| Lonsdale Groundwork and Construction Ltd | Construction | 2026 |
| Looma Tech Ltd | Information & communication | 2026 |
| Lostakey Limited | Other services | 2009 |
| Lowe Music Limited | Arts & recreation | 2011 |
| Luxe Meridian Ltd | Wholesale & retail | 2024 |
| Luxury in the Cotswolds Ltd | Hospitality | 2014 |
| Luxury Retreats Ltd | Hospitality | 2020 |
| Lynx 2020 Limited | Professional & scientific | 2019 |
| M a Harrison Ltd | Arts & recreation | 2006 |
| M E Mahlangu Limited | Health & social care | 2019 |
| M&M Real Estate Limited | Real estate | 2021 |
| M. Sykes Limited | Construction | 2003 |
| M.Bradley Metrology Services Limited | Professional & scientific | 2026 |
| MAB Scaffolding Ltd | Construction | 2026 |
| Mabel's Club Limited | Other services | 2022 |
| Machine Link Ltd | Wholesale & retail | 2007 |
| Mackenzie Chapel Ltd | Professional & scientific | 2018 |
| Made by Rene Limited | Manufacturing | 2015 |
| Magda Dreda Pictures Ltd | Information & communication | 2023 |
| Makeup With Madison Ltd | Other services | 2022 |
| Mania Entertainment UK Ltd | Information & communication | 2017 |
| Manor Farm Barns Limited | Households | 1998 |
| Manta Holdings Limited | Other services | 2017 |
| MAP Logic Limited | Information & communication | 2008 |
| Maraterra Ltd | Real estate | 2025 |
| Marhel Management Limited | Professional & scientific | 2009 |
| Maricare Limited | Health & social care | 2003 |
| Mark's Cotswold Bakery Limited | Hospitality | 2018 |
| Marriott Brown Limited | Professional & scientific | 2003 |
| Martin Kealy & Associates Limited | Professional & scientific | 2010 |
| Martin Wills Wildlife Maintenance Trust | Professional & scientific | 2010 |
| Master Express Services Limited | Professional & scientific | 1994 |
| Master Your Transition Ltd | Professional & scientific | 2008 |
| Mastercraft Bodyworks Ltd | Wholesale & retail | 2020 |
| Mattval Properties Limited | Real estate | 2025 |
| Maund Geo-Consulting Limited | Professional & scientific | 2011 |
| Maurice Linehan Racing Limited | Arts & recreation | 2023 |
| Maxwell Douglas Limited | Real estate | 2009 |
| Mcigb Limited | Professional & scientific | 2025 |
| Mcvegas Ltd | Professional & scientific | 2024 |
| Mcwilliam Partners Ltd | Professional & scientific | 2010 |
| Meads Farm Holdings Limited | Agriculture & fishing | 2022 |
| Mecg Limited | Construction | 2008 |
| MED Plus Ltd | Professional & scientific | 2024 |
| Medcopywriter Limited | Professional & scientific | 2012 |
| Mediasmith Marketing Limited | Professional & scientific | 2017 |
| Medical First Limited | Health & social care | 2013 |
| Medical First Properties Limited | Real estate | 2021 |
| Medical Wellness Doctors Ltd | Health & social care | 2025 |
| Medicross Limited | Extraterritorial | 1965 |
| MEGALOMANIACS4U Ltd | Information & communication | 2026 |
| Melanie Jones Associates Ltd | Other services | 2011 |
| Mend Physio Ltd | Extraterritorial | 2011 |
| Merip Consulting Limited | Other services | 2017 |
| Merriscourt Events Limited | Other services | 2012 |
| Meshtex Limited | Manufacturing | 1972 |
| Metos Technologies Ltd | Information & communication | 2023 |
| MEY Designs Limited | Professional & scientific | 2015 |
| Mida Travels Ltd | Transport & logistics | 2024 |
| Middleman Holdings Ltd. | Real estate | 2018 |
| Milbotix Ltd | Professional & scientific | 2020 |
| Milestone Construction Management Limited | Professional & scientific | 2026 |
| Millerick Montgomery Management Ltd | Professional & scientific | 2024 |
| Mindful Mums C.I.C. | Health & social care | 2020 |
| Mintship Limited | Information & communication | 1989 |
| Mitchart Limited | Arts & recreation | 2017 |
| MJ Aviation Solutions Ltd | Manufacturing | 2018 |
| Mobile Projects Ltd | Information & communication | 2017 |
| Mobile Scanning Service Ltd | Other services | 2017 |
| Money Matters Accounting Limited | Professional & scientific | 2021 |
| Monks Park Minerals Limited | Real estate | 2017 |
| Moore and Swain Consulting Ltd | Other services | 2012 |
| Mora Design Ltd | Professional & scientific | 2022 |
| Morgan Inspections Ltd | Professional & scientific | 2022 |
| Morrells Brewery Limited | Professional & scientific | 2008 |
| Morrells Farming Limited | Agriculture & fishing | 2001 |
| Morrells Group Limited | Financial services | 2024 |
| Morrells Holdings Limited | Professional & scientific | 1943 |
| Morris Photographic Centre LP | | 2013 |
| Mosaic Mentality Oxfordshire Community Interest Company | Health & social care | 2025 |
| Mottz Holdings Ltd | Real estate | 2025 |
| Mowbray Media Limited | Professional & scientific | 2012 |
| MPG Local PUB Limited | Hospitality | 2017 |
| MPH Health and Safety Limited | Professional & scientific | 2025 |
| Mprh Limited | Construction | 2026 |
| MPS Media and Editorial Services Ltd | Information & communication | 2025 |
| MR Brands Limited | Wholesale & retail | 2016 |
| MS Locum Consulting Limited | Health & social care | 2023 |
| Mustang-Aholic Ltd | Wholesale & retail | 2023 |
| Mycopro Limited | Health & social care | 2012 |
| Mydanza Ltd | Information & communication | 2024 |
| Mygraduationclip Ltd | Manufacturing | 2022 |
| N Baldwin Services Limited | Construction | 2012 |
| N Dawood Estates Ltd | Real estate | 2020 |
| NA & PA Moulder Limited | Administrative & support | 2012 |
| Naked EYE Studios Limited | Administrative & support | 2020 |
| Narc Interactive Services Ltd | Information & communication | 2015 |
| National Buying Consortium Limited | Administrative & support | 2019 |
| National Distribution Network Limited | Wholesale & retail | 2019 |
| National Response Group Limited | Financial services | 2025 |