| M S Displays Limited | Professional & scientific | 2009 |
| M Shaw Ltd | Administrative & support | 2023 |
| M T Kerala Ltd | Wholesale & retail | 2022 |
| M Truswell Ltd | Construction | 2016 |
| M Tuck Roofing Services Ltd | Construction | 2017 |
| M Willgoose Properties Ltd | Real estate | 2019 |
| M Williams Ltd | Professional & scientific | 2022 |
| M&D 4 Catering Ltd | Hospitality | 2024 |
| M&E Care Limited | Health & social care | 2014 |
| M&H Tech Ltd | Wholesale & retail | 2023 |
| M&K Groundworks and Civils Ltd | Construction | 2025 |
| M&R Plastering and Building Contractors Ltd | Construction | 2025 |
| M. Collings Limited | Wholesale & retail | 2015 |
| M. J. D. (Mansfield) Limited | Construction | 2005 |
| M. Stevenson Transport Ltd | Transport & logistics | 2022 |
| M. Wilkinson Limited | Agriculture & fishing | 2006 |
| M.A.N Shelters Limited | Water & waste | 2003 |
| M.A.Shaw Ltd | Other services | 2019 |
| M.Draycott Contracting Ltd | Construction | 2024 |
| M.E.D. Mobile JET Cleaning Limited | Administrative & support | 2014 |
| M.F. Transport (Chesterfield) Limited | Transport & logistics | 2008 |
| M.G. Walker & Co. Limited | Professional & scientific | 2003 |
| M.J.Orton Ltd. | Extraterritorial | 2024 |
| M.N Recycling Solutions Limited | Water & waste | 2016 |
| M.P.D Services Ltd | Transport & logistics | 2007 |
| M.R. Kent Ltd | Transport & logistics | 2019 |
| M.T.M. Products (Industrial Screen Process Printers) Limited | Manufacturing | 1976 |
| M1 Car Sales Limited | Wholesale & retail | 2025 |
| M1 Kennels Ltd | Wholesale & retail | 2021 |
| M1 Scaffolding JCT 29A Limited | Construction | 2016 |
| M2 Construction & Development Ltd | Construction | 2004 |
| MA Land and Properties Limited | Real estate | 2017 |
| Mabel & Co Properties Ltd | Real estate | 2021 |
| Mabgate Property Management Ltd | Wholesale & retail | 2024 |
| MAC Tools (Chesterfield) Limited | Wholesale & retail | 2017 |
| Macarthur Homes Limited | Construction | 2023 |
| Macclesfield Toys Limited | Wholesale & retail | 2016 |
| Macgregor Projects Ltd | Construction | 2022 |
| Machen Construction Ltd. | Construction | 2002 |
| Machinery Appraisal Services Ltd | Financial services | 2019 |
| Mackrell Properties Ltd | Real estate | 2024 |
| Maclott Brickwork Ltd | Construction | 2021 |
| Macnele Care Services Limited | Health & social care | 2023 |
| Macpeg Electrical Systems Ltd | Construction | 2020 |
| MAD Architects LLP | | 2006 |
| MAD Bars Limited | Hospitality | 2022 |
| MAD Hatter Motors Ltd | Wholesale & retail | 2020 |
| MAD Signs & Graphics Limited | Administrative & support | 2015 |
| MAD Zebra Limited | Professional & scientific | 2026 |
| Madagascar Zebra Limited | Wholesale & retail | 2026 |
| Madden Transport Limited | Transport & logistics | 2018 |
| Maddox Properties Limited | Real estate | 2021 |
| Made by Law Ltd | Professional & scientific | 2021 |
| Made by Marketing Ltd | Professional & scientific | 2024 |
| MAG Chesterfield Properties Limited | Real estate | 2023 |
| Magbroach (UK) Limited | Manufacturing | 1999 |
| Magdalene Gardens Management Company Limited | Households | 2016 |
| Magic of Bengal Ltd | Hospitality | 2019 |
| Magical Clubs Berkshire Limited | Education | 2019 |
| Magical Clubs Buckinghamshire Limited | Education | 2022 |
| Magical Clubs Hertfordshire Limited | Education | 2015 |
| Magical Moments Soft Play & Party Hire Ltd | Health & social care | 2025 |
| Magmatronics Ltd | Manufacturing | 2010 |
| Magna Homecare Limited | Public administration | 2019 |
| Magnavale Chesterfield Ltd | Manufacturing | 1989 |
| Magnavale Easton Ltd | Manufacturing | 2022 |
| Magnavale Holdings Limited | Manufacturing | 2020 |
| Magnavale Limited | Manufacturing | 2013 |
| Magnavale Properties Limited | Transport & logistics | 2014 |
| Magnavale Scunthorpe Ltd | Manufacturing | 2010 |
| Magnavale Southwest Holdings Limited | Financial services | 2022 |
| Magnavale Southwest Operations 1 Limited | Transport & logistics | 2022 |
| Magnavale Southwest Operations 2 Limited | Manufacturing | 2024 |
| Magnavale Southwest Properties Limited | Real estate | 2022 |
| Magnavale Warrington Ltd | Manufacturing | 2015 |
| Magnifica Technologies Ltd | Wholesale & retail | 2013 |
| Magnumart Ltd | Other services | 2024 |
| Magpie Beauty Holdings Limited | Real estate | 2017 |
| Magpie Beauty Limited | Wholesale & retail | 2015 |
| Magpie Operations Ltd | Administrative & support | 2026 |
| Maik F.M Ltd | Administrative & support | 2007 |
| Mailworld Limited | Manufacturing | 2013 |
| Main Enterprises Ltd | Wholesale & retail | 2020 |
| Maize Garden Ltd | Hospitality | 2026 |
| Major Demand Limited | Administrative & support | 2022 |
| Major Savings Limited | Extraterritorial | 2014 |
| Makesconsense Ltd | Administrative & support | 2019 |
| Makh Beauty Ltd | Other services | 2024 |
| Malc Walker Truck Training Ltd | Education | 2013 |
| Malcolm Needham & Co Limited | Professional & scientific | 2004 |
| Mallinckrodt Chemical Holdings (U.K.) Limited | Professional & scientific | 1992 |
| Mallinckrodt Chemical Limited | Manufacturing | 1987 |
| Mallinder Properties Limited | Construction | 2005 |
| Mallott Construction Limited | Construction | 2013 |
| Mallu Ventures (UK) Ltd | Construction | 2024 |
| Malyon Developments Ltd | Construction | 2017 |
| Mamababa Care Company Limited | Manufacturing | 2026 |
| Mamaccino Ltd | Professional & scientific | 2018 |
| Mamma Marriotts Catering Limited | Hospitality | 2023 |
| Management Advisory Services Limited | Professional & scientific | 2025 |