| North&Safgroup Ltd | Real estate | 2026 |
| Northern Soul Radio Ltd | Information & communication | 2026 |
| Northwest Trader Limited | Construction | 2010 |
| Northwood Freehold Ltd | Construction | 2017 |
| Northwood Wycombe Ltd | Real estate | 2005 |
| Norwaste Limited | Extraterritorial | 1972 |
| Noshahi Food Store Limited | Wholesale & retail | 2020 |
| Noshahi Halal Meat (Birmingham) Limited | Wholesale & retail | 2026 |
| NOT for Corporation Ltd | Wholesale & retail | 2024 |
| NOT FUR Long Ltd | Other services | 2016 |
| NOT Just Mots Ltd | Wholesale & retail | 2021 |
| Noteworthyexperiences Limited | Administrative & support | 2025 |
| Noun Ltd | Professional & scientific | 2017 |
| Nova Executive Cars Ltd | Transport & logistics | 2026 |
| Nova Futures Consultancy Ltd | Health & social care | 2026 |
| Nova LUX Cleans Ltd | Administrative & support | 2025 |
| Nova View Lettings Limited | Real estate | 2026 |
| Novaira Goods Ltd | Wholesale & retail | 2025 |
| Novara Health Collective Ltd | Health & social care | 2026 |
| Novasol Ltd | Professional & scientific | 2025 |
| Novaty Ltd | Health & social care | 2023 |
| NOVE-8 Ltd | Professional & scientific | 2019 |
| Novos Capital Ltd | Real estate | 2019 |
| Novus-Orbis Consulting Ltd. | Professional & scientific | 2024 |
| NPV Ventures Ltd | Hospitality | 2023 |
| NR & SS Limited | Real estate | 2009 |
| NR Auto Centre Ltd | Wholesale & retail | 2026 |
| NRG Carpentry & Joinery Ltd | Construction | 2018 |
| Nrgs PPP Ltd | Wholesale & retail | 2026 |
| NRH Carpentry and Joinery Ltd | Manufacturing | 2026 |
| NRK Holding Ltd | Financial services | 2021 |
| Nrlc Ltd | Mining & quarrying | 2025 |
| NS Building Company Limited | Construction | 2023 |
| NT Collective Limited | Wholesale & retail | 2025 |
| Nubuild Developments Ltd | Real estate | 2026 |
| Nucredo Limited | Professional & scientific | 2008 |
| Nuform Technology Ltd | Information & communication | 2023 |
| Numberexpert Business Services Limited | Professional & scientific | 2016 |
| Numy Limited | Information & communication | 2020 |
| Nurani Digital Limited | Professional & scientific | 2023 |
| Nurs Wellness Clinic Ltd | Other services | 2025 |
| Nursery Lane Builders Limited | Construction | 2021 |
| Nusrat Group Limited | Administrative & support | 2016 |
| Nuthall Ltd | Manufacturing | 2025 |
| Nutrihut Ltd | Wholesale & retail | 2025 |
| Nutrition Dynamics Ltd | Hospitality | 2014 |
| Nutriwise Ltd | Administrative & support | 2014 |
| Nuts About Film and TV Transport Services Ltd | Transport & logistics | 2025 |
| Nuts Kustoms Ltd | Manufacturing | 2025 |
| Nuvotec Ltd | Manufacturing | 2026 |
| Nuvu Life Limited | Manufacturing | 2023 |
| NW London Tilers Ltd | Construction | 2023 |
| NWF Will Services Ltd | Other services | 2025 |
| O & F Electrical Services Ltd | Construction | 2023 |
| O Ahmed Estates Ltd | Real estate | 2026 |
| O Hunt Transport Services Ltd | Transport & logistics | 2023 |
| O Young TM Ltd | Construction | 2025 |
| O&A Property Limited | Real estate | 2024 |
| O'Brien Waste Recycling Solutions Holdings Limited | Financial services | 2015 |
| O'Connor Mechanical Services Ltd | Construction | 2026 |
| O'Hanlon Limited | Professional & scientific | 2025 |
| O'Neill Engineering Consultancy Limited | Professional & scientific | 2016 |
| OAG Limited | Construction | 2007 |
| Oak & Chisel Ltd | Manufacturing | 2023 |
| Oak Lodge Day Centres Ltd | Health & social care | 2025 |
| Oak Lofts & Extensions Ltd | Construction | 2021 |
| Oak Seeds Ltd | Wholesale & retail | 2021 |
| Oakdene Consulting Ltd | Professional & scientific | 2025 |
| Oakengrove Court Freehold Company Ltd | Households | 2023 |
| Oakengrove Court Management Company Limited | Households | 1982 |
| Oakengrove House Limited | Real estate | 2008 |
| Oakfield Electrical Limited | Construction | 2005 |
| Oakfield Housing Limited | Real estate | 2025 |
| Oakleaf Farm Ltd | Administrative & support | 2009 |
| Oakleigh Dental Practice Limited | Health & social care | 2013 |
| Oakleigh House Ltd | Health & social care | 2025 |
| Oakley Wood Pastures Limited | Agriculture & fishing | 2024 |
| Oakvale Joinery Limited | Manufacturing | 1998 |
| Oakwood Events Limited | Administrative & support | 2011 |
| Object Conservation & Mountmaking Ltd | Administrative & support | 2024 |
| Objective Integration Limited | Manufacturing | 2015 |
| OBR Construction Limited | Construction | 2010 |
| OBR Plant UK Limited | Construction | 2014 |
| Obstrepo Limited | Information & communication | 2003 |
| OCB Papers (UK) Limited | Manufacturing | 2011 |
| OCD Clean Ltd | Administrative & support | 2026 |
| OCD Construction Ltd | Construction | 2025 |
| OCD PCB Ltd | Manufacturing | 2025 |
| Ocean Media and Public Relations Ltd | Information & communication | 2004 |
| Ochre Triangle Ltd | Administrative & support | 2020 |
| OCS Heating and GAS Limited | Construction | 2020 |
| Octa Custom Renovations Ltd | Construction | 2018 |
| OCV Property Ltd | Hospitality | 2024 |
| Oddbears Ltd | Professional & scientific | 2025 |
| Odigia Limited | Professional & scientific | 2025 |
| Odin's Hospitality Limited | Hospitality | 2021 |
| Odunade Group Ltd | Wholesale & retail | 2026 |
| Odyssey Event Professionals Ltd | Arts & recreation | 2014 |
| Office Hunters Ltd | Real estate | 2020 |
| Offistock Limited | Wholesale & retail | 2021 |