| Milby Grange Residents Management Company Limited | Households | 2019 |
| Mile View Court Limited | Real estate | 2023 |
| Mileaf Ltd | Hospitality | 2016 |
| Milenkom Services Limited | Information & communication | 2025 |
| Miles & Cash Limited | Extraterritorial | 2012 |
| Miles Hilton-Barber Limited | Professional & scientific | 2004 |
| Miles Resourcing Limited | Administrative & support | 2017 |
| Milesight UK Limited | Extraterritorial | 2019 |
| Milestone Construction (Midlands) Limited | Construction | 2003 |
| Milestone Finishes Ltd | Construction | 2026 |
| Milestone Transport Ltd | Transport & logistics | 2026 |
| Milford Developments (Derby) Ltd | Construction | 2024 |
| Milford Taverns Limited | Real estate | 2014 |
| Milia MAC Care Limited | Health & social care | 2023 |
| Mill Chase Park Residents Management Company Limited | Households | 2024 |
| Mill Green Community Management Limited | Households | 2017 |
| Mill Green Developments Limited | Construction | 2016 |
| Mill Homes (Derby) Ltd | Real estate | 2018 |
| Mill House Development & Investment Group Ltd | Construction | 2007 |
| Mill Lane Corner Limited | Real estate | 2020 |
| Mill Oak Properties Ltd | Real estate | 2023 |
| Mill View JV LLP | | 2023 |
| Mill Wheel (Hartshorne) Limited | Hospitality | 2015 |
| Millar Aviation Ltd | Transport & logistics | 2026 |
| Millar Management Holdings Limited | Financial services | 2023 |
| Millar Management Limited | Professional & scientific | 2001 |
| Millbrook Medical Conferences Limited | Administrative & support | 1995 |
| Millbrook Medical Logistics Limited | Administrative & support | 2018 |
| Millbrook Technology Solutions Limited | Information & communication | 2002 |
| Millbrooke Homes Limited | Construction | 2023 |
| Millenium Properties Limited | Real estate | 2018 |
| Millenium Site Services (UK) Limited | Manufacturing | 2000 |
| Millennium Property UK Limited | Real estate | 1996 |
| Millennium UK Homes Limited | Real estate | 2025 |
| Miller (Cobblers Hall) Limited | Construction | 2005 |
| Miller (Eccles) Limited | Construction | 2005 |
| Miller (Houghton Conquest) Limited | Real estate | 2023 |
| Miller @ Stoke Golding Management Company Limited | Households | 2023 |
| Miller Airdrie Limited | Construction | 1986 |
| Miller and Jackson Limited | Wholesale & retail | 2011 |
| Miller Fairclough Management Services Limited | Construction | 2002 |
| Miller Fairclough UK Limited | Construction | 1999 |
| Miller Framwellgate Limited | Construction | 2007 |
| Miller Gadsby (Heatherton) Limited | Construction | 2009 |
| Miller Homes Cambridge Limited | Construction | 1998 |
| Miller Homes Group (Finco) PLC | Financial services | 2022 |
| Miller Homes Group Holdings Limited | Financial services | 2017 |
| Miller Homes Group Limited | Financial services | 2017 |
| Miller Homes Streethay Limited | Construction | 2025 |
| Miller Maidenhead Limited | Construction | 2006 |
| Miller Midco 1 Limited | Financial services | 2017 |
| Miller Midco 2 Limited | Financial services | 2017 |
| Miller Property Holdings Ltd | Real estate | 2025 |
| Miller Property Management Services Limited | Real estate | 2024 |
| Miller Residential (Northern) Limited | Construction | 2000 |
| Miller Wates (Bracklesham) Limited | Construction | 2016 |
| Miller Wates (Chalgrove) Limited | Construction | 2018 |
| Miller Wates (Didcot) Limited | Construction | 2015 |
| Miller Wates (Oakley) LLP | | 2022 |
| Miller Wates (Southwater) Limited | Construction | 2015 |
| Miller Wates (Wallingford) Limited | Construction | 2016 |
| Millgate Property Management Co. Limited | Hospitality | 2002 |
| Millhouse (Derby) Management Company Limited | Real estate | 2004 |
| Millhouse (Gerrards Cross) Limited | Construction | 2025 |
| Millhouse (Hanley) Limited | Construction | 2023 |
| Millhouse (Liverpool) Ltd | Professional & scientific | 2002 |
| Millhouse Care Developments Ltd | Construction | 2007 |
| Millhouse Magna Carta Lincoln Limited | Construction | 2024 |
| Millhouse Securities Limited | Real estate | 2013 |
| Millington Technologies Limited | Information & communication | 2025 |
| Millino Ltd | Real estate | 2023 |
| Millitec Export Limited | Manufacturing | 2024 |
| Millitec Food Systems Ltd | Manufacturing | 2005 |
| Millitec Group Limited | Financial services | 2024 |
| Millitec UK Limited | Manufacturing | 2024 |
| Millmai Ltd | Construction | 2018 |
| Millrose (Lammack Road) Estate Management Company Limited | Households | 2020 |
| Mills Wheatley Ltd | Real estate | 2022 |
| Millstone Joinery & Building Ltd | Construction | 2024 |
| Millward Bros.(Motor Engineers)Limited | Real estate | 1961 |
| Milmac (Dutch Spotted Sheep) Ltd | Agriculture & fishing | 2024 |
| Milner Commercial Property Limited | Administrative & support | 1997 |
| Milspec Ltd | Health & social care | 2023 |
| Milton Electricals Ltd | Manufacturing | 2022 |
| Milward-Brown & Associates Limited | Professional & scientific | 2006 |
| Milwarner Consulting Limited | Professional & scientific | 2023 |
| MIM Holdings Limited | Health & social care | 2020 |
| Mimi Toko Duffield Ltd | Wholesale & retail | 2010 |
| MIN Investor Limited | Real estate | 2024 |
| Minani Solar Ltd | Construction | 2025 |
| Minc Estate Ltd | Real estate | 2016 |
| Mind Psych Ltd | Health & social care | 2024 |
| Mind&Body Health Coaching Ltd | Wholesale & retail | 2020 |
| Mindfit Coaching Limited | Other services | 2013 |
| Mindfuelness Ltd | Health & social care | 2023 |
| Mindful Advisory Ltd | Professional & scientific | 2023 |
| Mindful Living Ventures Ltd | Financial services | 2022 |
| Mindful Properties Ltd | Real estate | 2021 |
| Mindfulness Consult Limited | Administrative & support | 2024 |
| Mindfulness Health Consulting Ltd | Health & social care | 2020 |