| M J Cale Builders Limited | Construction | 2005 |
| M J Kurton (Electrical) Ltd | Construction | 2014 |
| M J Wilson Management Services Limited | Professional & scientific | 2003 |
| M John Ltd | Real estate | 2024 |
| M Ladbrook Limited | Financial services | 2006 |
| M M & a Investments Ltd | Real estate | 2019 |
| M N P Mijares Endoscopy Ltd | Health & social care | 2023 |
| M N S Superstore Ltd | Wholesale & retail | 2016 |
| M N Stocktaking Services Ltd | Administrative & support | 2003 |
| M P Forks Limited | Wholesale & retail | 2025 |
| M P Leisure Caravans Limited | Wholesale & retail | 2017 |
| M Polovyy Design Ltd | Professional & scientific | 2023 |
| M R J Holding Limited | Real estate | 2016 |
| M S Information & Therapy Centre Ltd. | Health & social care | 1988 |
| M Waugh Haulage Ltd | Transport & logistics | 2025 |
| M Wilce Limited | Manufacturing | 2011 |
| M&C Roof Cleaning Ltd | Administrative & support | 2026 |
| M&G Properties (Cheltenham) Limited | Real estate | 1997 |
| M&K Electric Ltd | Manufacturing | 2012 |
| M&L Stubbs Property Services Ltd. | Real estate | 2016 |
| M&R Reinstatement Ltd | Construction | 2021 |
| M&S Corporation Ltd | Hospitality | 2024 |
| M&S Finance Specialists Ltd | Financial services | 2018 |
| M&S Inns Limited | Hospitality | 2023 |
| M&S Sons Ltd | Health & social care | 2011 |
| M-Tech Design & Manufacture Limited | Manufacturing | 2008 |
| M. N. Petroleum Supplies Limited | Financial services | 1995 |
| M. T. Broady Building Services Limited | Construction | 2006 |
| M.A.M.A. Oral Care Limited | Professional & scientific | 2013 |
| M.B. Auto Electrical Ltd | Wholesale & retail | 2002 |
| M.C. Horrocks Limited | Financial services | 2026 |
| M.D.C Imports (UK) Limited | Wholesale & retail | 2011 |
| M.E. Wynn & Co. Limited | Construction | 1971 |
| M.E.P.L. Limited | Manufacturing | 1996 |
| M.H. Godden Limited | Financial services | 1952 |
| M.J. Loveridge Limited | Construction | 2002 |
| M.K. Flooring (Glos) Limited | Construction | 2025 |
| M.P.J.P. Services Limited | Professional & scientific | 2011 |
| M.P.R (Property and Freelance HGV Services) Ltd | Administrative & support | 2025 |
| M.S. Commercial Services Limited | Wholesale & retail | 2004 |
| M.S. Transport Consultancy Ltd | Transport & logistics | 2022 |
| M2C (Glos) Limited | Administrative & support | 2012 |
| M2M Connect Ltd | Information & communication | 2016 |
| M5 Group Limited | Construction | 2021 |
| M5 Leisure Limited | Wholesale & retail | 2021 |
| M88 Records Ltd | Arts & recreation | 2026 |
| Ma'At Afrika Ltd | Other services | 2023 |
| Mabit Limited | Information & communication | 2024 |
| Mabsco Limited | Health & social care | 2022 |
| MAC Cook Pro Limited | Hospitality | 2018 |
| MAC Madhouse Ltd | Manufacturing | 2023 |
| MACAYE4 Holdings Ltd | Financial services | 2026 |
| Machine Tool Maintenance (Southern) Limited | Manufacturing | 2021 |
| Machinery Development Services Limited | Other services | 1995 |
| Mack Sound Limited | Manufacturing | 2020 |
| Mackenzie Roofing Ltd | Construction | 2025 |
| Macnc Limited | Information & communication | 2014 |
| Macropus Property Management Limited | Real estate | 2007 |
| Made in Knightsbridge Limited | Transport & logistics | 2014 |
| MAE Industrial Trucks Ltd | Wholesale & retail | 2009 |
| Mafatihou Bisri K B Daru CIC | Extraterritorial | 2023 |
| Magedo Ltd | Real estate | 2025 |
| Magenta Principles Limited | Information & communication | 2014 |
| Magnetech Safety Limited | Construction | 2023 |
| Magnetize Consultants Ltd | Information & communication | 2003 |
| Magnum ICC UK Supply Ltd | Manufacturing | 2024 |
| Magon Automotive Limited | Wholesale & retail | 2023 |
| Magpiesalesuk Ltd | Wholesale & retail | 2025 |
| Maguire & Paterson (NI) Limited | Wholesale & retail | 1989 |
| Mahabad Catering Ltd | Hospitality | 2023 |
| Mahat Solutions Ltd | Information & communication | 2015 |
| Mahqam Limited | Hospitality | 2023 |
| Maiga 241 Ltd | Wholesale & retail | 2019 |
| Mainline Civils Limited | Construction | 2021 |
| Mainovate Limited | Construction | 2022 |
| Maisemore Apiaries Limited | Wholesale & retail | 2007 |
| Maison Communications Limited | Extraterritorial | 2018 |
| Maisons Papillon Limited | Real estate | 2017 |
| Majnico Limited | Financial services | 2022 |
| Major Account Sales Limited | Wholesale & retail | 2015 |
| Major Account Sales Services Ltd | Professional & scientific | 2014 |
| Major Agent Ltd | Other services | 2024 |
| Major Building & Civil Engineering Contractors Limited | | 1990 |
| Major Entertainments Limited | Arts & recreation | 2011 |
| Major Roofing Ltd | Construction | 2025 |
| Make a Stand Limited | Agriculture & fishing | 2015 |
| Make Your Marc Consulting Ltd | Information & communication | 2020 |
| Making IT a Success Ltd | Other services | 2018 |
| Makrep E D M Solutions Limited | Manufacturing | 2015 |
| Makrep Holdings Limited | Professional & scientific | 2015 |
| Makrep Limited | Manufacturing | 2003 |
| Malaya Cosmetics Ltd | Wholesale & retail | 2023 |
| Malik Trade House Ltd | Wholesale & retail | 2025 |
| Malloc Limited | Information & communication | 2013 |
| Malloc Properties Limited | Real estate | 2021 |
| Mallu Kitchen Ltd | Hospitality | 2025 |
| Malna Limited | Professional & scientific | 2018 |
| Malvern Aqua Tech Ltd | Construction | 2025 |
| Malvern English Experience Ltd | Education | 2016 |
| Malvern Instruments Ltd | Manufacturing | 2024 |