| Mowtrade Limited | Wholesale & retail | 2020 |
| Moxy International Ltd | Wholesale & retail | 2025 |
| Moyos Healthcare Ltd | Health & social care | 2019 |
| MPP (Buckingham) Ltd | Administrative & support | 2020 |
| MQT Property Limited | Households | 2026 |
| MR Electrical Lighting Limited | Construction | 2017 |
| MRC Brand Management Ltd | Professional & scientific | 2024 |
| Ms@Cpo Limited | Administrative & support | 2022 |
| Mskubijdh Limited | Health & social care | 2024 |
| Msphere Ltd | Administrative & support | 2008 |
| Msphere Property Ltd | Real estate | 2021 |
| MSV Country Life Limited | Agriculture & fishing | 2019 |
| MTA Pearce Limited | Information & communication | 2018 |
| Mtat Consultancy Limited | Professional & scientific | 2019 |
| MTD Creative Limited | Professional & scientific | 2019 |
| MUD Lane Developments Limited | Construction | 2018 |
| Mulberry Associates Limited | Professional & scientific | 2010 |
| Mulberry Developments Ltd | Construction | 2019 |
| Mulgrave Engineering Limited | Professional & scientific | 2018 |
| Multifold Doors and Windows Limited | Construction | 2016 |
| Mumfudden Suns Ltd | Arts & recreation | 2024 |
| Mummyfit Buckingham and Bicester Ltd | Health & social care | 2025 |
| MW Cooking Ltd | Extraterritorial | 2013 |
| Mwerx Automotive Ltd | Wholesale & retail | 2022 |
| MWM Ardleigh Limited | Water & waste | 2009 |
| My Liberty Care Ltd | Health & social care | 2024 |
| My Style Rocks Boutique Ltd | Wholesale & retail | 2025 |
| MY3TEES Ltd | Health & social care | 2022 |
| Mycore Systems Limited | Information & communication | 2025 |
| N J R Contracts Limited | Construction | 2003 |
| N-Gage Therapeutic Care Group Ltd | Education | 2024 |
| N-Gage Therapeutic Care Ltd | Education | 2022 |
| N. P. Smith Installations Limited | Construction | 2003 |
| Nafisahyg Ltd | Education | 2019 |
| Naikram Consulting Limited | Information & communication | 2010 |
| Nanakaks Tropical Foods Ltd | Hospitality | 2020 |
| Narked Limited | Information & communication | 2000 |
| Nassarammu Medics &Diagnostics Limited | Health & social care | 2023 |
| Natco Foods Limited | Wholesale & retail | 1963 |
| National Brick Events Limited | Wholesale & retail | 2023 |
| National Toy Fair Events Limited | Administrative & support | 2024 |
| Navigator International Limited | Professional & scientific | 2018 |
| Navtech Events Limited | Administrative & support | 2014 |
| NB Consulting Limited | Professional & scientific | 2008 |
| NCA Estates Ltd | Real estate | 2021 |
| NCC Gynaecological Services Ltd | Health & social care | 2023 |
| NDF Investments Limited | Real estate | 2025 |
| Nectus Ltd | Professional & scientific | 2026 |
| Needleway RES Limited | Hospitality | 2026 |
| Neil Bainbridge Engineering Limited | Administrative & support | 2014 |
| Nelson-J Care Ltd | Health & social care | 2015 |
| Network 8 Limited | Information & communication | 2002 |
| Neuralprime Systems Limited | Information & communication | 2025 |
| Neuro-Link Europe Ltd. | Administrative & support | 2014 |
| Neuroadvantage CIC | Administrative & support | 2025 |
| New Drivers LOW Mileage Cars Limited | Wholesale & retail | 2023 |
| New Entrance Limited | Construction | 2016 |
| New Euroline Limited | Transport & logistics | 1991 |
| New Leamington Properties Limited | Real estate | 2025 |
| New Makas Ltd | Other services | 2023 |
| New Records Limited | Information & communication | 2022 |
| New Star Games Limited | Information & communication | 2006 |
| Newbolds Consulting Limited | Information & communication | 2025 |
| Newhook Design Engineering Limited | Professional & scientific | 2012 |
| Nexplan Ltd | Construction | 2024 |
| Nextgen Lions Football Academy Ltd | Education | 2026 |
| NIC Components Europe Limited | Wholesale & retail | 1998 |
| Nicholson Property Investments Ltd | Real estate | 2018 |
| Nicholsons Electrical Ltd | Construction | 2021 |
| Nicu Finte Constructions Ltd | Construction | 2020 |
| Nigel Rand Photography Ltd | Manufacturing | 2024 |
| Nigel Sewell Software Ltd. | Information & communication | 2015 |
| Nine Moons Ltd | Information & communication | 2020 |
| Nipperbout Digital Ltd | Education | 2020 |
| Nipperbout Limited | Health & social care | 2011 |
| Nirmal IT Solutions Ltd | Information & communication | 2023 |
| Nitara London Ltd | Administrative & support | 2017 |
| NMP IT Consultancy Limited | Information & communication | 2025 |
| Noejason's Ltd | Information & communication | 2011 |
| Nomad AI Ltd | Information & communication | 2014 |
| Northampton Wood Flooring Limited | Construction | 2018 |
| Northants Estates Ltd | Real estate | 2023 |
| Novabytepk Limited | Information & communication | 2025 |
| Novel Computing Dynamics Limited | Professional & scientific | 2024 |
| NOW & Then Theatre Company Limited | Arts & recreation | 2019 |
| NRB IT Services Limited | Information & communication | 2010 |
| NRB ITS Holdings Limited | Information & communication | 2024 |
| Nsar-Tech Ltd | Information & communication | 2020 |
| Nudj Tech Limited | Information & communication | 2020 |
| Nunc Living Limited | Manufacturing | 2019 |
| Nurture & Grow Forest & Play Ltd | Health & social care | 2026 |
| Nury Ltd | Information & communication | 2025 |
| Nutrigenics Ltd | Health & social care | 2019 |
| NXT Level Coaching Ltd | Education | 2020 |
| O&C Ventures Ltd | Wholesale & retail | 2024 |
| O'Dell Building Services Ltd | Construction | 2019 |
| O'Dell Construction & Carpentry Ltd | Manufacturing | 2026 |
| Oaker Limited | Professional & scientific | 2009 |
| Oakes Tools Limited | Manufacturing | 1985 |
| Oakpark Alarms Security Services Limited | Public administration | 2002 |