| NM Skin Nurse Limited | Other services | 2026 |
| NO Stress Cleaning Ltd | Administrative & support | 2024 |
| North Cornelly Properties Limited | Real estate | 2024 |
| Nosco Management Solutions Ltd | Information & communication | 2012 |
| Nova Tech Distribution Limited | Information & communication | 2024 |
| Novanest Properties Ltd | Real estate | 2024 |
| Novapeak Trading Limited | Wholesale & retail | 2026 |
| Novo Luxe Ltd | Construction | 2023 |
| Novuni Limited | Manufacturing | 2025 |
| NRW Engineering Limited | Wholesale & retail | 2015 |
| NRX Group Ltd | Other services | 2026 |
| NSB Interior Systems Ltd | Construction | 2021 |
| NTA Print Management Ltd | Professional & scientific | 2022 |
| Nucleus Wealth Planning Limited | Financial services | 2018 |
| Numeric Generics Ltd | Information & communication | 2017 |
| Nuocheng Ltd | Wholesale & retail | 2025 |
| Nuskin Medical Aesthetics Ltd | Health & social care | 2022 |
| Nuvolve Limited | Information & communication | 2020 |
| O'Leary Decorators Limited | Construction | 2011 |
| O'Reily Limited | Information & communication | 2022 |
| O2O Leisure Limited | Arts & recreation | 2014 |
| Oak Wood Furniture Manufacturers Limited | Construction | 1994 |
| Oakwell Livery LLP | | 2022 |
| Oasis Traders Ltd | Wholesale & retail | 2026 |
| OBP Abergavenny Limited | Professional & scientific | 2016 |
| OBP Contractors Ltd | Professional & scientific | 2011 |
| Ocean Conveyor Bearing Co., Ltd | Professional & scientific | 2015 |
| Ocupy Group Limited | Financial services | 2022 |
| Ocupy Holdings Ltd | Real estate | 2022 |
| Ocupy Ltd | Real estate | 2018 |
| ODD Clog Designs Ltd | Information & communication | 2013 |
| Offsite Cutting Solutions Limited | Wholesale & retail | 2025 |
| Ohiozoje ONI Limited | Information & communication | 2024 |
| OJ Printing Limited | Wholesale & retail | 2009 |
| Ojagboha & Co Limited | Health & social care | 2019 |
| Old Bridge Pontypridd Ltd | Real estate | 2022 |
| Old Swan Property Support Ltd | Administrative & support | 2017 |
| Old Swan Supplies Ltd | Administrative & support | 2017 |
| Old Swan Tyres Ltd | Administrative & support | 2017 |
| Oliver’S Services Limited | Construction | 2022 |
| Olwen Griffiths Chiropractic Porthcawl Ltd | Health & social care | 2023 |
| OM Hasv Services Limited | Hospitality | 2024 |
| OM Tattoo Studio Limited | Arts & recreation | 2023 |
| OMC Associates Ltd | Information & communication | 2013 |
| Oneland Biotechnology Limited | Wholesale & retail | 2024 |
| Onewomenwalking Ltd | Other services | 2025 |
| Online Decorators (UK) Ltd | Construction | 2016 |
| Online Property Services UK Limited | Construction | 2016 |
| Only SOX Limited | Wholesale & retail | 2025 |
| Onset Accounting Limited | Information & communication | 2019 |
| Oounm Limited | Wholesale & retail | 2026 |
| Opal Avenue Ltd | Other services | 2024 |
| Open-Door-Auto Ltd | Other services | 2011 |
| Optima Heating Limited | Construction | 2003 |
| Optone Consulting Limited | Professional & scientific | 2022 |
| Orange Forestry Limited | Agriculture & fishing | 2002 |
| OS Fire Limited | Public administration | 2026 |
| Osak Security Limited | Administrative & support | 2025 |
| Oseya Holdings Limited | Health & social care | 2025 |
| Oshlowe Properties Limited | Real estate | 2022 |
| Osotto Ltd | Wholesale & retail | 2014 |
| OSR Group Limited | Administrative & support | 2017 |
| Otasi Edu-Consultant and Global Business Services Ltd | Professional & scientific | 2026 |
| Ouest Limited | Hospitality | 2024 |
| Outlook Homes Group Ltd | Real estate | 2022 |
| Outsoled Ltd | Professional & scientific | 2020 |
| Oval E V Technics Limited | Manufacturing | 2022 |
| Oval Publications Limited | Information & communication | 2014 |
| Oval Technics Limited | Information & communication | 2020 |
| Oversail Products Limited | Wholesale & retail | 2024 |
| Owain Evans Heating Limited | Construction | 2015 |
| Owens Wealth Management Ltd | Financial services | 2024 |
| Oyster Accounting Ltd | Professional & scientific | 2022 |
| OZ Vape and Stores Ltd | Wholesale & retail | 2026 |
| P & J Catering Limited | Hospitality | 2002 |
| P & L Spar Limited | Hospitality | 1996 |
| P Allen Builders Limited | Construction | 2016 |
| P and C Balustrading Limited | Construction | 2023 |
| P B Gelatins U.K. Limited | Manufacturing | 1980 |
| P&G Developments Limited | Construction | 2021 |
| P1NK Ltd | Other services | 2018 |
| PA Corp Ltd | Administrative & support | 2017 |
| Pacific Fitness Community Leisure Limited | Arts & recreation | 2014 |
| Paddy O’Bryn’S Limited | Hospitality | 2025 |
| Padel a Paned Holdings Ltd | Arts & recreation | 2026 |
| Padel Cymru Pontypridd Ltd | Arts & recreation | 2026 |
| Padoro Ltd | Wholesale & retail | 2025 |
| Pam's Diner Limited | Hospitality | 2008 |
| Pamc Management Ltd | Professional & scientific | 2017 |
| Panda Global Trading 123 Ltd | Wholesale & retail | 2026 |
| Papa Bravo Ltd | Professional & scientific | 2009 |
| Paratech Maintenance Ltd | Wholesale & retail | 2025 |
| Parc Jiwbili Residential Management Company Limited | Households | 2023 |
| Parfitt Holdings Limited | Financial services | 2023 |
| Parfittness and Wellbeing Ltd | Health & social care | 2026 |
| Park Hall Huyton Ltd | Real estate | 2017 |
| Parker Roofing and Construction Ltd | Construction | 2019 |
| Parlour Limited | Financial services | 2025 |
| PAS & SON Properties Ltd | Real estate | 2025 |
| Pasali Limited | Hospitality | 2009 |