| Maruti Crawley Ltd | Hospitality | 2023 |
| Maruti Developments Ltd | Construction | 2016 |
| Maruti East Grinstead Ltd | Hospitality | 2025 |
| Maruti Estates Leicester Limited | Real estate | 2014 |
| Maruti Global Ltd | Wholesale & retail | 2025 |
| Maruti Hastings Ltd | Hospitality | 2024 |
| Maruti Holdings Ltd | Wholesale & retail | 2023 |
| Maruti Littlehampton Ltd | Hospitality | 2024 |
| Maruti PH Group Ltd | Hospitality | 2023 |
| Maruti Worthing Ltd | Hospitality | 2024 |
| Marvel Education Ltd. | Education | 2017 |
| Marvel Primary Ltd | Education | 2019 |
| Marvel Sports Coaching Ltd | Education | 2019 |
| Marvellous Art Gallery Ltd | Wholesale & retail | 2019 |
| Marvi Care Ltd | Administrative & support | 2025 |
| Marvolo Renovations Limited | Construction | 2024 |
| Marwah Travels Limited | Administrative & support | 2016 |
| Marwar Caterers Ltd | Hospitality | 2020 |
| Marwo Ingredients Ltd | Wholesale & retail | 2014 |
| Marwood Absolute Ltd | Transport & logistics | 2015 |
| Marwood Convenience Store Limited | Wholesale & retail | 2009 |
| Mary & Grays Properties Ltd | Construction | 2025 |
| Mary's Properties Ltd | Real estate | 2022 |
| Marzh Holdings Limited | Real estate | 2018 |
| Marzh Investments Ltd | Real estate | 2015 |
| Marzh Properties Limited | Real estate | 2021 |
| MAS 1 Investments Ltd | Professional & scientific | 2018 |
| MAS Autos Ltd | Wholesale & retail | 2016 |
| MAS Elec and Property Services Ltd | Construction | 2026 |
| MAS Global Trading Ltd | Wholesale & retail | 2025 |
| MAS Management Ltd | Real estate | 2024 |
| MAS Press Knife & DIE Company Limited | Manufacturing | 1966 |
| MAS Prime Property Ltd | Real estate | 2026 |
| MAS Taxis Ltd | Transport & logistics | 2022 |
| MAS Theatre Company Ltd | Arts & recreation | 2025 |
| MAS Trading Cast Ltd | Wholesale & retail | 2017 |
| Masala Cottage PVT Ltd | Wholesale & retail | 2023 |
| Masala MIX Limited | Hospitality | 2024 |
| Masala MIX Oadby Limited | Hospitality | 2025 |
| Masalas Restaurants Limited | Hospitality | 2016 |
| Masark Limited | Financial services | 2017 |
| Masc (Leicester) Limited | Health & social care | 2020 |
| Mascot Vehicle Group Ltd | Transport & logistics | 2018 |
| Mash Auto's Ltd | Wholesale & retail | 2017 |
| Mashifa Electronics Ltd | Wholesale & retail | 2024 |
| Mashim Enterprise Limited | Wholesale & retail | 2025 |
| Mashwerx Ltd | Information & communication | 2024 |
| Masik Ltd | Other services | 2015 |
| Mask Commerce Ltd | Wholesale & retail | 2026 |
| Mask Developments UK Ltd | Wholesale & retail | 2024 |
| Masked Detailing Ltd | Wholesale & retail | 2022 |
| Maslink Strategic Procurement Limited | Extraterritorial | 2012 |
| Mason & King Limited | Manufacturing | 1954 |
| Mason Foodservice Limited | Wholesale & retail | 1965 |
| Mason Jointing Solutions Limited | Construction | 2017 |
| Mason Lewis Bricklaying and Property Development Ltd | Construction | 2017 |
| Mason Properties & Lettings Limited | Construction | 2024 |
| Mason ROW Ltd | Financial services | 2014 |
| Mason Smalley Ltd | Financial services | 2020 |
| Mass Technology (UK) Ltd | Wholesale & retail | 2005 |
| Massey Construction Developments Limited | Construction | 2025 |
| Massey Truck Engineering Limited | Manufacturing | 1991 |
| Masspetals Limited | Health & social care | 2014 |
| Masswa Ltd | Administrative & support | 2017 |
| Mast Property Services Ltd | Real estate | 2009 |
| Mastan Holdings Limited | Financial services | 2018 |
| Master Auto Services Ltd | Wholesale & retail | 2025 |
| Master Cabs Leicester Ltd | Transport & logistics | 2020 |
| Master Commercial Ltd | Construction | 2023 |
| Master Developments Group Limited | Construction | 2018 |
| Master Family Investments Ltd | Financial services | 2024 |
| Master Food London Ltd | Hospitality | 2024 |
| Master Kebab & Doner Ltd | Administrative & support | 2017 |
| Master Kebab Ltd | Hospitality | 2026 |
| Master Marketing Ltd | Administrative & support | 2015 |
| Master New Trade Ltd | Transport & logistics | 2015 |
| Master Scaff Ltd | Construction | 2018 |
| Master Your Life (UN) Limited | Professional & scientific | 2023 |
| Master's Dream Properties Ltd | Real estate | 2024 |
| Masterair Limited | Energy | 2007 |
| Mastercraft Plumbing, Heating and Cooling Ltd | Construction | 2025 |
| Masterfit Solutions Limited | Construction | 2025 |
| Mastermind Analytics Limited | Information & communication | 2019 |
| Mastermind Ecommerce UK Limited | Wholesale & retail | 2019 |
| Mastermind Tuition Limited | Education | 2021 |
| Masterplan Design Ltd | Professional & scientific | 2011 |
| Masters Hand Wash Limited | Administrative & support | 2025 |
| Masters of PIE Limited | Information & communication | 2011 |
| MASTERSAERO(2024) Limited | Transport & logistics | 2024 |
| Masterson Trading Ltd | Other services | 2020 |
| Masty Design Ltd | Manufacturing | 2024 |
| Masuku Limited | Wholesale & retail | 2014 |
| Masy & Co Property Ltd | Real estate | 2025 |
| Masyana Enterprises Ltd | Real estate | 2022 |
| Masz Technologies Limited | Information & communication | 2016 |
| MAT Williams Limited | Real estate | 2026 |
| Mat-Tastic UK Limited | Manufacturing | 2019 |
| Matador Products Ltd | Wholesale & retail | 2021 |
| Matbros Ltd | Real estate | 2006 |
| Match Empire Limited | Information & communication | 2025 |