| Mensa Vera Ltd | Manufacturing | 2026 |
| Mentorly Ltd | Professional & scientific | 2024 |
| MERA25 Limited | Manufacturing | 2026 |
| Merak Housing C.I.C. | Real estate | 2023 |
| Mercurier Wholesale Limited | Wholesale & retail | 2026 |
| Mercury Corporate Services Limited | Professional & scientific | 2019 |
| Mercury Dreams Ltd | Wholesale & retail | 2022 |
| MERGE2OWN UK Ltd | Real estate | 2025 |
| Merlin Flying Cameras Ltd | Professional & scientific | 2014 |
| Merlin Media Limited | Information & communication | 2023 |
| Merlin Park (Mildenhall) M.C. Limited | Real estate | 1989 |
| Merseyside Property Management Limited | Households | 2010 |
| Mertivaa Ltd | Wholesale & retail | 2025 |
| Merve Bulut Ltd | Wholesale & retail | 2021 |
| Mervisth Trade Ltd | Wholesale & retail | 2026 |
| Mesh Waste Services Limited | Water & waste | 2024 |
| Message Mugz Ltd | Wholesale & retail | 2026 |
| Meta Edge 2 Ltd | Information & communication | 2026 |
| Meta Edge Group Ltd | Information & communication | 2025 |
| Meta Gold Group Ltd | Information & communication | 2025 |
| Meta Premier Group Ltd | Information & communication | 2025 |
| META25GROUP Ltd | Information & communication | 2025 |
| META26 Group Ltd | Information & communication | 2025 |
| Metabolix Ltd | Other services | 2023 |
| Metal Export Import LLP | | 2014 |
| Metaphase Ltd | Wholesale & retail | 2022 |
| Metavance Limited | Wholesale & retail | 2025 |
| Metcalfe Films Ltd | Information & communication | 2023 |
| Metlux Sales (I) LLP | | 2018 |
| Metric Menus Ltd | Hospitality | 2025 |
| Metropolis Living Ltd | Real estate | 2025 |
| Mettle Works Community Ltd | Arts & recreation | 2019 |
| MF Digital Solutions Ltd | Information & communication | 2024 |
| Mfgf Limited | Wholesale & retail | 2024 |
| MFO Properties and Investments Limited | Real estate | 1987 |
| Mfuels Ltd | Wholesale & retail | 2023 |
| MGH Entertainment Limited | Extraterritorial | 2020 |
| MH Property Ventures Ltd | Real estate | 2023 |
| Miah Sapphire Ltd | Wholesale & retail | 2025 |
| Miahtech Ltd | Information & communication | 2023 |
| Miami Boat Place LLP | | 2025 |
| Mibest Project Controls Ltd | Professional & scientific | 2024 |
| Mibolartix Limited | Wholesale & retail | 2026 |
| Michael Cerny Limited | Financial services | 2018 |
| Michaela Enterprises Ltd | Wholesale & retail | 2022 |
| Micro COM Support Limited | Information & communication | 2016 |
| MID Anglia First AID & Fire Services Limited | Health & social care | 2000 |
| Middie Accountancy Limited | Professional & scientific | 2014 |
| Middleage Handicrafts Ltd | Wholesale & retail | 2026 |
| Midland BIO UK Limited | Professional & scientific | 2026 |
| Midlands Social Lets Limited | Real estate | 2024 |
| Midm Engineering Limited | Construction | 2024 |
| Midnightblades Ltd | Wholesale & retail | 2026 |
| Mido X Trade Limited | Wholesale & retail | 2025 |
| Midosi (GMT) Limited | Administrative & support | 2005 |
| Mikvar Ltd | Wholesale & retail | 2023 |
| Milanco Ltd | Wholesale & retail | 2025 |
| Milasius Investments Limited | Financial services | 2024 |
| Milasius Land Limited | Construction | 2025 |
| Mildenhall Moto-Cross Limited | Arts & recreation | 2014 |
| Mile 26 Consulting Ltd | Information & communication | 2025 |
| Miles & Co Group Ltd | Professional & scientific | 2025 |
| Milestone Motorsport Ltd | Extraterritorial | 2022 |
| Military Car Sales Germany Ltd | Information & communication | 2024 |
| Miller Hudson Property Solutions Ltd | Real estate | 2023 |
| Millerhudson Holdings Ltd | Financial services | 2024 |
| Millerhudson Management Ltd | Real estate | 2024 |
| Millfield Tech Ltd | Wholesale & retail | 2026 |
| Millvera Property Services Limited | Administrative & support | 2025 |
| Miloza Limited | Information & communication | 2025 |
| Mimi and LU Ltd | Professional & scientific | 2025 |
| Mina Bazaar Ltd | Wholesale & retail | 2024 |
| Minbel Holdings Ltd | Financial services | 2026 |
| Mind Mage Ltd | Information & communication | 2024 |
| Mind of Makus Limited | Education | 2023 |
| Mindfairground Ltd | Information & communication | 2025 |
| Mindfirst Counselling Ltd | Health & social care | 2025 |
| Mindfool Limited | Wholesale & retail | 2022 |
| Mindful Cloud Games Ltd | Information & communication | 2025 |
| Mindgem Trading Limited | Wholesale & retail | 2025 |
| Mindivo Limited | Information & communication | 2025 |
| Minds in Motion Ltd | Extraterritorial | 2023 |
| Mindscape Studio CIC | Education | 2025 |
| Mindsia Mental Health and Wellbeing Group CIC | Health & social care | 2024 |
| Mindspace Digital Limited | Wholesale & retail | 2025 |
| Minikittens Ltd | Wholesale & retail | 2025 |
| Minnies Hair Academy Ltd | Education | 2025 |
| Minqu Easy Ltd | Wholesale & retail | 2026 |
| Mintfork Ltd | Professional & scientific | 2025 |
| Mintsugar Ltd | Wholesale & retail | 2026 |
| Miola Property Group Ltd | Real estate | 2023 |
| Mirenox Co., Ltd | Wholesale & retail | 2026 |
| Mirex Ventures Limited | Wholesale & retail | 2025 |
| Mirola Ltd | Professional & scientific | 2017 |
| Misaani Ltd | Wholesale & retail | 2024 |
| Misana Ltd | Wholesale & retail | 2026 |
| Mischievous Films Ltd | Information & communication | 2018 |
| Mission to Change Ltd | Professional & scientific | 2024 |
| Mistry Design & Build Ltd | Construction | 2019 |
| Misty Beauty Vending Ltd | Wholesale & retail | 2025 |