| NEM Plant Limited | Construction | 2008 |
| Nero Mafia Limited | Wholesale & retail | 2021 |
| Netlover Ltd | Wholesale & retail | 2026 |
| Neuro Heroes (London) Ltd | Health & social care | 2024 |
| Never Ending Limited | Financial services | 2020 |
| New Beginnings BH Ltd | Professional & scientific | 2025 |
| New Channel Communications Limited | Information & communication | 2016 |
| New Dawn Commercial Limited | Professional & scientific | 1999 |
| New Dawn Inns Limited | Professional & scientific | 2013 |
| New Mode Performance Limited | Wholesale & retail | 2025 |
| Newport Pagnell PT Gym Ltd | Arts & recreation | 2025 |
| Nexus Oak Ltd | Construction | 2020 |
| Nexus QA Ltd | Education | 2024 |
| NH160 Holdings Ltd | Other services | 2026 |
| Nicab Ltd | Manufacturing | 2010 |
| Nick HAY Associates Limited | Professional & scientific | 2020 |
| Nick Smallman Limited | Administrative & support | 2017 |
| Nicklinson Holdings Ltd | Financial services | 2025 |
| Nigel Marvel Engineering Ltd | Professional & scientific | 2019 |
| Nightowl Keyboards Ltd | Manufacturing | 2003 |
| Nimu Services Ltd | Wholesale & retail | 2021 |
| Niuvo UK Limited | Administrative & support | 2025 |
| Nixon & Co Interiors Ltd | Professional & scientific | 2021 |
| NJM Editorial Limited | Professional & scientific | 2011 |
| NJO Consulting Limited | Professional & scientific | 2019 |
| NN12 Composites Limited | Manufacturing | 2024 |
| NO 1 Grill Limited | Hospitality | 2019 |
| NO Visible Bruises CIC | Education | 2026 |
| NON Standard Logic Limited | Wholesale & retail | 2012 |
| Nonna Lucia's Ltd | Hospitality | 2020 |
| NOO HR Ltd | Professional & scientific | 2022 |
| Nordic Snowhow Ltd | Wholesale & retail | 2023 |
| Norfield Consulting Limited | Professional & scientific | 2026 |
| Northampton Auto Programming Limited | Wholesale & retail | 2025 |
| Northampton Digital Ltd | Extraterritorial | 2012 |
| Northampton Event Company Limited | Hospitality | 2023 |
| Northampton Road (Litchborough) Management Company Limited | Extraterritorial | 2012 |
| Northampton Roofing Limited | Construction | 2015 |
| Northampton Tiling Ltd | Construction | 2012 |
| Northamptonshire Therapy Limited | Health & social care | 2025 |
| Northants KOI Limited | Agriculture & fishing | 2014 |
| Northants Tiling Limited | Construction | 2016 |
| Northants Workwear Design & Print Ltd | Wholesale & retail | 2019 |
| Nova Entertainment Services Ltd | Arts & recreation | 2026 |
| Novell Construction Management Ltd | Construction | 2018 |
| Novo Momentum Limited | Professional & scientific | 2025 |
| Novo SPV Limited | Real estate | 2021 |
| Nrvk Limited | Real estate | 2018 |
| NVB Holdings Limited | Professional & scientific | 2017 |
| NWS International Ltd | Transport & logistics | 2022 |
| NZ Balms Ltd | Wholesale & retail | 2025 |
| O'Driscoll Surveys Ltd | Construction | 2023 |
| Oak House Propco Ltd | Financial services | 2026 |
| Oak Woodland Limited | Information & communication | 2015 |
| Oakley Road Developments (Luton) Ltd | Real estate | 2021 |
| Oates & Co (Land) Ltd | Real estate | 2010 |
| Occpsyence Limited | Professional & scientific | 2024 |
| ODD Dog Limited | Information & communication | 2017 |
| ODP Group Ltd | Construction | 2020 |
| Odyssey Wealth Long Term Financial Ltd | Professional & scientific | 2015 |
| Odyssey Wealth Management Ltd | Professional & scientific | 2013 |
| Oesv Limited | Real estate | 2021 |
| Officially Gassed Limited | Information & communication | 2020 |
| OH Catering Ltd | Hospitality | 2026 |
| Olgaf Ltd | Professional & scientific | 2025 |
| Oliphant's Ice Cream & Bakery Ltd | Manufacturing | 2025 |
| Ollie King Limited | Professional & scientific | 2018 |
| Omorfi Nails & Beauty LLP | | 2020 |
| One 2 One Financial Recruitment Limited | Administrative & support | 2005 |
| One Selective Limited | Professional & scientific | 2026 |
| One-Start Limited | Real estate | 2018 |
| Onechef London Ltd | Manufacturing | 2021 |
| Opal Barn Hair & Beauty Ltd | Other services | 2019 |
| OPE Tech Ltd | Information & communication | 2023 |
| Opec Construction Ltd | Construction | 1998 |
| Opec Managed Services Limited | Construction | 2003 |
| Opec Management Services LLP | | 2013 |
| Open Format Technologies Limited | Information & communication | 2022 |
| Open PLM Consulting Ltd | Information & communication | 2009 |
| Operator for Hire Ltd | Administrative & support | 2023 |
| Opes Pakistan Ltd | Wholesale & retail | 2023 |
| Optic Design Limited | Extraterritorial | 2010 |
| Optic Group Limited | Extraterritorial | 2021 |
| Optic Property Ltd | Financial services | 2022 |
| Optic Resourcing Limited | Extraterritorial | 2010 |
| Optiwise Limited | Other services | 2022 |
| ORA Group Ltd | Information & communication | 2020 |
| Orchard Refresh Ltd | Construction | 2023 |
| Orchard Solutions Limited | Professional & scientific | 2019 |
| Original Narratives Ltd | Professional & scientific | 2013 |
| Orion Hotels UK Limited | Professional & scientific | 2011 |
| Osamens Healthcare Ltd | Health & social care | 2023 |
| Oskar's Stylish Homeware Ltd | Wholesale & retail | 2015 |
| Oskarmike Ltd | Wholesale & retail | 2022 |
| Osport Design Limited | Professional & scientific | 2021 |
| OSS Advertising Limited | Extraterritorial | 2021 |
| OSS Media Limited | Information & communication | 2020 |
| OSS Productions Limited | Extraterritorial | 2021 |
| OSS Studios Limited | Extraterritorial | 2021 |
| OT Composites Ltd | Manufacturing | 2026 |