| Millview Meadows (Ringmer) Management Company Ltd | Households | 2024 |
| Millwood Servicing Limited | Other services | 1993 |
| Millwork Plus Limited | Manufacturing | 2025 |
| Milly Entertainment Limited | Information & communication | 2026 |
| Milnes Bros Limited | Manufacturing | 2022 |
| Milnthorpe Court Freehold Limited | Households | 2014 |
| Milton Lodge (Twickenham) Limited | Households | 2004 |
| Miluxe Care Services Ltd | Health & social care | 2025 |
| Mimco Media Ltd | Administrative & support | 2023 |
| Mimi-Viv Consultancy Limited | Health & social care | 2009 |
| Mimine AG Ltd | Professional & scientific | 2018 |
| Mimo ADE Ltd | Health & social care | 2015 |
| Minaa Holding Ltd | Real estate | 2024 |
| Minacia Ltd | Wholesale & retail | 2023 |
| Minaphil Ltd | Wholesale & retail | 2023 |
| Minar's Capital Ltd | Real estate | 2023 |
| Mind the Power Ltd | Professional & scientific | 2025 |
| Mind Work Matters Limited | Education | 2020 |
| Mindful Brains Ltd | Other services | 2025 |
| Mindful Contract Solutions Limited | Professional & scientific | 2013 |
| Mindful Investments Holding Limited | Financial services | 2019 |
| Mindful Nurseries Ltd | Health & social care | 2020 |
| Mindgold Limited | Real estate | 2003 |
| Minds Over Matters Ltd | Health & social care | 2012 |
| Mindsight Sport Ltd | Information & communication | 2023 |
| Mindstep Consulting Limited | Professional & scientific | 2025 |
| Mindtrance Ltd | Health & social care | 2025 |
| Mineco International Limited | Wholesale & retail | 2014 |
| Mineco Limited | Professional & scientific | 2005 |
| Minecuta Cleaning Services Ltd | Administrative & support | 2025 |
| Mini Munchkins Preschool and Childcare Services Limited | Education | 2019 |
| Mini Treasures Day Nursery Croydon Limited | Education | 2025 |
| Minidots Ltd | Information & communication | 2025 |
| Miniseat Ltd | Information & communication | 2026 |
| Minority Beauty Ltd | Wholesale & retail | 2016 |
| Minpro 2009 Limited | Manufacturing | 2009 |
| Mint and Curry Leaves Ltd | Hospitality | 2018 |
| Mint Network Limited | Information & communication | 2006 |
| Minters London Ltd | Construction | 2017 |
| Minton Court RTM Company Ltd | Households | 2021 |
| Minuara Limited | Financial services | 2022 |
| Minutes Forward Ltd | Information & communication | 2021 |
| Minutsa Limited | Information & communication | 2024 |
| Minxx Club Ltd | Wholesale & retail | 2024 |
| Mira and Ltd | Wholesale & retail | 2026 |
| Mirabelle (Roman Meadow) Management Company Limited | Households | 2021 |
| Mirabelle Communications Limited | Professional & scientific | 1991 |
| Miracle Gardening and Landscaping Ltd | Administrative & support | 2022 |
| Miranex Consulting Ltd | Financial services | 2025 |
| Mirela 74 Ltd | Construction | 2015 |
| Mirkor Ltd | Hospitality | 2025 |
| Mirror Over Thames Ltd | Arts & recreation | 2022 |
| Mirza & Sons Properties Ltd | Real estate | 2024 |
| Misa Holdings Limited | Financial services | 2022 |
| Mismatch Ltd | Information & communication | 2024 |
| Misorana & Co Ltd | Professional & scientific | 2024 |
| Miss Black & Beautiful UK Ltd | Arts & recreation | 2025 |
| Miss Brazil Ltd | Wholesale & retail | 2022 |
| Miss Krupa Madhvani Limited | Health & social care | 2022 |
| Miss Lasagna Ltd | Hospitality | 2020 |
| Miss Lulu Creates Ltd | Arts & recreation | 2020 |
| Miss Socialite Ltd | Information & communication | 2025 |
| Mission for Christ Pentecostal Ministry CIC | Education | 2022 |
| Mistablend Ltd | Manufacturing | 2021 |
| Mister Fixer (Croydon) Ltd | Construction | 2026 |
| Mister Meat Halal Butchers Ltd | Wholesale & retail | 2026 |
| Mister Supplies Ltd | Wholesale & retail | 2026 |
| Mistley Thorn Residents Association RTM Company Limited | Households | 2004 |
| Mitcap Partners Ltd | Professional & scientific | 2011 |
| Mitcham Belle Coaches Limited | Transport & logistics | 2005 |
| Mitcham Driving School Ltd | Education | 2023 |
| Mitcham Garden Village | Hospitality | 1930 |
| Mitchell Cotts Ethiopia Limited | Extraterritorial | 1960 |
| Mitchell House Freehold Limited | Households | 2007 |
| Mitchell's Place Management Company Limited | Real estate | 1999 |
| Mithai Wala Limited | Hospitality | 2015 |
| Mithia Properties Limited | Construction | 2009 |
| Mito Construction & Engineering Limited | Wholesale & retail | 1975 |
| Mixed Heritage Press Ltd | Information & communication | 2024 |
| Mixing Masters Ltd | Arts & recreation | 2023 |
| Mizbe’Ach Elohim Ltd | Wholesale & retail | 2025 |
| Miziyasoft Ltd | Information & communication | 2018 |
| Mizu Management Limited | Real estate | 2025 |
| MJ Contractors Ltd | Construction | 2026 |
| MJ Enterprises Ltd | Wholesale & retail | 2026 |
| MJ Expertise Ltd | Wholesale & retail | 2025 |
| MJ Steady Movers Limited | Transport & logistics | 2018 |
| MJB Actuarial Services Ltd | Financial services | 2018 |
| MJB Facilities Management Ltd | Administrative & support | 2018 |
| MJB Holding Group Ltd | Administrative & support | 2026 |
| MJC Clothing Limited | Wholesale & retail | 2024 |
| MJG Electrical Ltd | Construction | 2021 |
| MJG Property Investments Ltd | Real estate | 2020 |
| MJK Trans Ltd | Transport & logistics | 2017 |
| MJL Properties Limited | Real estate | 2002 |
| MJM House Maintenance Ltd | Construction | 2021 |
| MJR Family Ltd | Hospitality | 2023 |
| MJS Rail Ltd | Construction | 2009 |
| Mjsj Property Holdings Limited | Real estate | 2024 |
| MJV Extrem Construction Ltd | Construction | 2013 |