| Macdonald & Sons Property Ltd | Real estate | 2026 |
| Machine Control Limited | Extraterritorial | 1971 |
| Machines for Beans Ltd | Wholesale & retail | 2022 |
| Mackay F Limited | Financial services | 2013 |
| Mackie AI Enterprises Limited | Information & communication | 2026 |
| Mackie Financial Holdings Limited | Financial services | 2021 |
| Maclennan Associates Ltd | Professional & scientific | 2008 |
| MAD Alice Ltd | Information & communication | 2020 |
| MAD Griffin Ltd | Construction | 2023 |
| MAD Press Ltd | Professional & scientific | 2023 |
| Maddox Ltd | Wholesale & retail | 2025 |
| Madeley Design and Build Ltd | Construction | 2022 |
| Mademoiselle Creative Studio Ltd | Professional & scientific | 2019 |
| MAE Investments Ltd | Real estate | 2025 |
| Magic Technology Ltd | Professional & scientific | 2023 |
| Magicae Verum Ltd | Wholesale & retail | 2020 |
| Magni Consulting Ltd | Information & communication | 2025 |
| Magnus Automotive Ltd | Wholesale & retail | 2025 |
| Mahato Tech Ltd | Wholesale & retail | 2015 |
| Maidenbower Sheetmetal Limited | Construction | 1997 |
| Mailtech Group International Limited | | 1984 |
| Main Street Studios Ltd | Information & communication | 1999 |
| Mainly Madness Limited | Arts & recreation | 2012 |
| Majestic Gifts Ltd | Wholesale & retail | 2003 |
| Majestico Ltd | Manufacturing | 2021 |
| Major Digital Ltd | Professional & scientific | 2007 |
| Major Mindgames Limited | Arts & recreation | 2021 |
| Make Space Self Storage Ltd | Professional & scientific | 1992 |
| Makeitaplan Limited | Administrative & support | 2014 |
| Makeology Ltd | Professional & scientific | 2026 |
| Malefidus Ltd | Real estate | 2024 |
| Mallards Estate Agents Limited | Real estate | 2006 |
| Malor Ltd | Wholesale & retail | 2025 |
| Malthouse Cottages Ltd | Real estate | 2021 |
| Malulu Ltd | Wholesale & retail | 2009 |
| MAN to MAN Skincare Limited | Wholesale & retail | 2017 |
| Management Educational Solutions Ltd | Education | 2012 |
| Mancave Barbers Ifield Ltd | Other services | 2023 |
| Manche Property UK Limited | Real estate | 2021 |
| Mancini Academy Limited | Education | 2025 |
| Mancini Legal Limited | Professional & scientific | 2011 |
| Mango Trees Limited | Professional & scientific | 2006 |
| Manic Munday Events Ltd | Hospitality | 2026 |
| Manitron Ltd | Transport & logistics | 2025 |
| Manor Fields NO. 3 Residents Company Limited | Households | 1986 |
| Manor Fields NO. 4 Residents Company Limited | Households | 1986 |
| Mansell Mctaggart Horsham Limited | Real estate | 2011 |
| Mansfield and Wood Ltd | Construction | 2019 |
| Mansfield Media Limited | Professional & scientific | 2025 |
| Mantell Global Logistics Ltd | Transport & logistics | 2024 |
| Mantis Sport International Limited | Administrative & support | 2010 |
| Mantra Magazines Ltd | Information & communication | 2006 |
| Manvell Ltd | Administrative & support | 2025 |
| Manzora Ltd | Wholesale & retail | 2001 |
| MAP Your Process Limited | Extraterritorial | 2020 |
| Maple Construction Limited | Construction | 2017 |
| Maple Leaf Lettings Ltd | Real estate | 2018 |
| Mapleday Limited | Education | 2021 |
| Maplehurst-Group Limited | Other services | 2020 |
| Maplepark Farms UK Ltd | Agriculture & fishing | 2025 |
| Marady’S Care Limited | Health & social care | 2019 |
| Marathon Communications Limited | Administrative & support | 2023 |
| Marble Entertainment Ltd | Arts & recreation | 2023 |
| Marc Tritschler Ltd | Arts & recreation | 2016 |
| Marcelo Delivery Services Ltd | Transport & logistics | 2019 |
| Marchant DRY Construction Ltd. | Construction | 2014 |
| Marchant Holdings Ltd | Financial services | 2025 |
| Marchant Properties Ltd | Real estate | 2019 |
| Marckus Limited | Information & communication | 2001 |
| Marco Trade Limited | Construction | 2014 |
| Mardam Property Investment Ltd | Real estate | 2019 |
| Marespand Finance Limited | Financial services | 2018 |
| Margaret Cottages Management Company Limited | Hospitality | 1999 |
| Margnor (Fasteners) Limited | Wholesale & retail | 1976 |
| Maria Phillips Project & Event Management Ltd | Professional & scientific | 2016 |
| Marie & Services Ltd | Health & social care | 2019 |
| Mario & Luigi Ltd Ltd | Other services | 2025 |
| Maritime Trade Associates Limited | Professional & scientific | 2025 |
| Mark Antony Limited | Manufacturing | 2009 |
| Mark Corliss Ltd | Information & communication | 2008 |
| Mark Durant Limited | Manufacturing | 2018 |
| Mark P Calvert Ltd | Financial services | 2023 |
| Marketing Edge Pharma Limited | Professional & scientific | 2006 |
| Marketing Musicians Ltd | Information & communication | 2019 |
| Marlborough Management (Grayshott) Ltd | Households | 2024 |
| Marlin Land and New Homes Limited | Construction | 2024 |
| Marlon Haus Ltd | Construction | 2024 |
| Marlow Sports Ltd | Arts & recreation | 2010 |
| Marotta Ltd | Wholesale & retail | 2024 |
| Marpat 4647 Ltd | Financial services | 2022 |
| Marsh Family Songs Ltd | Arts & recreation | 2021 |
| Marsh FPD Limited | Professional & scientific | 2021 |
| Marsham Estates Limited | Other services | 1964 |
| Martha's Blooming Gardens Ltd | Agriculture & fishing | 2023 |
| Martin & Steed Properties Limited | Real estate | 2025 |
| Martin Kirke Career Coaching Ltd | Professional & scientific | 2018 |
| Martlet Developments Ltd | Construction | 2019 |
| Marvel Limited | Real estate | 2019 |
| Marvelace Securities Limited | Administrative & support | 2025 |
| Masala Spice Horsham Ltd | Hospitality | 2025 |