| Nova Reformer Pilates Limited | Arts & recreation | 2025 |
| Novamat Limited | Public administration | 2016 |
| NR Datasolutions Limited | Information & communication | 2023 |
| NRA Trans Limited | Administrative & support | 2016 |
| NRG (Engineering) Limited | Professional & scientific | 2007 |
| NRG Marketing Ltd | Administrative & support | 1998 |
| NS Tree and Landscaping Contractors Ltd | Administrative & support | 2022 |
| Ns&Grupz Limited | Wholesale & retail | 2025 |
| NU Automation Ltd | Construction | 2025 |
| Nu-Phalt Limited | Construction | 2003 |
| Nudge Forward Ltd | Professional & scientific | 2022 |
| NUK Health & Performance Ltd | Health & social care | 2025 |
| Number 108 Real Estate Ltd | Real estate | 2026 |
| Numflex Limited | Professional & scientific | 2018 |
| Nuneaton Nepalese Football Club Ltd | Arts & recreation | 2025 |
| Nuneaton Regrinds Ltd | Manufacturing | 2019 |
| Nuneaton Transport Ltd | Transport & logistics | 2019 |
| Nuro Enterprise Ltd | Hospitality | 2022 |
| Nursery Elite Ltd | Financial services | 2020 |
| Nurtured Minds Ltd | Education | 2023 |
| Nutrition Graduates Ltd | Education | 2025 |
| Nutshell Communications Ltd | Health & social care | 2008 |
| NV HER Limited | Wholesale & retail | 2015 |
| NV IT Services Ltd | Information & communication | 2023 |
| NVK Realty Limited | Real estate | 2026 |
| NW Holdings (Rugby) Limited | Professional & scientific | 2012 |
| NWM Holdings Limited | Professional & scientific | 2000 |
| NWN Enterprises Limited | Professional & scientific | 2012 |
| NX3 Ltd | Real estate | 2020 |
| Nxicon Services Ltd | Information & communication | 2014 |
| Ny&T UK Limited | Manufacturing | 2009 |
| Nyam a Foodz Ltd | Hospitality | 2015 |
| Nøxia Studios Limited | Wholesale & retail | 2026 |
| O H Financial Services Ltd | Financial services | 2026 |
| O'Connor and Costello Properties Ltd | Real estate | 2020 |
| O.L.E Solution Limited | Construction | 2025 |
| O.M.M. Testing Services Limited | Information & communication | 2024 |
| O/D Spares Limited | Professional & scientific | 2011 |
| O1 Inventories Franchising Limited | Administrative & support | 2024 |
| O2 Hyper Health Ltd | Health & social care | 2022 |
| Oabd Inns Limited | Hospitality | 2019 |
| OAH Consulting Limited | Information & communication | 2022 |
| Oairo (Thailand) Limited | Energy | 2015 |
| Oak House Consulting Group (UK) Ltd | Information & communication | 2023 |
| Oaka Vending (West Midlands) Ltd. | Wholesale & retail | 2020 |
| Oakfarm Investments Ltd | Financial services | 2025 |
| Oakland Resources Limited | Professional & scientific | 1970 |
| Oakmoores Interiors Limited | Construction | 2003 |
| Oakpalm Technology Limited | Information & communication | 2014 |
| Oaktree Consultancy Services Limited | Professional & scientific | 2025 |
| Oasis Retail Ltd | Wholesale & retail | 2020 |
| Oates Environmental Limited | Water & waste | 2000 |
| OB1 Goalkeeping Ltd | Wholesale & retail | 2025 |
| Obibok Trans Ltd | Transport & logistics | 2017 |
| Ocean 41 Limited | Hospitality | 2024 |
| Octave Transport Limited | Transport & logistics | 2016 |
| Octavian Coroeanu Ltd | Manufacturing | 2018 |
| Odas Air Ltd | Transport & logistics | 2025 |
| Oddcolours Ltd | Wholesale & retail | 2009 |
| Odyssey Logistics Limited | Transport & logistics | 2020 |
| OFF Cuts Repurposed Ltd | Manufacturing | 2025 |
| OFF Grid Energy Limited | Manufacturing | 2001 |
| Offical Grotto T/A the Christmas Warehouse Ltd | Wholesale & retail | 2020 |
| Officentria Limited | Wholesale & retail | 2025 |
| Offshoreequipment Limited | Wholesale & retail | 2020 |
| OGA Property Limited | Real estate | 2021 |
| Ogea Holdings Ltd | Financial services | 2025 |
| Ogre Wheels Ltd | Wholesale & retail | 2026 |
| OH Mortgages Ltd | Professional & scientific | 2019 |
| OIE Ltd | Information & communication | 2024 |
| Ojas Group Ltd | Information & communication | 2011 |
| OLA Trans Ltd | Administrative & support | 2022 |
| Olaru Gabriel Ltd | Administrative & support | 2017 |
| Old Bell RYE Ltd | Hospitality | 2020 |
| Old House Farm Limited | Real estate | 2026 |
| Old One EYE Tattoo Limited | Other services | 2023 |
| Old Wolston Garage Ltd | Wholesale & retail | 2025 |
| Oldstone Investments Limited | Financial services | 2022 |
| Olectus Ltd | Information & communication | 2025 |
| Oleg Bivol Ltd | Transport & logistics | 2012 |
| OLIFAB34 Limited | Administrative & support | 2019 |
| Olive Store Limited | Wholesale & retail | 2021 |
| Oliwier Trade Ltd | Wholesale & retail | 2023 |
| Olka Ltd | Transport & logistics | 2019 |
| Olka Trans Ltd | Transport & logistics | 2014 |
| Ollivia Foods Ltd | Hospitality | 2023 |
| Ollywood Living Ltd | Real estate | 2025 |
| Olmar 1 Ltd | Transport & logistics | 2016 |
| Oltean Logistics Ltd | Transport & logistics | 2016 |
| OLU and ADE Holdings Limited | Real estate | 2023 |
| Olvara Technologies Limited | Information & communication | 2026 |
| OM Shiv Properties Limited | Real estate | 2026 |
| OM Shree SAI Foods UK Ltd | Hospitality | 2026 |
| Omak Financial Services Ltd | Financial services | 2024 |
| Omerta Riderz Limited | Arts & recreation | 2025 |
| Omni Technologies Limited | Information & communication | 2026 |
| Omnifix Studios Ltd | Wholesale & retail | 2025 |
| Omru Limited | Real estate | 2025 |
| ON Mission INT Ltd | Information & communication | 2023 |
| ON the Bar Solutions Ltd | Manufacturing | 2017 |