| Lydford B Delivery Ltd | Transport & logistics | 2024 |
| Lynn & Andrew Company Limited | Wholesale & retail | 2008 |
| Lyon Fecit Limited | Professional & scientific | 2019 |
| M & J Afzal Estates Limited | Real estate | 2013 |
| M & J Afzal Homes Limited | Real estate | 2018 |
| M & J Afzal Limited | Real estate | 2005 |
| M & N Heating and Plumbing Limited | Construction | 2003 |
| M & P Scott Builders Limited | Construction | 2013 |
| M C Whitton & SON Limited | Construction | 2006 |
| M Castle Coaching Ltd | Professional & scientific | 2026 |
| M Farr Services Ltd | Construction | 2017 |
| M G Decorating Limited | Construction | 2013 |
| M J B General Services Limited | Administrative & support | 2002 |
| M J Cowley Builders Ltd | Construction | 2018 |
| M J Titchmarsh Construction Limited | Construction | 2013 |
| M P Mugford Limited | Construction | 2014 |
| M&B Charles Ltd | Construction | 2023 |
| M&B Vehicle Services Limited | Wholesale & retail | 2021 |
| M&G Hughes Truck Exporters Limited | Transport & logistics | 2002 |
| M&I Logistics Ltd | Transport & logistics | 2013 |
| M&J Logistics Ltd | Transport & logistics | 2025 |
| M-Tech Solutions Constantine Limited | Information & communication | 2025 |
| M. Selby Limited | Construction | 2005 |
| M.B. Speech & Language Therapy Limited | Health & social care | 2011 |
| M.B.G MC Ltd | Wholesale & retail | 2026 |
| M.Curtis Building Ltd | Construction | 2024 |
| M.H. Hall & Sons Limited | Manufacturing | 1988 |
| M.I.C Courier Ltd | Transport & logistics | 2023 |
| M.L. Trailers Limited | Manufacturing | 1987 |
| M.Mumford Electrical Ltd | Construction | 2012 |
| M.S.L Group Worldwide Limited | Financial services | 2020 |
| M77 Race Engineering Limited | Professional & scientific | 2013 |
| MA Robinson Construction Limited | Construction | 2003 |
| Machine Tool Services International Ltd | Professional & scientific | 2022 |
| Made by Brands Ltd | Wholesale & retail | 2018 |
| Madhorofiya Republik Ltd | Arts & recreation | 2020 |
| Madness Cakery Ltd | Manufacturing | 2025 |
| MAE Enterprises Group Ltd | Wholesale & retail | 2026 |
| MAG Equity Evolution Limited | Real estate | 2023 |
| Magna Collocatio Ltd | Hospitality | 2025 |
| Magna Exteriors (Banbury) Limited | Manufacturing | 1996 |
| Magna Exteriors (Liverpool) Limited | Manufacturing | 1998 |
| Magna International Holding (UK) Limited | Manufacturing | 1996 |
| Magni Strength Equipment Limited | Manufacturing | 2022 |
| Mago Creative Ltd | Other services | 2024 |
| Magpie Bay Ltd | Wholesale & retail | 2026 |
| Mahoney and SON Ltd | Construction | 2015 |
| MAK Care Solution Ltd | Health & social care | 2020 |
| Makavid Consulting Limited | Professional & scientific | 2022 |
| Maks Travel Ltd | Transport & logistics | 2015 |
| Malbec Business Services Limited | Professional & scientific | 2007 |
| Malcolm Winyard Limited | Professional & scientific | 2013 |
| Mallard Producktions Ltd | Education | 2021 |
| Mamotive Limited | Financial services | 2021 |
| Management Information Services (UK) Limited | Professional & scientific | 2003 |
| Manchester (Queens Road) Limited | Real estate | 2016 |
| Mane Abode Limited | Other services | 2025 |
| Manning Developments Limited | Real estate | 2023 |
| Manningford Croft Limited | Administrative & support | 2009 |
| Manor Farm (Chipping Warden) Management Company NO. 2 Limited | Other services | 2009 |
| Manor Grove Montessori Limited | Other services | 2008 |
| Manor Surgical Limited | Health & social care | 2018 |
| Manorgate Construction Limited | Construction | 2023 |
| Manorgate Five Limited | Construction | 2021 |
| Manorgate Group Limited | Financial services | 2016 |
| Manov Bioteclinica Limited | Health & social care | 2021 |
| Mansion Hill Ltd | Construction | 2022 |
| Manuel Puro Productions Limited | Information & communication | 1999 |
| Mapatom Limited | Wholesale & retail | 2007 |
| Maple (341) Limited | Real estate | 2008 |
| Maple (435) Limited | Households | 2018 |
| Maple Joinery Services Limited | Construction | 2022 |
| MAR Accountancy Services Ltd | Professional & scientific | 2024 |
| Marc Connor Editing Limited | Information & communication | 2014 |
| Marcel A&B Limited | Transport & logistics | 2020 |
| March Projects Construction Limited | Construction | 2020 |
| March Projects Limited | Construction | 2013 |
| Marine Works Limited | Professional & scientific | 2024 |
| Mariusclincescu Ltd | Transport & logistics | 2022 |
| Mariusluputrans Limited | Transport & logistics | 2018 |
| Mark Anthony Art Finders Ltd | Wholesale & retail | 2025 |
| Mark Ryland Associates Limited | Professional & scientific | 2002 |
| Markham Court (Buckingham) Management Company Limited | Real estate | 1993 |
| Marks Table Limited | Hospitality | 2023 |
| Marlborough Road (Banbury) Residents Limited | Real estate | 2012 |
| Marris Marine Limited | Manufacturing | 2022 |
| Marshall 68 Limited | Hospitality | 2023 |
| Marshall Oakwood Developments Limited | Real estate | 2016 |
| Marshall Supplies Limited | Wholesale & retail | 2013 |
| Marshall TM Ltd | Public administration | 2025 |
| Marshallsay Macari Dixon Limited | Hospitality | 2005 |
| Marston Estates LLP | | 2021 |
| Marston Power Limited | Energy | 2011 |
| Martin Walker Estate Agents Ltd | Real estate | 2009 |
| Martisan Services Ltd | Transport & logistics | 2017 |
| MAS UK Trading Ltd | Wholesale & retail | 2023 |
| Master Kebab House Ltd | Hospitality | 2009 |
| Mastiff Properties Ltd | Real estate | 2020 |
| Mastula Care Ltd | Health & social care | 2017 |
| Material Matters (Oxfordshire) Limited | Households | 2010 |