| Maitre Parfumeur Ltd | Wholesale & retail | 2024 |
| Majaru Decorating Ltd | Construction | 2019 |
| Majic Breaks Ltd | Hospitality | 2025 |
| Majimoto Ltd | Wholesale & retail | 2006 |
| Makepeace Klassen 221 Limited | Financial services | 2024 |
| Makepeace Klassen Ltd | Financial services | 2022 |
| Makeup London Academy Limited | Other services | 2013 |
| Making People Great Ltd | Information & communication | 2023 |
| Mallett Property Developments Limited | Construction | 2018 |
| Maloja Limited | Financial services | 2023 |
| Maltbys Limited | Construction | 1973 |
| Maltings Management Company (Canterbury) Limited(The) | Households | 1984 |
| Mammoth Homes Ltd | Real estate | 2019 |
| Mana Venture Enterprise Limited | Financial services | 2022 |
| Manderley Communications Ltd | Administrative & support | 2017 |
| Mango Swiss Limited | Information & communication | 2008 |
| Mania Escape Rooms Ltd | Arts & recreation | 2023 |
| Mannequin Magazine Ltd | Information & communication | 2017 |
| Mannings Decorators Limited | Construction | 2025 |
| Mannock Drive Management Company Limited | Households | 2020 |
| Manor Fields Property Ltd | Real estate | 2022 |
| Manor Grove (Botswana) Limited | Extraterritorial | 2010 |
| Manor Grove Property LLP | | 2021 |
| Manor Heating Ltd | Construction | 2015 |
| Manor Road Management Limited | Hospitality | 2004 |
| Manor Wines Limited | Hospitality | 2004 |
| Manse Designs Ltd | Professional & scientific | 2019 |
| Manse Developments Ltd | Construction | 2023 |
| Mansell Investment Group Ltd | Financial services | 2024 |
| Mansfield Court (One) RTM Company Limited | Households | 2019 |
| Mansfield Court (Two) RTM Company Limited | Households | 2019 |
| Mansfield Farms Group Limited | Professional & scientific | 2004 |
| Mansfield Farms Limited | Real estate | 2004 |
| Mansfield Fruit Farms Limited | Wholesale & retail | 2012 |
| Mansfield Greosn Limited | Agriculture & fishing | 2017 |
| Mansion Events Ltd | Hospitality | 2020 |
| Mansion Works Ltd. | Real estate | 2019 |
| Maplejak Investment Ltd | Real estate | 2010 |
| Maplewood Properties Ltd | Real estate | 2025 |
| Marbella Limited | Other services | 2022 |
| Marble Hall Properties Limited | Real estate | 2021 |
| Marble Vineyard Ltd | Agriculture & fishing | 2023 |
| Marc FRY Consulting Ltd | Professional & scientific | 2021 |
| Marcoz Properties and Developments Limited | Real estate | 1985 |
| Marcus Benton Limited | Professional & scientific | 2015 |
| Marcus Mays Productions Limited | Other services | 2013 |
| Marden Court Bexhill Limited | Households | 1989 |
| Maresalu Trans Ltd | Transport & logistics | 2026 |
| Margaret Connolly Tax and Business Consulting Limited | Professional & scientific | 2015 |
| Maria Gluzdakova CGI Ltd | Professional & scientific | 2025 |
| Marico Constructions Ltd | Construction | 2019 |
| Marico Renovations Ltd | Real estate | 2016 |
| Marilyn Court Management Company (Westgate-On-Sea) Limited | Real estate | 1989 |
| Marine Wharfs Limited | Real estate | 2017 |
| Marino's Fish Bars Limited | Hospitality | 2007 |
| Maritime Travel Limited | Administrative & support | 2017 |
| Mariusz Daniel Owczarzak Limited | Professional & scientific | 2024 |
| Mark Cosgrave Wealth Management Limited | Financial services | 2019 |
| Mark Developments Limited | Real estate | 1985 |
| Mark Heller Property Investments Limited | Real estate | 2019 |
| Mark Russell Glazing Limited | Construction | 1993 |
| Market Square Residents Management Company Limited | Households | 2014 |
| Marketing Essentials LAB Limited | Professional & scientific | 2020 |
| Markminster (1989) Limited | Construction | 1989 |
| Marley Fields Management Company Limited | Households | 2021 |
| Marleybrook House Ltd | Administrative & support | 2013 |
| Marlowe Avenue Management Company Limited | Households | 1994 |
| Marlowe Consulting Limited | Professional & scientific | 2014 |
| Marlowe Consulting Services Ltd | Financial services | 2023 |
| Marlowe Group Limited | Financial services | 2022 |
| Marlowe Language CIC | Information & communication | 2024 |
| Marlowe Theatre Productions Limited | Arts & recreation | 2025 |
| Marsden Maintenance Ltd | Construction | 2025 |
| Marshside Holdings Ltd | Wholesale & retail | 2019 |
| Martesta Limited | Real estate | 2017 |
| Martin Gorse Wood Clay Pigeon Club Limited | Arts & recreation | 2007 |
| Martin Yates Experience Design Ltd | Information & communication | 2017 |
| Marvellous Minds Creatives Limited | Information & communication | 2022 |
| Marvellous Minds Ltd | Education | 2013 |
| Marzo Studio Ltd. | Information & communication | 2020 |
| Mashar Ltd | Wholesale & retail | 2025 |
| Mason Estates South East Limited | Real estate | 2022 |
| Mason MEP Ltd | Construction | 2025 |
| Mass Properties and Homes Limited | Hospitality | 2025 |
| Master Tech One Limited | Wholesale & retail | 2022 |
| Matches Sports Bar and Grill (Ashford) Ltd | Hospitality | 2019 |
| Matches Sports Bar and Grill (Canterbury) Limited | Hospitality | 2022 |
| Matches Sports Bar and Grill Holdings Ltd | Hospitality | 2022 |
| Math Family Limited | Hospitality | 2024 |
| Mathers&Company Ltd | Professional & scientific | 2024 |
| Matrix Consultancy Ltd | Information & communication | 2009 |
| Matrix Receivables Limited | Professional & scientific | 2020 |
| Matt Fiddes Martial Arts Essex LLP | | 2021 |
| Matt Ziomek Ltd | Construction | 2025 |
| Matt. Inc Group Limited | Financial services | 2023 |
| Maude Francis Ltd | Professional & scientific | 2026 |
| MAX Auto Colour Ltd | Wholesale & retail | 2021 |
| MAX Development Solutions Ltd | Information & communication | 2020 |
| MAX Plan 1 Ltd | Other services | 2014 |
| MAX Plan 3 Limited | Other services | 2016 |