| Mainstreamtek UK Ltd | Information & communication | 2022 |
| Maintenance Direct Insurance Services Ltd. | Financial services | 1996 |
| Maintenance Direct Ltd. | Other services | 2016 |
| Maintenance Resolved Limited | Construction | 2025 |
| Mairaj Signatures Limited | Wholesale & retail | 2019 |
| Maison Asheka London Ltd | Manufacturing | 2025 |
| Maison DE Sérenne Ltd | Manufacturing | 2026 |
| Maison Prestige Realty Limited | Real estate | 2025 |
| Maitland Drive Limited | Real estate | 1988 |
| Majestic Concierge Ltd | Administrative & support | 2026 |
| Majha Fresh Imports Ltd | Wholesale & retail | 2023 |
| Majid&Sons Ltd | Wholesale & retail | 2025 |
| Major TOM Holdings Limited | Professional & scientific | 2022 |
| MAK Electrical Wholesalers Limited | Wholesale & retail | 1995 |
| MAK Property & Management Ltd | Wholesale & retail | 2024 |
| Make a Wish Cookies and Cake Ltd | Manufacturing | 2025 |
| Makemepreety Limited | Other services | 2022 |
| Makes Management Ltd | Professional & scientific | 2026 |
| Mako Logistics (UK) Limited | Transport & logistics | 2008 |
| Mako Maintenance Limited | Transport & logistics | 2011 |
| Mako Recruitment UK Ltd | Administrative & support | 2024 |
| Mako World Foods Ltd | Wholesale & retail | 2019 |
| Makr Projects Ltd | Construction | 2023 |
| Maksims Pakulis Ltd | Construction | 2025 |
| Malamlela Limited | Health & social care | 2017 |
| Malart Limited | Wholesale & retail | 2024 |
| Malgary Ltd | Wholesale & retail | 2024 |
| Malgary Studio Ltd | Professional & scientific | 2025 |
| Malik GPT Limited | Real estate | 2025 |
| Malik Homes Limited | Real estate | 2020 |
| Malik NM Logistics Limited | Transport & logistics | 2025 |
| Malik Projects Limited | Construction | 2023 |
| Mallard Court (Rickmansworth) Management Company Limited | Households | 1995 |
| Malpas Village Retail Limited | Wholesale & retail | 2025 |
| Malthouse Pharmacy Ltd | Wholesale & retail | 2006 |
| Mamma MIA Pizza and Kebab Ltd | Hospitality | 2018 |
| Mamy Cleaning Limited | Administrative & support | 2026 |
| Management Company (Garboldisham) Limited | Households | 2025 |
| Manakamana Enterprises Limited | Information & communication | 2019 |
| Mananzai Ltd | Wholesale & retail | 2020 |
| Mancipatio BH Limited | Real estate | 2025 |
| Mandeep Saund Ltd | Wholesale & retail | 2026 |
| Mane Car Storage Ltd | Transport & logistics | 2025 |
| Mane Production Limited | Arts & recreation | 2012 |
| Mango Hospitality Limited | Other services | 2025 |
| Mango Morriston Ltd | Financial services | 2012 |
| Mango Pharmacy Limited | Wholesale & retail | 2010 |
| Mangui & Co Import Export Ltd | Wholesale & retail | 2019 |
| Manii K Holdings Ltd | Transport & logistics | 2023 |
| Manish Driving Ltd | Education | 2022 |
| Manjeet Singh Construction Ltd | Construction | 2024 |
| Manmeet Construction and Design Ltd | Construction | 2025 |
| Manmin Ltd | Real estate | 2024 |
| Mann Productions Limited | Arts & recreation | 2013 |
| Manna Trading Ltd | Real estate | 2019 |
| Mannar Food Ltd | Hospitality | 2025 |
| Manning Services Limited | Administrative & support | 2016 |
| Manny Business Solutions Limited | Transport & logistics | 2011 |
| Manor View Residents Management Limited | Real estate | 1986 |
| Manor Waye Management Company Limited | Hospitality | 2012 |
| Manorhouse Services Limited | Financial services | 2020 |
| Manorwise Limited | Real estate | 1990 |
| Manpower Holdings (UK) Limited | Financial services | 2019 |
| Manpower IT Services Limited | Professional & scientific | 1990 |
| Manpower Nominees Limited | Professional & scientific | 1992 |
| Manpower Services Limited | Administrative & support | 1968 |
| Manpower UK Limited | Administrative & support | 1999 |
| Manpowergroup Digital Holdings Ltd | Financial services | 2017 |
| Manpowergroup Financing UK Ltd | Administrative & support | 2024 |
| Manpowergroup UK Limited | Professional & scientific | 1956 |
| Manrai Limited | Real estate | 2024 |
| Manri Accountancy Ltd | Professional & scientific | 2013 |
| Manrose Paint and Decore Ltd | Construction | 2025 |
| Mansha & Sons Limited | Wholesale & retail | 2025 |
| Mantiqueira UK I Holding Ltd | Financial services | 2025 |
| Mantiqueira UK II Holding Ltd | Financial services | 2025 |
| Mapcargo International Limited | Transport & logistics | 1995 |
| Mapcargo Logistics LLP | | 2005 |
| Maplebridge Limited | Other services | 1977 |
| Maplepecan Limited | Real estate | 2021 |
| Maples Management Limited | Households | 1990 |
| Mappa Ltd | Administrative & support | 2024 |
| MAR Trans Logistics Ltd | Transport & logistics | 2016 |
| MAR UK Trading Ltd | Wholesale & retail | 2019 |
| Marco Business Group Ltd | Wholesale & retail | 2020 |
| Margam Evans Limited | Wholesale & retail | 2004 |
| Margaret Pratt SPV 1 Ltd | Real estate | 2025 |
| Mario Services Ltd | Transport & logistics | 2019 |
| Marius Building Ltd | Construction | 2020 |
| Mark Rail Solutions Ltd | Professional & scientific | 2026 |
| Mark Sparks Electrical Ltd | Construction | 2018 |
| Mark Taylor Design Limited | Professional & scientific | 1996 |
| Mark Turner Property Services Limited | Construction | 2016 |
| Mark&Daniel Property Management Ltd | Real estate | 2025 |
| Market Factory Limited | Information & communication | 2009 |
| Marketing for Professionals Ltd | Professional & scientific | 2018 |
| Markety Limited | Information & communication | 2023 |
| Marlborough Court Management Company (Slough) Limited | Real estate | 1991 |
| Marlborough Road 23121960 Limited | Extraterritorial | 2013 |
| Marlex Construction Limited | Construction | 2017 |