| M&F Technical Services Ltd | Construction | 2022 |
| M&G Key Ventures Limited | Construction | 2025 |
| M&J Acoustic Limited | Arts & recreation | 2022 |
| M&K Films Ltd | Information & communication | 2024 |
| M&K Holdings (Worcestershire) Limited | Real estate | 2018 |
| M&M Personnel Ltd | Administrative & support | 2024 |
| M&M Real Estate Investment Ltd | Real estate | 2019 |
| M&P Properties Management Limited | Real estate | 2026 |
| M&S Portfolio & Ledger Limited | Real estate | 2025 |
| M-Delf, Civil Engineering Ltd | Construction | 2024 |
| M. J. Waldron Limited | Construction | 2002 |
| M.A.R Solicitors Limited | Professional & scientific | 2025 |
| M.A.Y Commercials Ltd | Households | 2025 |
| M.L.B. Electrical Contractors Limited | Construction | 2012 |
| M1 Builder Ltd | Construction | 2025 |
| M1 Management Services Limited | Administrative & support | 2006 |
| M2MSURFACE Ltd | Information & communication | 2020 |
| Maai Thai Ltd | Hospitality | 2026 |
| Maati Tech Technology Solutions Limited | Information & communication | 2023 |
| Mable Entertainment Limited | Extraterritorial | 1973 |
| MAC Europe Limited | Manufacturing | 2003 |
| Macca Consultancy Ltd | Construction | 2019 |
| Macdee Ltd | Real estate | 2022 |
| Macgregor Holdings Limited | Real estate | 2019 |
| Machine Capital Ltd | Administrative & support | 2024 |
| Machine Mind Partners Ltd | Information & communication | 2025 |
| Mack Estate Holdings Limited | Real estate | 2023 |
| Mackie's Commercial Cleaning Ltd | Administrative & support | 2022 |
| Mackies Cleaning Services Ltd | Administrative & support | 2021 |
| Mackin Thorne Homes Limited | Construction | 2026 |
| Macmillan & Mitchell Limited | Agriculture & fishing | 2022 |
| Mactush Resourcing Limited | Construction | 2017 |
| MAD PM Ltd | Real estate | 2025 |
| MAD Squirrel TAP Watford Ltd | Hospitality | 2021 |
| Madame’S Sugar Cookies Ltd | Manufacturing | 2020 |
| Made Leaders Next Generation CIC | Education | 2021 |
| Madee Ltd | Wholesale & retail | 2019 |
| MADEJUST4U Limited | Manufacturing | 2011 |
| Madeystock Greenlands Productions Ltd | Arts & recreation | 2025 |
| Madhouse Construction Ltd | Construction | 2026 |
| Madscapes Ltd | Administrative & support | 2022 |
| Madyfinance Services Ltd | Professional & scientific | 2023 |
| MAE Consult Ltd | Professional & scientific | 2022 |
| Maestro Renovations Limited | Real estate | 2025 |
| Magfer Ltd | Information & communication | 2019 |
| Magic Feet Essex Ltd | Arts & recreation | 2017 |
| Magik Nectar Ltd | Wholesale & retail | 2024 |
| Magneto Electrics Ltd | Manufacturing | 2021 |
| MAI Beauty Ltd | Other services | 2023 |
| Maia Healthcare Ltd | Health & social care | 2023 |
| Maidax Group Ltd | Administrative & support | 2024 |
| Maidenfields Estate Resident Management Company Ltd | Households | 2022 |
| Maids of Dockland Productions Ltd | Information & communication | 2017 |
| Mail Civils Ltd | Construction | 2025 |
| Mail Construction Ltd | Construction | 2022 |
| Mainarch Property Limited | Real estate | 2024 |
| Maitland Brickwork Ltd | Construction | 2016 |
| MAJ Tech Ltd | Professional & scientific | 2016 |
| Majac Limited | Financial services | 2014 |
| Majestic Tree Care Limited | Administrative & support | 2014 |
| Major Movement Entertainment Ltd | Administrative & support | 2018 |
| Makara Distribution Ltd | Transport & logistics | 2022 |
| Makersforge Ltd | Administrative & support | 2024 |
| Makki Upper Limb Doctor Limited | Health & social care | 2021 |
| Malcolm Clarke Limited | Wholesale & retail | 1956 |
| Malibu Bidco Limited | Financial services | 2023 |
| Malik Land Ltd | Financial services | 2025 |
| Maling Consultants Limited | Real estate | 2024 |
| Malithmec Ltd | Wholesale & retail | 2024 |
| Maliyah’S Chaii Limited | Hospitality | 2024 |
| Mallothi Limited | Information & communication | 2013 |
| Malobel Limited | Information & communication | 2011 |
| Mals Mobile Bar Ltd | Hospitality | 2026 |
| Mamarx Ltd | Real estate | 2025 |
| Mamba BJJ Limited | Arts & recreation | 2022 |
| Mamba Gym Limited | Arts & recreation | 2016 |
| Mamoli Limited | Extraterritorial | 2022 |
| MAN Plus Van London Ltd | Transport & logistics | 2020 |
| MAN Property Investments Ltd | Real estate | 2018 |
| Management Company Vine Court Limited | Households | 2021 |
| Manamou Limited | Wholesale & retail | 2013 |
| Manandhar Investments Limited | Real estate | 2021 |
| Manas Raps Ltd | Professional & scientific | 2023 |
| Manastate Limited | Households | 1983 |
| Mane Group Services Ltd | Construction | 2021 |
| Mangala Trading Company Limited | Professional & scientific | 2025 |
| Mangalmurtisaishakti One Stop Business Solutions Ltd | Professional & scientific | 2026 |
| Manhome Ltd | Households | 2021 |
| Mani Motors Ltd | Wholesale & retail | 2024 |
| Mani's Italian Kitchen Ltd | Hospitality | 2020 |
| Manor Court Management Company (Rainham) Limited | Households | 2021 |
| Manor Farm (Churwell) (NO.2) Management Company Limited | Households | 2003 |
| Manor Farm (Churwell) Management Company Limited | Households | 2002 |
| Manor Park (Rainham) Management Company Limited | Households | 2017 |
| Mansion Artists Management Ltd. | Arts & recreation | 2024 |
| Manufacturing Service Solutions Limited | Manufacturing | 2003 |
| Maple and Willow Management Company at Westley Green Limited | Households | 2023 |
| Maple Cleaning UK Limited | Administrative & support | 2024 |
| Maple Contract Cleaning Services Ltd | Extraterritorial | 2015 |
| Maple Creek Management Company Limited | Households | 2021 |