| Nurse Plus and Carer Plus (UK) Limited | Administrative & support | 2005 |
| Nursery Close Headcorn Management Limited | Households | 2021 |
| Nurturing the Nest Ltd | Administrative & support | 2025 |
| Nusha Developments Ltd | Real estate | 2025 |
| NUT Security Products Ltd | Wholesale & retail | 2015 |
| Nutrilife (Nutriform, Topform) Limited | Professional & scientific | 2000 |
| Nutripolis UK Ltd | Wholesale & retail | 2025 |
| NV Designs Limited | Other services | 2002 |
| NV Scopes Limited | Manufacturing | 2020 |
| Nwoma Ltd | Hospitality | 2024 |
| NXT GNT Barbering Ltd | Other services | 2026 |
| Nygma Limited | Wholesale & retail | 2016 |
| O J Ward Limited | Professional & scientific | 2026 |
| O Malley Aesthetics Ltd | Health & social care | 2025 |
| O S W (Horsmonden) Management Company Limited | Households | 1997 |
| O&M Digital Group Ltd | Information & communication | 2026 |
| O'Brien & Kirk Ltd | Professional & scientific | 2017 |
| O'Donovan Site Services Limited | Construction | 2024 |
| O'Hali Limited | Real estate | 2024 |
| O'Shea Operations Ltd | Real estate | 2020 |
| O2E3 Limited | Real estate | 2025 |
| Oak and Linden Limited | Hospitality | 2023 |
| Oak Develop Ltd | Construction | 2025 |
| Oak Fusion Carpentry & Maintenance Ltd | Construction | 2024 |
| Oak Garden Office Company Limited | Construction | 2015 |
| Oak Therapies CIC | Health & social care | 2020 |
| Oakbest Limited | Professional & scientific | 2003 |
| Oakdene Cottage Ltd | Real estate | 2022 |
| Oakdene House Ltd | Real estate | 2022 |
| Oakflake Limited | Wholesale & retail | 2019 |
| Oakforte Resourcery Ltd | Financial services | 2012 |
| Oaklands Residents Association Limited | Households | 1946 |
| Oakley Home Improvements Ltd | Construction | 2011 |
| Oakmere Opulence Ltd | Construction | 2025 |
| Oakmount Parks Ltd | Hospitality | 2016 |
| Oakover Nurseries Limited | Agriculture & fishing | 1976 |
| Oakray Consultants Limited | Financial services | 2016 |
| Oakshire Rose Ltd | Construction | 2021 |
| Oakside Hire Ltd | Administrative & support | 2020 |
| Oaksreach Limited | Real estate | 2017 |
| Oakwell Design Limited | Professional & scientific | 2015 |
| Oakwood Building Solutions Limited | Construction | 2013 |
| Oakwood Buildings Framing Ltd | Construction | 2022 |
| Oasis Consulting London Limited | Information & communication | 2016 |
| Oasis Consulting Services Ltd | Construction | 2018 |
| Oasis Hair and Cosmetic Centre Ltd | Wholesale & retail | 2024 |
| Oasis-Nels Ltd | Wholesale & retail | 2023 |
| Oast House Marketing Limited | Agriculture & fishing | 2008 |
| Oasthouse Consulting Ltd | Administrative & support | 2013 |
| Oates Property Development Limited | Construction | 2026 |
| Oates Property Group Limited | Real estate | 2026 |
| Oberstein Limited | Households | 2024 |
| OBH Catering Ltd | Hospitality | 2022 |
| OBS Kent Holdings Limited | Financial services | 2026 |
| Obsidia Digital Limited | Information & communication | 2018 |
| Obum Ltd | Health & social care | 2023 |
| OBW Discounts Ltd | Wholesale & retail | 2025 |
| OC1 Ltd | Financial services | 2020 |
| OC1.3 Limited | Financial services | 2023 |
| OC1.4 Ltd | Professional & scientific | 2025 |
| Occupational Health Services (South East) Limited | Health & social care | 2011 |
| Oceanaux Limited | Real estate | 2026 |
| OCL Construction Ltd | Construction | 2025 |
| Octa IT Ltd | Information & communication | 2018 |
| Octadrive Ltd | Wholesale & retail | 2026 |
| Octet Consulting Ltd | Information & communication | 2025 |
| Octet Telecom Limited | Information & communication | 2014 |
| Octobit Ltd | Wholesale & retail | 2019 |
| Odavitt Limited | Wholesale & retail | 2025 |
| Odo's Barn Limited | Hospitality | 2023 |
| ODP Kent Ltd | Professional & scientific | 2005 |
| Odys Building Services Limited | Construction | 2014 |
| Odyssey FX Limited | Financial services | 2021 |
| OFC Distributions Ltd | Wholesale & retail | 2026 |
| OFF Topic Media Limited | Administrative & support | 2024 |
| Offens Agri Ltd | Agriculture & fishing | 2023 |
| OG Exclusives London Limited | Wholesale & retail | 2014 |
| Ogilvie Consultancy Limited | Professional & scientific | 1998 |
| Ogilvie Recruitment Limited | Professional & scientific | 2006 |
| Ogilvie Search Limited | Professional & scientific | 2004 |
| Ogilvie Techncial Limited | Extraterritorial | 2002 |
| Ogplus Ltd | Professional & scientific | 2023 |
| Ogre Services Limited | Construction | 2021 |
| OH Dental Ltd | Health & social care | 2008 |
| Ohali Logistics Ltd | Water & waste | 2026 |
| Ohana Hair Woodham Limited | Other services | 2026 |
| Oikos Place Limited | Real estate | 2023 |
| OIL Heating OIL Cookers Ltd | Construction | 2015 |
| OJP Performance Ltd | Administrative & support | 2019 |
| OJP Property Ltd | Real estate | 2023 |
| OJP Rail Limited | Professional & scientific | 2025 |
| Okanagan Investments Ltd | Real estate | 2020 |
| Okoro Enterprises Limited | Construction | 2013 |
| OLA Visuals Productions Ltd | Information & communication | 2026 |
| Oladimeji Solutions Ltd | Health & social care | 2025 |
| Olan Clinics Limited | Health & social care | 2024 |
| Olan Kent Ltd | Wholesale & retail | 2025 |
| Olcas Holdings Limited | Real estate | 2024 |
| Old Forge Garage Kent Limited | Wholesale & retail | 2014 |
| Old Hall Park Management Limited | Real estate | 2018 |