| Nexia Scientific Limited | Administrative & support | 2011 |
| Nexterra Group Ltd | Information & communication | 2025 |
| Ngdatacomms Limited | Professional & scientific | 2016 |
| NIC Barker Ltd | Other services | 2009 |
| Nice Home Property Renovation Ltd | Professional & scientific | 2022 |
| Nick Baines Construction Ltd | Construction | 2015 |
| Nick Geeson Limited | Construction | 2000 |
| Nick Sims Ltd | Professional & scientific | 2020 |
| Nicola Jane Couture Ltd | Wholesale & retail | 2020 |
| Nikki Woolf Consultancy Services Ltd | Professional & scientific | 2022 |
| Nisa Grocers Limited | Wholesale & retail | 2005 |
| NJK Plumbing and Heating Solutions Limited | Construction | 2024 |
| Nmandco Ltd | Professional & scientific | 2024 |
| NO Nonsense Jobs Limited | Information & communication | 2024 |
| NO. 4 Group Ltd | Other services | 2023 |
| NOBENGAZI24/7 Care Servises Limited | Health & social care | 2011 |
| Noble Synergies Limited | Professional & scientific | 2012 |
| Nobleprint Ltd | Wholesale & retail | 2019 |
| Noliya Investments Ltd | Real estate | 2021 |
| Noor Wholesale Group Ltd | Wholesale & retail | 2026 |
| Northamptonshire Pallets Limited | Manufacturing | 2003 |
| Northgate Ecology Ltd | Professional & scientific | 2025 |
| North’S Car Sales Ltd | Wholesale & retail | 2022 |
| NOT OUT Travel Limited | Administrative & support | 2022 |
| Nottingham University Samworth Academies Trust | Education | 2007 |
| Nova Fitness Coaching Limited | Arts & recreation | 2026 |
| NPS Body Repairs Ltd | Wholesale & retail | 2016 |
| NSC Heating Solutions Limited | Construction | 2010 |
| Nuevo Projects Ltd | Construction | 2021 |
| Nuevo Services Group Ltd | Construction | 2019 |
| Nupsala Group Ltd | Financial services | 2025 |
| Nupsala Limited | Professional & scientific | 2012 |
| Nupsala MSK Clinic Ltd | Professional & scientific | 2024 |
| Nutritium Limited | Extraterritorial | 2010 |
| NYX Performance Limited | Wholesale & retail | 2024 |
| Nzulum Ltd | Information & communication | 2016 |
| O.J. Hallam & SON (Melton Mowbray) Limited | Real estate | 1973 |
| Oakham Developments Limited | Real estate | 2015 |
| Oakham Kitchen Limited | Agriculture & fishing | 2018 |
| Oakham Pest Control Ltd | Professional & scientific | 2019 |
| Oakham Place Limited | Real estate | 1996 |
| Oakham Scaffold Services Ltd | Construction | 2020 |
| Oakley Offset Limited | Manufacturing | 2003 |
| Oaks Financial Limited | Professional & scientific | 2006 |
| Ocean Blue Melton Limited | Hospitality | 2022 |
| OCN Ltd | Professional & scientific | 2022 |
| Old Dalby Church of England Primary School | Education | 2013 |
| Old Station Kennels Limited | Agriculture & fishing | 2024 |
| Ollie Tristram Post - Production Ltd | Information & communication | 2021 |
| Ology Learning Limited | Information & communication | 2025 |
| Omec Ltd | Construction | 2023 |
| Omiteo Limited | Information & communication | 2024 |
| Omni Lifestyle and Fitness Limited | Arts & recreation | 2019 |
| Omniceutica Limited | Extraterritorial | 2010 |
| Omnipakuk Limited | Other services | 2026 |
| One Ceylon Gems Ltd | Wholesale & retail | 2026 |
| One Fire Consulting Ltd | Professional & scientific | 2020 |
| One Story Films Ltd | Information & communication | 2024 |
| Onit Direct Ltd | Manufacturing | 2019 |
| OPF Limited | Financial services | 2018 |
| Ophir 24 Limited | Wholesale & retail | 2023 |
| Ophir Homes Limited | Real estate | 2025 |
| Optimal Media Ltd | Wholesale & retail | 2024 |
| Optimised Fibres International Ltd | Professional & scientific | 2018 |
| Opus Concrete Construction Ltd | Construction | 2025 |
| Opus Eris Limited | Arts & recreation | 2002 |
| Oracle Property Finance Limited | Financial services | 2011 |
| Origin Training & Performance Limited | Arts & recreation | 2025 |
| Oriom Enterprise Ltd | Wholesale & retail | 2025 |
| Orion FM Services Limited | Administrative & support | 2026 |
| Ormond Aircraft Management Ltd. | Transport & logistics | 2009 |
| Ormond Type Training Limited | Professional & scientific | 2023 |
| Orson Bros Ltd | Manufacturing | 2026 |
| Orson FIC Limited | Real estate | 2025 |
| Osborn Construction & Renovation Ltd | Construction | 2014 |
| Osborne Land Ltd | Real estate | 2011 |
| OTG Engineering Ltd | Professional & scientific | 2025 |
| Otsar Group Ltd | Wholesale & retail | 2026 |
| OUR Own Store Limited | Real estate | 2020 |
| Outspoken Clothing Limited | Wholesale & retail | 2016 |
| Overcomers Church Ltd | Education | 2025 |
| Owens Farming Ltd | Agriculture & fishing | 2024 |
| P & a Anderson Limited | Real estate | 2016 |
| P & JK Copley Limited | Agriculture & fishing | 2012 |
| P & K Haulage Limited | Transport & logistics | 2017 |
| P & R Consultants (Twyford) Limited | Professional & scientific | 2015 |
| P a Jones (Ivybridge) LLP | | 2007 |
| P a Jones (Partners) LLP | | 2007 |
| P B Construction (Melton) Limited | Construction | 2014 |
| P C I Installations Limited | Construction | 2003 |
| P Manning Transport Limited | Transport & logistics | 2020 |
| P S R Industrial Limited | Manufacturing | 1989 |
| P&M Structural Design Ltd | Professional & scientific | 2021 |
| P. S. J. Brown Limited | Financial services | 2017 |
| Pagan Treats Limited | Wholesale & retail | 2015 |
| Paint Recycling Limited | Professional & scientific | 2024 |
| PAL Online Consultancy Limited | Information & communication | 2016 |
| Palgorithm Limited | Information & communication | 2024 |
| Pallet Route Solutions Limited | Transport & logistics | 2007 |
| Pannadise Consulting Ltd | Health & social care | 2019 |