| Novalis Mental Health Ltd | Health & social care | 2025 |
| Novaplex Business Solutions Limited | Information & communication | 2008 |
| Novatiq Limited | Information & communication | 2019 |
| Novatiq Solutions Limited | Information & communication | 2014 |
| Novatiq Technologies Limited | Information & communication | 2014 |
| Novellium Limited | Information & communication | 1999 |
| Novem FM Limited | Construction | 2021 |
| Novexel Limited | Administrative & support | 2025 |
| Novofinity United Kingdom Limited | Professional & scientific | 2024 |
| Novoli Farm Limited | Hospitality | 2021 |
| Novus Crest Ltd | Health & social care | 2026 |
| NOW Hear Ltd | Wholesale & retail | 2021 |
| NOW Plus Limited | Professional & scientific | 2022 |
| NOX Ltd | Other services | 2023 |
| Noyack Limited | Real estate | 2019 |
| NP Globe Medical Ltd | Health & social care | 2021 |
| NPS Builders (Suffolk) Limited | Construction | 2001 |
| Nps-Uk Limited | Real estate | 2016 |
| NR Essex Ltd | Real estate | 2021 |
| NRC Associates Ltd | Real estate | 2019 |
| NRG Contracting Ltd | Construction | 2011 |
| NRJ Ecom Limited | Wholesale & retail | 2020 |
| NRJ Property Management Ltd | Hospitality | 2023 |
| NRP Stores Limited | Wholesale & retail | 2025 |
| NS LAB Limited | Wholesale & retail | 2020 |
| NSM Cleaning Services Ltd | Administrative & support | 2019 |
| Nssp Ltd | Information & communication | 2016 |
| Nssr Estates Ltd | Real estate | 2026 |
| NTC Services Limited | Professional & scientific | 1997 |
| NTP Building Services Limited | Construction | 2015 |
| Nucleus Eastwood Essex Management Limited | Households | 2005 |
| Nucluesq Solutions Limited | Information & communication | 2026 |
| Nudge Creative Labs Limited | Professional & scientific | 2018 |
| Nuform Limited | Administrative & support | 2017 |
| Nuhuco Ltd | Other services | 2011 |
| Nukleuz Limited | Professional & scientific | 2017 |
| Nuland Ltd | Professional & scientific | 2022 |
| Numantia Health Ltd | Information & communication | 2017 |
| Number One Investments Limited | Households | 2016 |
| NUMBER1 Snack Station Ltd | Wholesale & retail | 2025 |
| Numiscan Chelmsford Ltd | Health & social care | 2024 |
| Numiscan Colchester Ltd | Health & social care | 2025 |
| Nunn Syndication Limited | Professional & scientific | 1992 |
| Nuova Corporation Ltd | Financial services | 2019 |
| Nurjahan Limited | Hospitality | 2015 |
| Nurse Elite Ltd | Health & social care | 2026 |
| Nursery Kitchen Limited | Manufacturing | 2015 |
| Nurture Bridge Education Consultancy Ltd | Education | 2026 |
| Nurturewell Care Ltd | Health & social care | 2023 |
| Nutmeg Properties Ltd | Real estate | 2019 |
| Nuton Green Energy Ltd | Energy | 2025 |
| Nutraspose Ltd | Wholesale & retail | 2025 |
| Nuvest Limited | Real estate | 2004 |
| NW Consultants Limited | Professional & scientific | 2003 |
| NWM Limited | Other services | 2019 |
| NWM Projects Limited | Other services | 2019 |
| NWM Properties Limited | Other services | 2018 |
| NWS Consultant Engineering Limited | Professional & scientific | 2020 |
| Nwtf Trading Limited | Construction | 2014 |
| Nxtgen Electrical Services Ltd | Construction | 2022 |
| Nxtphase Property Ltd | Real estate | 2025 |
| Nyfta Digital Limited | Wholesale & retail | 2025 |
| O & C Investments Limited | Real estate | 2022 |
| O & M Collections Ltd | Transport & logistics | 2026 |
| O My Designs Ltd | Professional & scientific | 2020 |
| O'C Construction & Sons Ltd | Construction | 2024 |
| O'Connor & Company Cars Ltd | Wholesale & retail | 2023 |
| O'Connor & Company MEP Ltd | Real estate | 2020 |
| O'Connor & Company Technologies Ltd | Wholesale & retail | 2023 |
| O'Donnell Surf Limited | Information & communication | 2007 |
| O'Kale Services Limited | Real estate | 2022 |
| O'Rich Ltd | Hospitality | 2023 |
| O.J.M Property Management Ltd | Real estate | 2012 |
| O.J.M Solutions Ltd | Professional & scientific | 2005 |
| Oak & Iron Construction Ltd | Construction | 2025 |
| Oak PAY Ltd | Wholesale & retail | 2023 |
| Oak Properties Limited | Real estate | 2015 |
| Oakberry Homes Ltd | Construction | 2022 |
| Oakbrook Moorings Limited | Construction | 2012 |
| Oaklea Construction Group Ltd | Construction | 2023 |
| Oakleigh Solutions Ltd | Real estate | 2014 |
| Oakley Farm Holdings Ltd | Financial services | 2025 |
| Oakridge Company Management Ltd | Financial services | 2025 |
| Oakroom Wealth Management Ltd | Administrative & support | 2015 |
| Oaks Croft Limited | Real estate | 2018 |
| Oaks Online Shopping Company Ltd | Wholesale & retail | 2009 |
| Oaks Place Limited | Health & social care | 2025 |
| Oakspire Estates Ltd | Real estate | 2026 |
| Oakstone Contracting Limited | Construction | 2021 |
| Oaktown Limited | Real estate | 2010 |
| Oakview Construction Ltd | Construction | 2023 |
| OAL Legal Limited | Professional & scientific | 2020 |
| Oasis Care-Uk Limited | Public administration | 2016 |
| Oasis Homes for Children Ltd | Health & social care | 2021 |
| Oasis Services Partnership Ltd | Professional & scientific | 2019 |
| Oats on the Tracks Ltd | Hospitality | 2026 |
| OB Property Ltd | Real estate | 2019 |
| Obelisk Consultancy Limited | Information & communication | 2017 |
| Obeng Splendour Developments Ltd | Real estate | 2024 |
| Obex Recruitment Ltd. | Administrative & support | 2018 |