| Magda Bouwman Limited | Health & social care | 2023 |
| Magic Badger Limited | Financial services | 2018 |
| Magna Cleaning Services Ltd | Administrative & support | 2022 |
| Magnaissance Limited | Professional & scientific | 2024 |
| Mallams Estate Agency Limited | Real estate | 2008 |
| Mallams Limited | Other services | 1997 |
| MAN Walks Into a PUB Limited | Hospitality | 2024 |
| Manarin Ltd | Transport & logistics | 2014 |
| Manor Court (Carterton) Management Company Limited | Households | 1986 |
| Manor Court Management Association (Oxford) Limited | Households | 1977 |
| Manor Ground Oxford Limited | Professional & scientific | 2005 |
| Manor Park (London Road) Management Company Limited | Households | 2003 |
| Mark Kenyon Television Lighting Design Limited | Administrative & support | 1997 |
| Mark Smith & Co. Limited | Wholesale & retail | 1998 |
| Marlborough Place (Woodstock) Flats Management Company Limited | Households | 2010 |
| Marshalls Surveyors Limited | Professional & scientific | 2015 |
| Marston Ferry Court (Oxford) Management Company Limited | Households | 1981 |
| Martin Close Management Company Limited | Households | 2013 |
| Martin Court (RTM) Company Limited | Households | 2013 |
| Matrix Magnets Ltd | Manufacturing | 2009 |
| Matthew Ginks Ltd | Health & social care | 2018 |
| Matthew James Building Maintenance & Conservation Ltd | Construction | 2021 |
| MAX Duncan Ltd | Information & communication | 2019 |
| Mccalmon Roofing Limited | Construction | 2015 |
| MCF Sports Ltd | Other services | 2016 |
| Mcinter Property Ltd | Real estate | 2024 |
| MCJ Builders Ltd | Construction | 2025 |
| Meadow Walk Limited | Households | 2019 |
| Meccanica Engineering Limited | Professional & scientific | 2019 |
| Medoxpro International Limited | Information & communication | 2023 |
| Mellonia Property Limited | Real estate | 2018 |
| Meltz Limited | Hospitality | 2002 |
| Merryhall Construction Ltd | Construction | 2024 |
| Metalwoode Manufacturing Limited | Manufacturing | 2025 |
| Metier Repower Limited | Manufacturing | 2023 |
| Metier Technologies Limited | Manufacturing | 1984 |
| Metier Ventures Limited | Professional & scientific | 2022 |
| Metrology Direct Limited | Administrative & support | 2015 |
| Mezzanine Digital Ltd | Professional & scientific | 2025 |
| MFM Courier Ltd | Transport & logistics | 2018 |
| MGM Couriers Ltd | Transport & logistics | 2020 |
| MHL Ltd | Construction | 2013 |
| Microtechnica Limited | Administrative & support | 2009 |
| Midsummer Developments Ltd | Construction | 2026 |
| Migg Inns Ltd | Hospitality | 2022 |
| Miglico Rentals Limited | Real estate | 2025 |
| Milford House Management Company (Oxford) Limited | Households | 2004 |
| Milham Place Management Company Limited | Households | 2002 |
| Millers Cottages Residents Management Company Limited | Households | 2014 |
| Millers Mews (Witney) Management Company Limited | Households | 1997 |
| Mind Farm Holdings Limited | Financial services | 2026 |
| Mini Professionals Dance Academy Ltd | Arts & recreation | 2016 |
| Miniyap Consultancy Limited | Manufacturing | 2012 |
| Mirrorfield Ltd | Information & communication | 2024 |
| Mister IT Limited | Information & communication | 2008 |
| MIX Beauty's HB Ltd | Other services | 2023 |
| MJ & Associates Ltd | Information & communication | 2019 |
| Mldt Ltd | Other services | 2025 |
| Mlpt Limited | Arts & recreation | 2022 |
| Mmuk Singh Ltd | Wholesale & retail | 2025 |
| MNS Properties Development Ltd | Construction | 2025 |
| Modern Shortlets Limited | Hospitality | 2018 |
| Mohidul Ltd | Hospitality | 2019 |
| Momentum Aviation Limited | Transport & logistics | 2023 |
| Mondi's Properties Ltd | Real estate | 2024 |
| Mont Meru Limited | Arts & recreation | 2002 |
| Moors Construction Ltd | Construction | 2012 |
| Morland Court (Abingdon) Limited | Households | 1986 |
| Mortimer Court (Oxford) Management Company Limited | Households | 2015 |
| Mosiox Ltd | Real estate | 2025 |
| Motus VR Limited | Manufacturing | 2021 |
| Mount House Management Limited | Households | 2021 |
| Mountbatten Limited | Construction | 2000 |
| Mountmorris Developments Ltd | Construction | 2011 |
| MP3TRAVELCLUB.COM Ltd | Professional & scientific | 2001 |
| Mppm Bristol Limited | Financial services | 2022 |
| MQ Property Co Limited | Real estate | 2018 |
| Mrcc Limited | Professional & scientific | 2023 |
| MRD Rendering Services Ltd | Construction | 2018 |
| Mrfc Ltd | Construction | 2012 |
| Mulberry Court (Kidlington) Management Company Limited | Households | 2012 |
| Mulberry Court Oxford Limited | Households | 2010 |
| Mulder Property Holdings Limited | Real estate | 2026 |
| Multi-Floors Limited | Construction | 1962 |
| Multilingual Translation and Interpreting Ltd | Professional & scientific | 2005 |
| Murray Court (Oxford) Freehold Limited | Households | 2002 |
| MVN Technologies Limited | Information & communication | 2015 |
| My Magic Lotto Limited | Administrative & support | 2021 |
| Myheli Ltd | Professional & scientific | 2017 |
| Myrtle Farm Court (Long Hanborough) Residents Company Limited | Households | 2016 |
| N P Smith Limited | Professional & scientific | 2013 |
| Nano Circuit Limited | Wholesale & retail | 2025 |
| Nasaba Limited | Real estate | 2017 |
| Nasha Holdings Limited | Information & communication | 2018 |
| Nassupplied Ltd | Wholesale & retail | 2026 |
| Nature Works Limited | Health & social care | 1984 |
| NBT Fired Clay Limited | Professional & scientific | 2008 |
| Ndege Aviation Ltd | Administrative & support | 2023 |
| Nekton Foundation | Information & communication | 2015 |
| Neojoy Ltd | Wholesale & retail | 2017 |