| NJR Builders Limited | Construction | 2019 |
| NM Finance Limited | Financial services | 2021 |
| NNA Surfleet Limited | Construction | 2022 |
| NNA Surfleet MAN Co Ltd | Households | 2026 |
| NO LAG Limited | Wholesale & retail | 2021 |
| NOJ Coaching Ltd | Other services | 2025 |
| Nolimits Partners Ltd | Information & communication | 2025 |
| Nominal Land Limited | Real estate | 2005 |
| Noord Romjon Financial Services Limited | Financial services | 2016 |
| Norbe Transport Ltd | Transport & logistics | 2026 |
| Nord Transport Ltd | Transport & logistics | 2022 |
| Nordic Asfalt & Anlegg Ltd | Construction | 2024 |
| Nored Transport Limited | Transport & logistics | 2014 |
| Norfolk Landscapes (KL) Ltd | Administrative & support | 2025 |
| Norge Entrepreneur Ltd | Construction | 2025 |
| Normon Grundy & SON Limited | Agriculture & fishing | 1951 |
| North Norfolk Retreats Ltd | Hospitality | 2026 |
| North Steer Limited | Professional & scientific | 2025 |
| Northampton Building Solutions Limited | Construction | 2024 |
| Northlightgreen Ltd | Transport & logistics | 2015 |
| Nottingham and Derby Roofing Ltd | Construction | 2025 |
| Nottingham New Roofs Ltd | Construction | 2023 |
| Nottingham Roofing Solution(Gunthorpe) Ltd | Construction | 2024 |
| Nottingham Roofing Solutions Ltd | Construction | 2023 |
| Nottinghamshire Roofing Ltd | Construction | 2023 |
| Notts Roofing Ltd | Construction | 2021 |
| Nova Property Consultants Limited | Households | 2019 |
| Novastem Limited | Education | 2019 |
| Novem Logistics Ltd | Transport & logistics | 2018 |
| Novo Cosmetics Limited | Other services | 2022 |
| NPO Transport Ltd | Transport & logistics | 2025 |
| Nrfs Holdings Limited | Financial services | 2022 |
| Ns.Storage.Recovery Ltd | Transport & logistics | 2026 |
| Nskt Services Ltd | Construction | 2025 |
| NSX Transport Ltd | Transport & logistics | 2017 |
| NTP Online Learning Limited | Education | 2019 |
| NTW Plumbing & Heating Ltd | Construction | 2021 |
| NU Management Ltd | Professional & scientific | 2024 |
| Numa Property Lettings Ltd | Real estate | 2025 |
| Numentic Ltd | Professional & scientific | 2013 |
| NUT Trans Ltd | Transport & logistics | 2023 |
| Nutri Potential Ltd | Administrative & support | 2025 |
| Nutvigore Ltd | Wholesale & retail | 2025 |
| Nutzu Trans Ltd | Transport & logistics | 2017 |
| Nuweb Solutions Ltd | Information & communication | 2022 |
| NV Lodges Limited | Hospitality | 2026 |
| Nwlewis Properties Limited | Construction | 2026 |
| NWR17 Ltd | Professional & scientific | 2025 |
| O G E Chapman & SON Limited | Extraterritorial | 2008 |
| O&J Services Ltd | Transport & logistics | 2019 |
| O'Connor Cladding & Roofing Ltd | Construction | 2019 |
| O'Connor Landscapes & Driveways Limited | Administrative & support | 2019 |
| O'Connor Landscapes Ltd | Construction | 2018 |
| O'Loughlin Recruitment Ltd | Administrative & support | 2024 |
| O'Neills Property Maintenance Ltd | Construction | 2019 |
| O'Reillys Gutters Ltd | Manufacturing | 2023 |
| O.A. Taylor & Sons Farms Limited | Agriculture & fishing | 2021 |
| Oak and Stone Tree and Landscapes Ltd | Administrative & support | 2026 |
| Oak Bank Solutions Ltd | Water & waste | 2019 |
| Oak Branch Services Ltd | Health & social care | 2025 |
| Oak Wing Limited | Information & communication | 2024 |
| Oakland Construction (Lincs) Limited | Extraterritorial | 2015 |
| Oakland Tree Services Ltd | Administrative & support | 2022 |
| Oakley Group Ltd | Manufacturing | 2024 |
| Oakmont Property Developments Limited | Hospitality | 2016 |
| Oaks Healthcare Ltd | Health & social care | 2022 |
| Oakwood Manor Properties Limited | Administrative & support | 2024 |
| OAT 2012 Limited | Agriculture & fishing | 2012 |
| Ocean&Atria Limited | Health & social care | 2020 |
| Oceanaro Digital Ltd | Professional & scientific | 2021 |
| Oceanbridge Consultants Limited | Transport & logistics | 2023 |
| Octavius Capital Limited | Professional & scientific | 2016 |
| Odagiu Trans Ltd | Transport & logistics | 2016 |
| Odin HR Ltd | Administrative & support | 2020 |
| Odyssey Marine Consultants Limited | Professional & scientific | 2025 |
| OFF the Grid Automotive Ltd | Wholesale & retail | 2026 |
| OFF the Wall Innovations Limited | Hospitality | 2023 |
| OFFICESCAPE360 Limited | Professional & scientific | 2019 |
| Oglesby and Limb Limited | Professional & scientific | 2002 |
| OH My COD (AR) Ltd | Hospitality | 2022 |
| OH My COD Deliveries Ltd | Transport & logistics | 2024 |
| OH My Gosh It's Vegan Ltd | Wholesale & retail | 2020 |
| OKO 3-D Media Ltd | Arts & recreation | 2016 |
| OKO Innovations Limited | Financial services | 2009 |
| OKO Property Limited | Real estate | 2024 |
| OLA Tunmi Ventures Ltd | Administrative & support | 2025 |
| Old B Management Company Ltd | Real estate | 2019 |
| Old Bank Gym Limited | Arts & recreation | 2026 |
| Old Court Builders Limited | Construction | 1981 |
| Old Forge Publishing Limited | Information & communication | 2013 |
| Oldershaws of Moulton Limited | Agriculture & fishing | 1984 |
| Oldfield Lane (Wisbech) Management Company Ltd | Real estate | 2025 |
| Oldwick Installations Limited | Construction | 2014 |
| Olga Haulage Ltd | Transport & logistics | 2017 |
| Olive Tree Spalding Ltd | Hospitality | 2025 |
| Oliver Rose Building Consultancy Ltd | Professional & scientific | 2026 |
| Oliver Rose Developments Ltd | Real estate | 2026 |
| OM Renewables Limited | Professional & scientific | 2024 |
| Omega Automation Ltd | Manufacturing | 2019 |
| Omex Environmental Limited | Manufacturing | 1989 |