| NO1 Sutton Ltd | Other services | 2022 |
| Noah's Heart Limited | Wholesale & retail | 2017 |
| Noahvivek Enterprise Limited | Real estate | 2019 |
| Noble-Son Logistics Ltd | Transport & logistics | 2025 |
| Noctrader Capital Ltd | Other services | 2021 |
| Noisyplanet Ltd | Information & communication | 2023 |
| Nolan Property Management and Services Ltd | Households | 2026 |
| Nomads & Urban Dwellers Ltd | Information & communication | 2021 |
| Nomi Driving School Ltd | Education | 2024 |
| Nomi's Prezzo Ltd | Hospitality | 2020 |
| Nomoreretail Limited | Wholesale & retail | 2010 |
| Nomoros Limited | Information & communication | 2025 |
| Nona UK Limited | Wholesale & retail | 2023 |
| Nonsan Ltd | Other services | 2011 |
| Nonstop Studios Ltd | Information & communication | 2025 |
| Nonsuch Estate Property Limited | Real estate | 2018 |
| Nonsuch Lifts Ltd | Manufacturing | 2023 |
| Nonsuch Medtech Ltd | Manufacturing | 2020 |
| Nonsuch Solutions Ltd. | Information & communication | 2011 |
| Noodle Food Crntre Limited | Hospitality | 2025 |
| Nordic Branding Ltd | Professional & scientific | 2019 |
| Norman Building Services Limited | Construction | 2003 |
| Normanton Consulting Limited | Information & communication | 2007 |
| Norse Consulting Ltd | Construction | 2025 |
| Norstar Technologies Ltd | Professional & scientific | 2020 |
| Northwood (Brighton & Hove) Limited | Real estate | 2025 |
| Northwood (West Sussex) Ltd | Real estate | 2004 |
| Northwood (Worthing) Ltd | Real estate | 2019 |
| Noteology Limited | Information & communication | 2025 |
| Nourish Consulting Limited | Professional & scientific | 2008 |
| Nova Head Spa Limited | Other services | 2025 |
| Novacare Fashion Limited | Wholesale & retail | 2025 |
| Novu Studio UK 2026 Ltd | Wholesale & retail | 2026 |
| Novum Enterprise Ltd | Information & communication | 2026 |
| Novum Health Ltd | Professional & scientific | 2024 |
| NOW Carpets Ltd | Wholesale & retail | 2025 |
| Nplus Limited | Hospitality | 2022 |
| NRC Serv Ltd | Construction | 2026 |
| NRS Construction Ltd | Construction | 2018 |
| NS BJJ Ltd | Wholesale & retail | 2014 |
| NS Decorating Ltd | Construction | 2015 |
| NS Electrical Ltd | Construction | 2025 |
| NS Health Staffing Limited | Administrative & support | 2009 |
| NSB Capital Limited | Financial services | 2024 |
| NSW22 Installations Ltd | Construction | 2022 |
| NSW22 Properties Ltd | Real estate | 2025 |
| NT Concept Limited | Professional & scientific | 2015 |
| NTM Accountants Limited | Professional & scientific | 2023 |
| Nu-Flame Design Limited | Manufacturing | 2023 |
| Nu-Xform Ltd | Information & communication | 2022 |
| NUA Cleaning Ltd | Administrative & support | 2025 |
| NUE Skin Limited | Other services | 2024 |
| Nuespa Limited | Other services | 2025 |
| Nuevo Services Limited | Administrative & support | 2016 |
| Nugents News Ltd | Wholesale & retail | 2019 |
| Number One Thai Restaurant Ltd | Hospitality | 2017 |
| Number Three Limited | Real estate | 1953 |
| Numerix Consultants Limited | Real estate | 2022 |
| Nuparadigm Ltd | Professional & scientific | 2023 |
| Nursery in the Park Day Nursery Ltd | Education | 2024 |
| Nutriish Ltd | Wholesale & retail | 2022 |
| Nuvu Limited | Financial services | 2012 |
| NVC Services Ltd | Other services | 2025 |
| NVR Group Ltd | Transport & logistics | 2015 |
| Nyasa Digital Ltd | Information & communication | 2025 |
| Nylish Ltd | Mining & quarrying | 2022 |
| Nyms Services Ltd | Health & social care | 2018 |
| Nyou Media Limited | Information & communication | 2009 |
| NZ Traders Limited | Other services | 2023 |
| Nzanobi (UK) | Education | 2024 |
| O & T Energy Solutions Ltd | Construction | 2020 |
| O J Solutions Ltd | Construction | 2017 |
| O&3 Limited | Manufacturing | 2017 |
| O'Byrne Investments Limited | Financial services | 2026 |
| O'Law Associate Limited | Professional & scientific | 2022 |
| OAG London Ltd | Professional & scientific | 2023 |
| Oak Lodge Care Home Ltd | Health & social care | 2023 |
| Oak Partnership Limited | Financial services | 2014 |
| Oakandyew Ltd | Agriculture & fishing | 2020 |
| Oakfort Services Limited | Administrative & support | 2026 |
| Oakheath Consultancy Ltd | Information & communication | 2019 |
| Oakland Assets Limited | Real estate | 2002 |
| Oakmont Trading Ltd | Wholesale & retail | 2026 |
| Oakwood Residents Committee Limited | Households | 2003 |
| Oasis Operates Ltd | Wholesale & retail | 2024 |
| OB Construction Ltd | Construction | 2017 |
| Obiri Ltd | Health & social care | 2019 |
| Ocallaghan Cleaners Ltd | Administrative & support | 2025 |
| Oceanguild Limited | Hospitality | 2006 |
| Octopus Audio Limited | Manufacturing | 2019 |
| Ocular Glazing Ltd | Construction | 2018 |
| Oddfit Ltd | Wholesale & retail | 2020 |
| Odoi and Associates Ltd | Manufacturing | 2021 |
| Odun Promotions Limited | Administrative & support | 2003 |
| Odyssey Fitness Limited | Arts & recreation | 2010 |
| OE Esco RH Limited | Energy | 2019 |
| Oerro Energy Limited | Professional & scientific | 2015 |
| Ofegge Ltd | Construction | 2020 |
| Off-Market Dotcom Ltd | Information & communication | 2023 |
| Offer Motorsports Limited | Manufacturing | 2019 |