 |
| Nybor Properties Limited | Financial services | 2024 |
| Nylah Transport Limited | Transport & logistics | 2026 |
| Nyncom Company Ltd | Wholesale & retail | 2020 |
| NYX Analytics Ltd | Information & communication | 2017 |
| NYX Consultants Limited | Professional & scientific | 2011 |
| NZA Consultancy Ltd | Professional & scientific | 2022 |
| NZP UK Limited | Manufacturing | 1989 |
| Nzwicl Ltd | Public administration | 2023 |
| NØR Wellness Limited | Other services | 2026 |
| NÜD Group Limited | Wholesale & retail | 2026 |
| O & a Security Services Ltd | Administrative & support | 2025 |
| O & H Enterprises Ltd | Other services | 2017 |
| O & W Mortgages Limited | Financial services | 2025 |
| O Aleem Group Ltd | Wholesale & retail | 2024 |
| O Ansah Ltd | Health & social care | 2023 |
| O Brown's Restaurant Ltd | Hospitality | 2018 |
| O C Hamilton Engineering Services Ltd | Professional & scientific | 2016 |
| O Captain Limited | Financial services | 2022 |
| O Imaging Corporation Limited | Information & communication | 1993 |
| O Popoola Dent Ltd | Health & social care | 2025 |
| O Smith Trading Limited | Transport & logistics | 2025 |
| O&K Trading Ltd | Wholesale & retail | 2025 |
| O&L Cleaning Service Ltd | Administrative & support | 2022 |
| O&LCONSTRUCTION1993 Ltd | Construction | 2025 |
| O&M Equestrian Ltd | Agriculture & fishing | 2024 |
| O'Brienlegal Ltd | Professional & scientific | 2025 |
| O'Connell Property Limited | Construction | 2022 |
| O'Connor Construction (Bristol) Limited | Construction | 2007 |
| O'Connor Design Limited | Construction | 2012 |
| O'Connor Invest Ltd | Real estate | 2025 |
| O'Connor Surveying Limited | Professional & scientific | 2018 |
| O'Donnell Konsult Ltd | Health & social care | 2023 |
| O'Keeffe Property Management Ltd | Real estate | 2020 |
| O'Keeffe Transport Ltd | Transport & logistics | 2021 |
| O'Neal UK Limited | Extraterritorial | 2020 |
| O'Neill Creative Limited | Professional & scientific | 2023 |
| O'Neill Publicans Limited | Hospitality | 2025 |
| O'Niversal Ltd | Administrative & support | 2025 |
| O'Sullivan Hughes Audit Limited | Professional & scientific | 2025 |
| O'Sullivan Hughes Limited | Professional & scientific | 2025 |
| O-Generation Ltd | Wholesale & retail | 2026 |
| O-Line Limited | Information & communication | 1990 |
| O.C(Clifton College)Nominees Limited | Education | 1941 |
| O.K. Mortgages Limited | Construction | 2002 |
| O.N.Orbit Strategy Ltd | Professional & scientific | 2025 |
| O.N.S.N Ventures Limited | Hospitality | 2024 |
| O.R Painting and Decorating Ltd | Construction | 2022 |
| O2 Environmental Ltd | Professional & scientific | 2002 |
| O2 Investments Bmw's Ltd | Real estate | 2021 |
| O3ARCH Ltd | Professional & scientific | 2022 |
| O3D Limited | Information & communication | 2013 |
| Oac-Tech Limited | Administrative & support | 2009 |
| Oak & Amber Interiors Ltd | Professional & scientific | 2021 |
| Oak & Barrel Ltd | Hospitality | 2025 |
| Oak & Stone Property Maintenance Ltd | Construction | 2025 |
| Oak and Sage Holdings Limited | Financial services | 2025 |
| Oak and Thyme Trading Limited | Financial services | 2025 |
| Oak Flooring Design Ltd | Wholesale & retail | 2023 |
| Oak Flooring Direct Limited | Wholesale & retail | 2011 |
| Oak Flooring Supplies Limited | Wholesale & retail | 2015 |
| Oak Hair Limited | Other services | 2023 |
| Oak International Forwarding Ltd | Professional & scientific | 2006 |
| Oak Leaf Nurseries 2001 Limited | Wholesale & retail | 2026 |
| Oak Legacy South West Limited | Professional & scientific | 2023 |
| Oak Moors Ltd | Health & social care | 2023 |
| Oak Packing Ltd | Professional & scientific | 2006 |
| Oak Tree Business Park Management Limited | Households | 2020 |
| Oak Tree Hub Ltd | Hospitality | 2023 |
| Oak Tree Mobility Limited | Wholesale & retail | 2009 |
| Oak Tree Road Limited | Professional & scientific | 2012 |
| Oaka Vending (Avon) Ltd | Wholesale & retail | 2025 |
| Oakavon Limited | Real estate | 2023 |
| Oakberry Bristol Ltd | Wholesale & retail | 2024 |
| Oakbridge Education Ltd | Education | 2025 |
| Oakdale Gardens Limited | Construction | 2025 |
| Oakden Music Limited | Information & communication | 2009 |
| Oakdene Pumping Station Management Company Limited | Households | 2015 |
| Oakensen (Bristol) Limited | Professional & scientific | 2018 |
| Oakfern Properties Limited | Real estate | 1978 |
| Oakfern Securities Limited | Real estate | 2021 |
| Oakfield Court 1 (Bradley Stoke) Management Company Limited | Households | 2002 |
| Oakfield Pet Health Clinics Limited | Extraterritorial | 2001 |
| Oakfield Road Management (NO. 4) Limited | Households | 1995 |
| Oakfield Road Offices Ltd | Real estate | 2023 |
| Oakfield Road Properties Ltd | Real estate | 2020 |
| Oakfield Technology Associates Ltd | Professional & scientific | 2018 |
| Oakfield Trustees Limited | Extraterritorial | 1993 |
| Oakgood Property Management Limited | Households | 1981 |
| Oakhaven Group Limited | Wholesale & retail | 2023 |