| Mike & Riko's Spuds Ltd | Hospitality | 2025 |
| Mike 'A'Part Limited | | 1991 |
| Mike Curtis Construction Ltd | Construction | 2017 |
| Mike England Plastering South Ltd | Construction | 2017 |
| Mike Gems & Crystal Factory Ltd | Wholesale & retail | 2026 |
| Mike Grant Consulting Ltd | Professional & scientific | 2018 |
| Mike Hurst Zine Ltd | Information & communication | 2011 |
| Mike RAY Limited | Other services | 2022 |
| Mike ROA Financial Services Limited | Financial services | 2012 |
| Mike Samuels Copywriting Ltd | Other services | 2015 |
| Mike Sharman Ltd | Professional & scientific | 2013 |
| Mike Tyler Limited | Information & communication | 2014 |
| Mikes Plumbing & Heating Ltd | Construction | 2009 |
| Mikrotik Training and Consulting Ltd | Information & communication | 2023 |
| MIL Technical GAS Services Limited | Professional & scientific | 2016 |
| MIL Trans Limited | Transport & logistics | 2018 |
| Milad & Aaron Limited | Construction | 2023 |
| Milagros Management Limited | Other services | 2018 |
| Milamya 42 Limited | Other services | 2017 |
| Milan Hairstyles Ltd | Other services | 2023 |
| Milan Prime Logistics Ltd | Transport & logistics | 2026 |
| Milburn Engineering & Steelwork Services Ltd | Manufacturing | 2016 |
| Mildenhall RTE Limited | Households | 2006 |
| Miles Logistics UK Ltd | Wholesale & retail | 2025 |
| Miles of Value Limited | Wholesale & retail | 2012 |
| Miles Russell Limited | Real estate | 2021 |
| Milestone Property LLP | | 2012 |
| Milestone Support Services Limited | Health & social care | 2017 |
| Milestones Nursery Ltd | Education | 2024 |
| Milford Flats Management Company Limited | Households | 1974 |
| Milford on Sea Park Limited | Hospitality | 2017 |
| Milguard Security Limited | Administrative & support | 2024 |
| Milieu Consult Limited | Professional & scientific | 2009 |
| Milieu Consulting Engineers Limited | Professional & scientific | 2012 |
| Military Direct Limited | Financial services | 2006 |
| Military Precision Pest Control Ltd | Administrative & support | 2019 |
| Milk and GIN Ltd | Information & communication | 2021 |
| Milko Electrics Ltd | Energy | 2026 |
| Mill Developments Limited | Construction | 1992 |
| Millbank Auctioneers Limited | Other services | 2008 |
| Millbank Consultants Limited | Wholesale & retail | 2024 |
| Millbank Property Estates Ltd | Real estate | 2007 |
| Millbank Recovery Limited | Other services | 2009 |
| Millbrook Auto Bodyworks Ltd | Wholesale & retail | 2025 |
| Millbrook Carpets and Flooring Limited | Wholesale & retail | 2026 |
| Millbrook Furnishing Industries Ltd | Extraterritorial | 1998 |
| Millbrook Group Ltd | Manufacturing | 1983 |
| Millbrook Healthcare Bidco Ltd | Financial services | 2019 |
| Millbrook Healthcare Group II Limited | Professional & scientific | 2019 |
| Millbrook Healthcare Group Limited | Professional & scientific | 1998 |
| Millbrook Healthcare Holdings Limited | Financial services | 2019 |
| Millbrook Healthcare Ltd | Health & social care | 1965 |
| Millbrook Healthcare Midco Limited | Financial services | 2019 |
| Millbrook Healthcare One Limited | Professional & scientific | 1995 |
| Millbrook Healthcare Subco Limited | Financial services | 2019 |
| Millbrook Healthcare Two Limited | Financial services | 2020 |
| Millbrook Industries Limited | Real estate | 2019 |
| Millbrook Manufacturing Industries Ltd | Extraterritorial | 2008 |
| Millennium Design Ltd. | Information & communication | 1990 |
| Millie's Tea Room Ltd | Hospitality | 2018 |
| Millkae Limited | Health & social care | 2023 |
| Millrose Ltd | Real estate | 2026 |
| Millscapes Ltd | Administrative & support | 2022 |
| Millys PAW Care Ltd | Agriculture & fishing | 2025 |
| Milman Court Management Company Limited | Households | 1997 |
| Milne (Land & Planning) Limited | Administrative & support | 2024 |
| Milonas Limited | Transport & logistics | 2018 |
| Milton Keynes Removals and Storage Limited | Professional & scientific | 2003 |
| Milton Ransom Limited | Extraterritorial | 2010 |
| Milton Speyside Limited | Information & communication | 2021 |
| Miluna Limited | Hospitality | 2024 |
| Milunia Limited | Wholesale & retail | 2023 |
| Mimident Ltd | Health & social care | 2012 |
| Mimiyou Ltd | Wholesale & retail | 2018 |
| Mimo Connect Ltd | Information & communication | 2018 |
| Mimosa Properties Ltd | Real estate | 2017 |
| Mimt Limited | Professional & scientific | 2012 |
| Mind Bubble Learning Ltd | Professional & scientific | 2016 |
| Mind Companion Limited | Education | 2025 |
| Mind Monkey AI Ltd | Professional & scientific | 2024 |
| Mind Your Own Content Limited | Information & communication | 2004 |
| Mindfit Community Ltd | Other services | 2025 |
| Mindmill Limited | Information & communication | 2007 |
| Mindset Personal Training Academy Ltd | Education | 2020 |
| Minerva Procurement Consultancy Services Limited | Administrative & support | 2010 |
| Ming’S Dynasty Limited | Hospitality | 2020 |
| Mini Amsterdam Hampshire Ltd | Wholesale & retail | 2023 |
| Minicabees Ltd | Transport & logistics | 2024 |
| Minimal Access Research & Training (Mart) Ltd | Health & social care | 2018 |
| Ministry of Medics Ltd | Health & social care | 2024 |
| Minitek Fabrications Limited | Wholesale & retail | 2018 |
| Minitopia Ltd | Wholesale & retail | 2016 |
| Minjoy Trading Taizhou Co Ltd | Wholesale & retail | 2025 |
| Minnie and Pickle PUB Co Ltd | Hospitality | 2026 |
| Minoa Accessories Ltd | Manufacturing | 2025 |
| Minstead Court and Wessex Court (Westwood Road Southampton) Management Co. Limited | Households | 1989 |
| Minstead Court Management Limited | Households | 1994 |
| Mint Dosa Limited | Hospitality | 2016 |
| Mint Hair Designs Ltd | Other services | 2016 |
| Mipac Limited | Health & social care | 2019 |