| Minki Balinki Limited | Administrative & support | 2001 |
| Minsmere Green Apartments Management Company Limited | Households | 2025 |
| Minsmere Green Management Company Limited | Households | 2025 |
| Minstrel Ventures Limited | Administrative & support | 2016 |
| Mint FS Limited | Financial services | 2019 |
| Mintoncrest Limited | Real estate | 1990 |
| Minutiae Architectural Designs Ltd | Professional & scientific | 2026 |
| MIO Interiors Limited | Professional & scientific | 2011 |
| Mirasandkailah Ltd | Extraterritorial | 2021 |
| Mirfin Properties Ltd | Real estate | 2024 |
| Miris Finance Limited | Professional & scientific | 2018 |
| Miris Reporting Ltd | Professional & scientific | 2019 |
| Mirthquake Foundation | Other services | 2015 |
| Miss Tiff’S Limited | Other services | 2018 |
| Mission Analysis Limited | Professional & scientific | 2018 |
| Mission Partners Ltd | Professional & scientific | 2025 |
| Mission Submission Ltd | Arts & recreation | 2025 |
| Mitchams Park (Cambridge) Management Company Limited | Households | 2015 |
| Mitchell Curzon Events Ltd | Administrative & support | 2013 |
| Mitchell Motors Restoration Limited | Manufacturing | 2012 |
| Mitchen Green Ltd | Real estate | 2025 |
| Mithril Labs Ltd | Professional & scientific | 2026 |
| Mixed Signal Solutions Ltd | Information & communication | 2015 |
| MJ & SI Cleaning Services Ltd | Administrative & support | 2024 |
| MJ Husar Construction Ltd | Construction | 2020 |
| MJB GAS Solutions Ltd | Manufacturing | 2025 |
| MJF Cars Ltd | Wholesale & retail | 2022 |
| MJK Accountants Ltd | Professional & scientific | 2024 |
| MJW Commercial Services Limited | Professional & scientific | 2022 |
| MKB Installations Limited | Construction | 2022 |
| MKF Scaffolding Ltd | Construction | 2023 |
| MKM Building Limited | Construction | 2018 |
| MKT Property Developments Limited | Construction | 2025 |
| MLA & a Property Limited | Administrative & support | 2020 |
| MLT International Services Limited | Wholesale & retail | 2024 |
| MMB Projects Limited | Administrative & support | 2018 |
| Mmcf Trustee Limited | Extraterritorial | 2014 |
| Mmmr Academy Limited | Other services | 2025 |
| MNP Media Limited | Information & communication | 1999 |
| MO Garden Services Ltd | Administrative & support | 2023 |
| Moat House Consulting Limited | Information & communication | 2024 |
| Mobility Showers Ltd | Professional & scientific | 2025 |
| Moda Offices Limited | Real estate | 2018 |
| Modants Ltd | Wholesale & retail | 2019 |
| Modbox Ltd | Manufacturing | 2020 |
| Modular Fluid Systems Ltd | Manufacturing | 2022 |
| Moggleton Estates Limited | Real estate | 2020 |
| Mogsons Metals Limited | Water & waste | 2025 |
| Mogsonswaste Ltd | Water & waste | 2019 |
| Moleroda Finishing Systems Limited | Manufacturing | 1983 |
| Molloy Groundworks Ltd | Construction | 2008 |
| Mollys FAN Club Ltd | Administrative & support | 2025 |
| Momtara Limited | Wholesale & retail | 2026 |
| Monarch Scaffolds Ltd | Construction | 2025 |
| Moncreo Aveline Ltd | Real estate | 2022 |
| Moncreo Capital Limited | Financial services | 2020 |
| Moncreo Durnsford Ltd | Real estate | 2021 |
| Moncreo Holdings Limited | Financial services | 2020 |
| Monforte Wealth Limited | Professional & scientific | 2023 |
| Monkat Ltd | Professional & scientific | 2017 |
| Monkeyrun Limited | Professional & scientific | 2021 |
| Monro Higgs Consulting Limited | Real estate | 2008 |
| Montagu Place Management Limited | Households | 2021 |
| Montague Park (Buckhurst Farm) Management Company Limited | Households | 2015 |
| Montana Metals Ltd | Water & waste | 2023 |
| Montana Natural Slate Co Limited | Wholesale & retail | 1999 |
| Montario Solutions Ltd | Administrative & support | 2022 |
| Monte SAN Martino Trust | Education | 2005 |
| Monteacute Consulting Limited | Professional & scientific | 2024 |
| Montpelier Coach House Limited | Households | 2000 |
| Montpelier Pension Trustees Limited | Financial services | 2006 |
| Montrachet (Admaston) Management Company Limited | Households | 2011 |
| Monty Hugo Property Limited | Real estate | 2024 |
| Monument Mechanical Limited | Construction | 2019 |
| MOO Associates Ltd | Professional & scientific | 2026 |
| Moody Music Limited | Arts & recreation | 2004 |
| Moonfrost Ltd | Manufacturing | 2014 |
| Moore to Bookkeeping Ltd | Professional & scientific | 2023 |
| Moore-Wilson Commerce Systems Limited | Information & communication | 2003 |
| Moore-Wilson Limited | Information & communication | 2017 |
| Moore-Wilson New Media Ltd. | Information & communication | 1997 |
| Moores Build Limited | Construction | 2025 |
| Moorfield Mews Residents Management Company Limited | Households | 2024 |
| Moorhen Management Limited | Households | 2011 |
| Moot Electrical Limited | Professional & scientific | 2023 |
| Moot Systems Limited | Information & communication | 2017 |
| MOR Mechanical Ltd | Construction | 2018 |
| More Than Agency Limited | Professional & scientific | 2021 |
| Moreballmedia Limited | Information & communication | 2025 |
| Morecambe Moments Limited | Information & communication | 2000 |
| Moreton Road Management (Number 1) Limited | Households | 2009 |
| Morland Gardens (Abingdon) Management Company Limited | Households | 2015 |
| Morleigh Design Ltd | Construction | 2020 |
| Morning Star (Salisbury) | Hospitality | 2002 |
| Morrison and King Limited | Agriculture & fishing | 2006 |
| Morsleep Ltd | Hospitality | 2014 |
| Mortarculture Ltd | Administrative & support | 2025 |
| Morva Reach (Longrock) Management Company Limited | Households | 2023 |
| Mossymeadow Limited | Administrative & support | 2023 |
| Motivational Leadership Limited | Professional & scientific | 2008 |