| Lucky Brands Ltd | Manufacturing | 2020 |
| Lucky Loopy Limited | Hospitality | 2019 |
| Lukey Power Generation Limited | Construction | 2017 |
| Luna Home Improvements Ltd | Construction | 2020 |
| Luna Lettings (SW) Limited | Hospitality | 2021 |
| Luna's Locket Ltd | Manufacturing | 2021 |
| Luso Architecture Ltd | Professional & scientific | 2022 |
| Luxor Plumbing & Heating Services Ltd | Construction | 2026 |
| Luxor Properties Group Ltd | Construction | 2025 |
| Luxury Little Rooms Limited | Extraterritorial | 2012 |
| LW Holdings (International) Ltd | Real estate | 2017 |
| Lydia Nails Ltd | Other services | 2026 |
| Lymington PUB Co Ltd | Hospitality | 2025 |
| M & D Tooling Limited | Manufacturing | 2014 |
| M G Norman & Co Ltd | Financial services | 2002 |
| M J Hayler Construction Services Limited | Administrative & support | 2016 |
| M&O Hospitality Ltd | Hospitality | 2026 |
| M.V.M. Sheet Metal Fabrications Limited | Manufacturing | 1966 |
| MA Planning Services Limited | Professional & scientific | 2021 |
| MAC Supplies Limited | Wholesale & retail | 2011 |
| Macey Management Limited | Professional & scientific | 2026 |
| Mach 2 Engineering Limited | Manufacturing | 1997 |
| Macy Services Limited | Financial services | 2018 |
| Maddox Hair Limited | Other services | 2020 |
| Made Limited | Information & communication | 2022 |
| Maia Growth Partners Ltd | Professional & scientific | 2021 |
| Maja Group Ltd | Financial services | 2026 |
| Makester Ltd | Wholesale & retail | 2020 |
| Makrocare UK Ltd | Professional & scientific | 2012 |
| Mallards Leisure LLP | | 2021 |
| Mallorca Yacht Management Ltd | Professional & scientific | 2024 |
| Malthouse Healthcare Limited | Health & social care | 2005 |
| MAN & Bear Limited | Wholesale & retail | 2014 |
| Mandir Ltd | Hospitality | 2024 |
| Manor House School Trust Limited | Education | 1959 |
| Mansell Developments Ltd | Real estate | 2019 |
| Mantaplan Limited | Arts & recreation | 1983 |
| Manufacturing Software Consultancy Limited | Information & communication | 1995 |
| Maple Maintenance & Construction Ltd | Administrative & support | 2017 |
| Marbari Management Limited | Real estate | 2016 |
| Marble, Granite, Quartz Kent Limited | Construction | 2013 |
| March Chemicals Co. (UK) Limited | Administrative & support | 2002 |
| Marco Pasolini Osteopathy Limited | Health & social care | 2017 |
| Marine Technology Limited | Administrative & support | 2008 |
| Marinelife | Education | 2004 |
| Marisco Electricals Limited | Construction | 2016 |
| Marisco South Limited | Construction | 2011 |
| Maritime Management (Sandbanks) Limited | Households | 1976 |
| Marjen Hospitality & Leisure Ltd | Hospitality | 2021 |
| Mark Anthony Home Improvements Limited | Construction | 2005 |
| Mark D Taylor Limited | Information & communication | 2025 |
| Mark Looker Rigging Services Limited | Arts & recreation | 2016 |
| Marketta Global Ltd | Professional & scientific | 2023 |
| Marks Fitzpatrick Gaule Limited | Professional & scientific | 2007 |
| Marrache Consultancy Limited | Professional & scientific | 2025 |
| Marshal Consultants Ltd | Information & communication | 2018 |
| Marshwood Properties Ltd | Construction | 2025 |
| Martyn Crossley Limited | Wholesale & retail | 2004 |
| Mason's DRY Cleaners and Laundry Services Ltd | Other services | 2017 |
| Mathews Investments Ltd | Other services | 2023 |
| Mauden Limited | Manufacturing | 1994 |
| Maverick 33 Ltd | Professional & scientific | 2024 |
| Maverick One One Three Limited | Professional & scientific | 2024 |
| Max-Q Holdings Limited | Wholesale & retail | 2021 |
| Maxx Trading (London) Ltd | Wholesale & retail | 2012 |
| Maya Restaurants Limited | Hospitality | 2003 |
| MB Carpentry & Design Solutions Ltd | Construction | 2025 |
| Mccall Automation Ltd | Construction | 2024 |
| Mccarthy & Churchill Ltd | Construction | 2026 |
| Mccarthy & Mccarthy Limited | Real estate | 2001 |
| Mccarthy Investments Limited | Real estate | 2006 |
| Mccarthy Living Ltd | Construction | 2026 |
| Mccarthy Retirement Homes Limited | Real estate | 1999 |
| Mccarthy Retirement Limited | Real estate | 2002 |
| Mccarthy Retirement Living Limited | Real estate | 2002 |
| Mcj&Co Ltd | Wholesale & retail | 2025 |
| Mcphersons PM Ltd | Professional & scientific | 2015 |
| Mcphersons Project Services Limited | Professional & scientific | 1984 |
| Mcrw Gatwick (UK) LLP | | 2009 |
| Mcrw Holdings Limited | Professional & scientific | 2007 |
| Mcrw Service LLP | | 2009 |
| MDT Photography Limited | Professional & scientific | 2025 |
| Meadowview Property Group Ltd | Real estate | 2025 |
| Meci Solutions Ltd | Professional & scientific | 2019 |
| Medella Home Physio & OT Ltd | Health & social care | 2025 |
| Medstead Farm (Four Marks) Management Company Limited | Households | 2014 |
| Meed Electrical Ltd | Construction | 2020 |
| Meesons Solicitors Limited | Professional & scientific | 2012 |
| MEL Bush Organisation Limited | Administrative & support | 1973 |
| Melbury Court (Upton) Management Limited | Construction | 2019 |
| Melling Project Management Limited | Professional & scientific | 2004 |
| Mellors Heating & Cooling Ltd | Construction | 2025 |
| Melody Enterprise Limited | Transport & logistics | 2008 |
| Merch Makers Group Ltd | Wholesale & retail | 2025 |
| Mergeswift Property Management Limited | Households | 1991 |
| Meridian Van Racking Solutions Ltd | Manufacturing | 2020 |
| Merley Design & Construction Limited | Real estate | 1996 |
| Merlin Contracts and Developments Ltd | Construction | 2011 |
| Merlo UK Limited | Wholesale & retail | 1993 |
| Merryboon Limited | Administrative & support | 2008 |