| Northwood Car Valeting Ltd | Administrative & support | 2024 |
| Northwood Clinic Ltd | Wholesale & retail | 2026 |
| Northwood Dental Practice Ltd | Health & social care | 2020 |
| Northwood Essentials Ltd | Wholesale & retail | 2021 |
| Northwood Laundry and Drycleaners Ltd | Other services | 2024 |
| Northwood Local Ltd | Wholesale & retail | 2024 |
| Northwood Nutrition & Wellness Limited | Administrative & support | 2025 |
| Northwood Pro Shop Limited | Arts & recreation | 2016 |
| Norton Professional Solutions Limited | Professional & scientific | 2026 |
| Nothing Without Labour Limited | Wholesale & retail | 2016 |
| Nourish & Desire Group Ltd | Wholesale & retail | 2026 |
| Nourish Prep Limited | Hospitality | 2023 |
| Novacene Investments LLP | | 2021 |
| Noviogroup AG | Extraterritorial | 2019 |
| NR Lighting Ltd | Professional & scientific | 2025 |
| NSA Executive Services Limited | Professional & scientific | 2018 |
| NSA Management Services Limited | Administrative & support | 2018 |
| NSK Infinity Limited | Real estate | 2017 |
| Nsrs Properties Ltd | Real estate | 2024 |
| NTD National Tracked Dumper Hire Limited | Construction | 2014 |
| NUF Consultancy Limited | Professional & scientific | 1996 |
| Nurmahal Property Investments Ltd | Real estate | 2024 |
| Nursery Road Residents Association Limited | Real estate | 1984 |
| Nutri Vibe Coaching Limited | Health & social care | 2025 |
| Nuvante Technologies Ltd | Financial services | 2025 |
| Nuwave Building and Maintenance Ltd | Construction | 2016 |
| Nuyu London Ltd | Other services | 2011 |
| NWH Supermarket Limited | Wholesale & retail | 2024 |
| NWO Solutions Ltd | Information & communication | 2009 |
| NXT International Ltd | Professional & scientific | 2023 |
| Nyajon Company Limited | Health & social care | 2014 |
| NYT Associates Limited | Administrative & support | 2016 |
| O H Khan Associates Limited | Professional & scientific | 2010 |
| O Mineiro Butcher Ltd | Wholesale & retail | 2021 |
| O'Ezzie Limited | Information & communication | 2018 |
| O'Neill Design Limited | Professional & scientific | 2018 |
| O'Neill Filming Limited | Administrative & support | 2024 |
| OA Estates Limited | Real estate | 2023 |
| Oak & Stone Consultancy Ltd | Professional & scientific | 2023 |
| Oakmain Property Ltd | Real estate | 2002 |
| Oakswood Investments Ltd | Real estate | 2018 |
| Oakwest Birmingham Limited | Real estate | 2004 |
| Oakwood Investment Properties Ltd | Real estate | 2022 |
| OAM Soft Limited | Information & communication | 2016 |
| Obhrai Property Partnership LLP | | 2024 |
| Occom Limited | Real estate | 2006 |
| Ocean Bay Treasures Limited | Wholesale & retail | 2020 |
| Oceansky Logistics Limited | Transport & logistics | 2025 |
| Octrans Ltd | Transport & logistics | 2016 |
| Oculum Films Ltd | Information & communication | 2013 |
| Odessa Trading Ltd | Wholesale & retail | 2021 |
| Odin Advisory Limited | Financial services | 2012 |
| OFA Medical Limited | Health & social care | 2025 |
| Offpeak Activities Ltd | Information & communication | 2026 |
| Offshore Flight Support Ltd | Transport & logistics | 2016 |
| OHG Limited | Real estate | 2018 |
| Okinawa Zest Limited | Information & communication | 2014 |
| Olde Court (Freehold) Limited | Households | 2019 |
| Olde Court Residents Association Limited | Households | 1988 |
| Oleaft Products Limited | Extraterritorial | 2012 |
| Olewatt Limited | Administrative & support | 1993 |
| Oliver James Landscapes Limited | Administrative & support | 2021 |
| OM High School Ltd | Education | 2025 |
| OM Property Investments Limited | Real estate | 2015 |
| OMB Associates Limited | Real estate | 2025 |
| Omega Provisions Limited | Hospitality | 2017 |
| Omelia Corp. Ltd | Financial services | 2025 |
| Omnia Care Ltd | Health & social care | 2021 |
| Omnia Commodities Limited | Extraterritorial | 2018 |
| Omnia Finance Ltd | Financial services | 2025 |
| Omnia Holdings Group Limited | Extraterritorial | 2017 |
| Omnia Holdings Limited | Real estate | 2017 |
| Omnia Management Limited | Real estate | 2022 |
| ON Demand Solutions Limited | Information & communication | 2010 |
| Oncodia Limited | Health & social care | 2006 |
| One Elevated Wellness Limited | Other services | 2025 |
| One Skin UK Ltd | Health & social care | 2022 |
| Onebase Systems Limited | Real estate | 2017 |
| Onit Building Services Ltd | Construction | 2016 |
| Online Airport Cars Ltd | Transport & logistics | 2006 |
| Onlybrush Limited | Wholesale & retail | 2023 |
| Onpoint Deliveries Limited | Transport & logistics | 2025 |
| Onshore Pipeline Engineering Ltd | Real estate | 2014 |
| Onze Limited | Professional & scientific | 2018 |
| Open Science Consulting Limited | Professional & scientific | 2025 |
| Opencapital Ltd | Real estate | 2020 |
| Operator Skills Hub CIC | Administrative & support | 2021 |
| OPT a Therapy Limited | Wholesale & retail | 2023 |
| Optimum Buying Limited | Wholesale & retail | 1996 |
| Optimum Fibre Limited | Other services | 2021 |
| Optimus Consulting & Solutions Ltd | Information & communication | 2026 |
| Optimus Recruits Ltd | Administrative & support | 2020 |
| Opulens Management Company Limited | Households | 2006 |
| Orange and Red Lions Limited | Information & communication | 2017 |
| Orbitgold Limited | Real estate | 1994 |
| Orchid Nails by Bellavesto Ltd | Other services | 2026 |
| Orford Court Freehold Ltd | Real estate | 1996 |
| Orford Court Management Company Limited | Real estate | 2010 |
| Oriannedigital Ltd | Information & communication | 2024 |
| Origin Eight Finance Ltd | Financial services | 2026 |