| MHF Global Ltd | Transport & logistics | 2026 |
| MHH (Oxford) Limited | Professional & scientific | 2019 |
| MHS Principal Limited | Real estate | 2021 |
| MI Casa Developments Ltd | Construction | 2023 |
| MI Dogar Limited | Wholesale & retail | 2021 |
| MI Retailer Mart Ltd | Wholesale & retail | 2024 |
| MIA Consultants Ltd | Professional & scientific | 2026 |
| Miakat Ltd | Administrative & support | 2016 |
| Miakos Ltd | Professional & scientific | 2014 |
| MIAN365BUSINESS Ltd | Wholesale & retail | 2025 |
| Micas Simulations Limited | Information & communication | 2004 |
| Michael & Megan Dent Ltd | Professional & scientific | 2020 |
| Michael Butler Construction Limited | Construction | 2005 |
| Michael Duffy Property Maintenance Limited | Construction | 2014 |
| Michael Earnest Productions Ltd | Information & communication | 2020 |
| Michael Silva Oxford Surgery Limited | Health & social care | 2016 |
| Michala's Creatives Ltd | Professional & scientific | 2019 |
| Mick Partlett Car Sales Limited | Wholesale & retail | 2005 |
| Mick&Sons Ltd | Construction | 2008 |
| Micromelt Ltd | Professional & scientific | 2023 |
| Microsharp Innovation Limited | Manufacturing | 2013 |
| Microsonic Solutions Ltd | Information & communication | 2017 |
| Midas Automotive Ltd. | Manufacturing | 2009 |
| Middle Farm Livery Ltd | Agriculture & fishing | 2023 |
| Middle Friday Ltd | Administrative & support | 2017 |
| Middle Way Trust | Health & social care | 2021 |
| Middlebury College UK Trust Limited | Education | 2000 |
| Middleway Catering Ltd | Hospitality | 2020 |
| Mide Development Limited | Professional & scientific | 2024 |
| Midenas Limited | Health & social care | 2019 |
| Midnight Alpaca Limited | Agriculture & fishing | 2025 |
| Midwinter Freehold Limited | Households | 2004 |
| Midwinter Limited | Professional & scientific | 1993 |
| Midwinter Residents Association Limited | Households | 1991 |
| Mietek-Ideas Factory Ltd | Construction | 2017 |
| Mighty Bites Ltd | Hospitality | 2023 |
| Mighty Fine Oaks Ltd | Agriculture & fishing | 2025 |
| Migrate UK Ltd | Professional & scientific | 2004 |
| Migzzy Official Limited | Manufacturing | 2022 |
| Mihai Housing Ltd | Real estate | 2018 |
| Mihai Medical Ltd | Health & social care | 2015 |
| Mikbasket Ltd | Wholesale & retail | 2026 |
| Mike ADY Limited | Professional & scientific | 2015 |
| Mike Morgan Limited | Real estate | 2020 |
| Mike Wilford Associates Limited | Professional & scientific | 2023 |
| Miki Clothing Ltd | Wholesale & retail | 2025 |
| Miko Building Services Ltd | Construction | 2015 |
| Mikohn Europe B.V. | | 2005 |
| Mikra Ltd | Manufacturing | 2021 |
| Mila UK Cleaning Services Limited | Other services | 2007 |
| Milan Capital Limited | Real estate | 2022 |
| Miles Better Valeting Limited | Other services | 2024 |
| Miles Properties London Limited | Real estate | 2019 |
| Milia WH Ltd | Real estate | 2023 |
| Milio Limited | Wholesale & retail | 2018 |
| Military Policy Research Limited | Information & communication | 1996 |
| Mill View Garden Centre Limited | Wholesale & retail | 2010 |
| Millar Cameron Ltd | Administrative & support | 2007 |
| Millbank Residents Company Ltd | Households | 1995 |
| Millbox CNC Limited | Administrative & support | 2025 |
| Millduce Limited | Extraterritorial | 1945 |
| Millenis UK Limited | Wholesale & retail | 1994 |
| Miller Bayliss Ltd | Real estate | 2023 |
| Miller Health Management LLP | | 2024 |
| Millhill Tools (Warehousing) Limited | Transport & logistics | 1985 |
| Mills Transport Limited | Transport & logistics | 2005 |
| Millstream Court Residents Association Limited | Real estate | 1983 |
| Milo GAS Ltd | Construction | 2020 |
| Milodowski Consulting Ltd | Professional & scientific | 2024 |
| Milton Direct Limited | Wholesale & retail | 2024 |
| Milton Manor Drive Residents Association (1971) Limited | Other services | 1971 |
| Milton Service Station Limited | Wholesale & retail | 1992 |
| Milvus Consulting Ltd | Professional & scientific | 2022 |
| Mima-Uk Limited | Other services | 1985 |
| Mimesis Innovation Enterprise Ltd | Professional & scientific | 2024 |
| Mimi Healthcare Services Ltd | Health & social care | 2016 |
| Mimick Limited | Wholesale & retail | 2025 |
| MIN Healthcare Corporations Ltd | Administrative & support | 2022 |
| Mind and Planet Ltd | Information & communication | 2022 |
| Mind Foundry Limited | Information & communication | 2015 |
| Mind Over Matter Fitness Centre Ltd | Arts & recreation | 2026 |
| Mindery AI Limited | Information & communication | 2025 |
| Minds on Growth Ltd | Health & social care | 2025 |
| Mindspiration Ltd | Wholesale & retail | 2021 |
| Minervation Limited | Information & communication | 2001 |
| Minghe Commercial Co. Ltd | Hospitality | 2013 |
| Minghe Property Limited | Hospitality | 2024 |
| Ministry of Oak&Hardwood Ltd | Construction | 2025 |
| Minns (Oxford) Limited | Real estate | 1956 |
| Minns Consulting Limited | Professional & scientific | 1996 |
| Minns Development Management Limited | Construction | 2003 |
| Minns Estates Limited | Construction | 1982 |
| Minoli & Company Limited | Wholesale & retail | 1960 |
| Minox Trading Limited | Wholesale & retail | 2013 |
| Minshell Designs Ltd | Professional & scientific | 2021 |
| Mintmill Headington Ltd | Hospitality | 2025 |
| Mintmist Limited | Professional & scientific | 2003 |
| Minty (Furniture) Limited | Wholesale & retail | 2009 |
| Minty (Oxford) Limited | Wholesale & retail | 2002 |
| Minu Payment Solutions UK Ltd | Financial services | 2025 |