| Marxle Limited | Construction | 2015 |
| Mary Zhou Properties Ltd | Real estate | 2025 |
| Maryam Health Care Services Limited | Health & social care | 2018 |
| Masda Ltd | Professional & scientific | 2020 |
| Mash Properties Ltd | Financial services | 2018 |
| Masha Trading Limited | Wholesale & retail | 2015 |
| Masih & Stars Ltd | Information & communication | 2025 |
| Mason Commercial Cleaning Limited | Administrative & support | 2016 |
| Masooda Ltd | Information & communication | 2018 |
| Massaya Oxford Ltd | Hospitality | 2024 |
| Mast Instruments Ltd | Wholesale & retail | 2022 |
| Master Butcher Oxford Ltd | Wholesale & retail | 2025 |
| Masterkey Consultancy Ltd | Professional & scientific | 2025 |
| Mastrandrea Consulting Limited | Extraterritorial | 2013 |
| MAT Builders Ltd | Construction | 2019 |
| Matay Consulting Ltd | Information & communication | 2019 |
| Match Consultants Ltd | Administrative & support | 2006 |
| Matchless Limited | Manufacturing | 2017 |
| Matchtrips Limited | Administrative & support | 2025 |
| Material-Sim Engineering Ltd | Professional & scientific | 2024 |
| Materialogic Ltd | Professional & scientific | 2020 |
| Mates Rates Comedy Ltd | Arts & recreation | 2020 |
| Matex Sporting Intelligence Ltd | Information & communication | 2025 |
| Mathemetrics Limited | Information & communication | 2001 |
| Mathom Ltd | Wholesale & retail | 2025 |
| Maths Mastery Limited | Education | 2022 |
| Matick Realty Ltd | Wholesale & retail | 2025 |
| Matina Services Limited | Wholesale & retail | 2021 |
| Matt B & H Limited | Construction | 2024 |
| Matt Todd Enterprises Ltd | Professional & scientific | 2022 |
| Mattarth Ltd | Professional & scientific | 2019 |
| Matter PR Limited | Professional & scientific | 2015 |
| Matthew Duggan Associates Limited | Administrative & support | 2011 |
| Matthew Ellacott Creative Solutions Limited | Information & communication | 2019 |
| Mattingly Building Engineering Services Limited | Construction | 2011 |
| Matty Cars Limited | Transport & logistics | 2026 |
| Maull Surveyors Limited | Professional & scientific | 2023 |
| Mavra Advertising Ltd | Professional & scientific | 2013 |
| Mawa Oxford Ltd | Hospitality | 2025 |
| MAX Food Limited | Wholesale & retail | 2006 |
| Maximise IT Wellbeing CIC | Health & social care | 2025 |
| Maximised Programming Solutions Limited | Information & communication | 2020 |
| MAY Morning Limited | Construction | 2025 |
| Maya's Coffee Limited | Hospitality | 2022 |
| Mayfair Windows and Doors Limited | Manufacturing | 2026 |
| Mayfield Corporate Ventures Limited | Professional & scientific | 2013 |
| Mayfield Partners | Administrative & support | 2009 |
| Mayfield Press Partners LLP | | 2019 |
| Mayhew-Archer Limited | Information & communication | 2001 |
| Mayo Digital Media Limited | Information & communication | 2015 |
| Maythorn Property Ltd | Real estate | 2025 |
| MAZ Business Consultants Ltd | Professional & scientific | 2024 |
| Mazo Catering Ltd | Hospitality | 2018 |
| MB & Sorna Investment Ltd | Real estate | 2026 |
| MB International Apparel Ltd | Manufacturing | 2022 |
| MB Optometry Ltd | Wholesale & retail | 2020 |
| MB VAT Services Limited | Professional & scientific | 2020 |
| MBA Affiliation Ltd | Professional & scientific | 2012 |
| MBC (Estates) Limited | Agriculture & fishing | 1995 |
| MBJ Developments Ltd | Real estate | 2020 |
| MBN Food Limited | Hospitality | 2024 |
| Mbowen Medical Practice Ltd | Professional & scientific | 2023 |
| Mbtk Scientific Consultants Limited | Professional & scientific | 2018 |
| Mbuy Global Ltd | Wholesale & retail | 2023 |
| MC Racing Limited | Arts & recreation | 2026 |
| MC Social Media Marketing Ltd | Professional & scientific | 2026 |
| MC1 Productions Ltd | Information & communication | 2018 |
| Mccann Ltd | Information & communication | 2022 |
| Mccarthy Developments Ltd | Real estate | 2022 |
| Mccarthy Madsen Limited | Wholesale & retail | 2015 |
| Mccarthy Marketing Ltd | Professional & scientific | 2025 |
| Mccdesign Holdings Limited | Professional & scientific | 2008 |
| Mccracken & Sons Limited | Administrative & support | 2006 |
| Mcdonagh & Son’S Properties Ltd | Real estate | 2023 |
| Mcdonald Goble Limited | | 1963 |
| MCE6 Limited | Hospitality | 2026 |
| Mcgill Advisory Ltd | Professional & scientific | 2025 |
| Mcgowan Sensor Labs Limited | Professional & scientific | 2009 |
| MCH Construction Oxford Ltd | Construction | 2021 |
| Mchex Cyber Pulse Ltd | Construction | 2024 |
| Mckenzie Paving & Landscaping Ltd | Construction | 2020 |
| Mclellan Management Limited | Households | 2003 |
| Mcneill Mathematics Consultancy Limited | Education | 2009 |
| Mcneill Plastering Limited | Construction | 2020 |
| Mcnulty Investments Limited | Real estate | 2020 |
| MCS Asset Management Limited | Real estate | 2000 |
| MD Construction Ltd | Construction | 2018 |
| MD Live Ltd | Health & social care | 2015 |
| MD Pizza Co Limited | Hospitality | 2023 |
| MD S I Ltd | Information & communication | 2016 |
| Mdkodm Global Limited | Financial services | 2018 |
| MDS Real Estate Ltd | Real estate | 2022 |
| Meadow Portfolio One Limited | Real estate | 2021 |
| Meadow Portfolio Three Limited | Real estate | 2024 |
| Meadow Portfolio Two Limited | Real estate | 2021 |
| Meadow View Freehold Company Limited | Households | 2020 |
| Meadow View Wheatley Management Company Limited | Households | 1994 |
| Meadowrk Limited | Real estate | 2021 |
| Meadsale Limited | Professional & scientific | 1997 |
| Meal Plus Ltd | Hospitality | 2022 |