| Metal Box Pension Trustees Limited | Other services | 1979 |
| MEW Therapy Limited | Health & social care | 2012 |
| MG Helicopters Limited | Administrative & support | 2017 |
| Micronanics Limited | Manufacturing | 2009 |
| Midline Limited | Professional & scientific | 2020 |
| Mike Hannaby Financial Planning Ltd | Professional & scientific | 2020 |
| Milton Hill Skin Clinic and Day Spa Ltd | Other services | 2016 |
| MINDHEALTH360 Limited | Other services | 2018 |
| Minerva Medical Aesthetics Limited | Health & social care | 2018 |
| Misali Island Limited | Real estate | 2021 |
| Mission 4 Nutrition Limited | Health & social care | 2016 |
| Mission Community (Wantage) Ltd | Professional & scientific | 2023 |
| Mission Group (Wantage) Ltd | Financial services | 2023 |
| Mission Motorsport | Arts & recreation | 2011 |
| Mission Motorsport Trading Ltd | Arts & recreation | 2006 |
| Mitcham Viticultural Services Ltd | Agriculture & fishing | 2019 |
| MJA Resources Ltd | Extraterritorial | 2020 |
| Mjcforkrentuk Limited | Administrative & support | 2016 |
| MJK Construction & Development Ltd | Construction | 2017 |
| MKM I.T Solutions Ltd | Information & communication | 2025 |
| Modern Vibe Ltd | Wholesale & retail | 2023 |
| Molaes Training and Consulting Ltd | Professional & scientific | 2017 |
| Momenta Training Limited | Administrative & support | 2019 |
| Mongewell Court Residents Limited | Households | 2005 |
| Monkton House Management Company Limited | Households | 1983 |
| Montcalm International Limited | Wholesale & retail | 2004 |
| Monterra Consulting Ltd | Professional & scientific | 2025 |
| Moorhen Media Ltd | Information & communication | 2021 |
| Mortise and Tenon Limited | Construction | 2019 |
| Moss Corporation Limited | Professional & scientific | 2025 |
| Motionblast Ltd | Information & communication | 2007 |
| Motorhub Services Wantage Ltd | Wholesale & retail | 2026 |
| Motorlux Ford Limited | Wholesale & retail | 2024 |
| Motorlux Ltd. | Wholesale & retail | 2009 |
| Movevu Ltd | Extraterritorial | 2014 |
| Mowahead Garden Maintenance Limited | Administrative & support | 2025 |
| Mpconsult Limited | Wholesale & retail | 2016 |
| MRF Innovations Limited | Manufacturing | 2013 |
| MRT Financial Planning Limited | Financial services | 2025 |
| MSM Coaching Limited | Professional & scientific | 2008 |
| MSR Homecare Birmingham Limited | Health & social care | 2025 |
| Multi Risk Solutions Limited | Financial services | 2012 |
| Muster Point Campsite Ltd | Hospitality | 2019 |
| MUT Ltd | Health & social care | 2022 |
| Mutatio Group Ltd | Wholesale & retail | 2025 |
| MV37 Ltd | Information & communication | 2017 |
| MW Structural Designs Ltd | Professional & scientific | 2020 |
| Mybp Ltd | Information & communication | 2009 |
| Myst Lifestyle Ltd | Wholesale & retail | 2023 |
| N & M Electrical Limited | Construction | 2008 |
| N&G Contracts Ltd | Construction | 2025 |
| N&G Projects Ltd | Construction | 2024 |
| Naldertown Holdings Limited | Financial services | 2022 |
| Nature Scale Limited | Information & communication | 2023 |
| Navtech Radar Limited | Information & communication | 1999 |
| NAYMAT130 Ltd | Administrative & support | 2024 |
| Nelson Roofing and Building Ltd | Construction | 2007 |
| Nelson Travel Ltd | Administrative & support | 2021 |
| NET Zero Foundation | Health & social care | 2019 |
| Netkind Consultants Ltd | Professional & scientific | 2025 |
| Netspire Ltd | Information & communication | 2025 |
| Network Security Integrations Ltd | Information & communication | 2020 |
| New Venture Products Limited | Wholesale & retail | 2003 |
| Newmarkhome Ltd | Manufacturing | 2023 |
| Newmarshell Ltd | Real estate | 2024 |
| Nextorn Ltd | Information & communication | 2025 |
| Ng-It Solutions Ltd | Information & communication | 2019 |
| NHC Newbury Ltd | Health & social care | 2024 |
| Nickless Technologies Limited | Professional & scientific | 2018 |
| Nicola Parkin Design Limited | Other services | 2015 |
| NIH Clinics Limited | Health & social care | 2011 |
| NIH Healthcare Limited | Health & social care | 2016 |
| NIH Management Limited | Health & social care | 2016 |
| Nin's Plant Nursery Ltd | Professional & scientific | 2012 |
| Nine Months of Style Ltd | Wholesale & retail | 2024 |
| Nippy Ltd | Transport & logistics | 2022 |
| NJC Education Consultancy Limited | Education | 2016 |
| Njcjoinery Ltd | Manufacturing | 2011 |
| NO Water Just Shine Oxford Limited | Administrative & support | 2024 |
| Nomadic Property Partners Ltd | Real estate | 2026 |
| None of the Above Limited | Professional & scientific | 2024 |
| Nookbooks Ltd | Information & communication | 2026 |
| Nordic Glamping Ltd | Manufacturing | 2018 |
| Norris Carpentry and Building Services Limited | Manufacturing | 2019 |
| North Farm Estates Limited | Real estate | 1957 |
| North Farm Stud Ltd | Agriculture & fishing | 1998 |
| North Rona LLP | | 2008 |
| Notecom Limited | Information & communication | 2004 |
| Nourishing Connections Ltd | Health & social care | 2021 |
| Noviun Surfaces Limited | Construction | 2024 |
| NOW Exhale Ltd | Other services | 2025 |
| NRG Tech Ltd | Energy | 2023 |
| NS Integrations Limited | Extraterritorial | 2026 |
| NS Intelligence Holdings Ltd | Professional & scientific | 2017 |
| NS Intelligence IP Ltd | Professional & scientific | 2017 |
| Nuclear Consulting Limited | Professional & scientific | 2010 |
| Nur(Uk) Limited | Hospitality | 2014 |
| NXN Partners Limited | Information & communication | 2025 |
| OA Nguyen-Smith Ltd | Information & communication | 2023 |
| Oak Leaf Tree Services Limited | Professional & scientific | 2003 |