| Ma'At Professional Services Limited | Professional & scientific | 2021 |
| Ma's Kitchen Ltd | Hospitality | 2024 |
| Ma'Shales Services Ltd | Health & social care | 2025 |
| Ma.Gi.Mi Events Ltd | Hospitality | 2025 |
| Ma.Gi.Mi Ltd | Hospitality | 2018 |
| Ma.Gi.Mi Soho Ltd | Hospitality | 2024 |
| Ma.Gi.Mi TW9 Ltd | Hospitality | 2022 |
| MA20 Ltd | Wholesale & retail | 2015 |
| MAA & Associates Ltd | Transport & logistics | 2017 |
| MAA Developers Limited | Construction | 2022 |
| MAA Imaging Solutions Ltd | Health & social care | 2020 |
| Maahi Fast Food Limited | Hospitality | 2021 |
| Maahil Ltd | Wholesale & retail | 2018 |
| Maaj Group Limited | Construction | 2024 |
| Maam & Associates Ltd | Transport & logistics | 2024 |
| Maaruti Limited | Information & communication | 2020 |
| Mabs Care Ltd | Health & social care | 2022 |
| MAC Academic Ltd | Education | 2021 |
| MAC Home Improvements London Limited | Construction | 2018 |
| MAC Leda Limited | Professional & scientific | 2010 |
| MAC Plant Sales Ltd | Wholesale & retail | 2024 |
| MAC Plant Services Ltd | Administrative & support | 2021 |
| MAC Support London Ltd | Information & communication | 2013 |
| Mac's 2025 Ltd | Hospitality | 2025 |
| Mach 5 Developments Ltd | Construction | 2025 |
| Mach 5 Solutions Limited | Wholesale & retail | 2020 |
| Machan Kitchen Ltd | Hospitality | 2020 |
| Machine & Equipment Ltd | Manufacturing | 2014 |
| Machine Vending Services Limited | Administrative & support | 2010 |
| Macho Removals Ltd | Transport & logistics | 2023 |
| Machon (Beddington) Ltd | Real estate | 2014 |
| Mactribe Ltd | Information & communication | 2010 |
| Madaley Limited | Real estate | 2023 |
| Madan & Sons Limited | Wholesale & retail | 2002 |
| Maddalena 13 Ltd | Hospitality | 2018 |
| Maddox Buildings Ltd | Construction | 2020 |
| Maddy Properties Ltd | Real estate | 2020 |
| Made in Italy NW1 Ltd | Financial services | 2017 |
| Made YOU Fit Studio Limited | Education | 2025 |
| Madeira Construction Ltd | Construction | 2010 |
| Madhealthuk Ltd | Health & social care | 2026 |
| Madhvani Properties UK Limited | Real estate | 2017 |
| Madisan Limited | Wholesale & retail | 2021 |
| Madjam Limited | Professional & scientific | 2020 |
| Madyan Ltd | Health & social care | 2020 |
| Maestro Minds Ltd | Information & communication | 2021 |
| MAF Homes Ltd | Financial services | 2016 |
| MAF London Ltd | Hospitality | 2020 |
| Mafgo Services Ltd | Other services | 2019 |
| Maflora UK Ltd | Wholesale & retail | 2025 |
| Mafnaz Investments Limited | Construction | 2012 |
| Mafullerhealthcare Ltd | Administrative & support | 2017 |
| Magalino UK Limited | Financial services | 2021 |
| Magato Ltd | Construction | 2024 |
| Magdalen Mews Management Limited | Households | 2000 |
| Magdalene Carol (Productions) Limited | Information & communication | 2017 |
| Magdalene Carol Accessories Limited | Manufacturing | 2016 |
| Magenta Systems Limited | Information & communication | 1982 |
| Maggiemade Limited | Health & social care | 2015 |
| Magic Carpet Labs Limited | Arts & recreation | 2022 |
| Magic for Engineering Works Ltd | Manufacturing | 2023 |
| Magic Hour Agency Ltd | Information & communication | 2026 |
| Magic Marble Ltd | Construction | 2016 |
| Magic Model Agency London & Worldwide Limited | Arts & recreation | 2022 |
| Magical Cleaning Solutions Ltd | Administrative & support | 2025 |
| Magichabits Labs Limited | Information & communication | 2023 |
| Magicmydata Ltd | Information & communication | 2025 |
| Magicrock Consulting Ltd | Information & communication | 2025 |
| Magicturtle Ltd | Transport & logistics | 2017 |
| Magik Marketing Ltd | Wholesale & retail | 2019 |
| Magistrates House Management Limited | Households | 2019 |
| Magna Numeric Limited | Professional & scientific | 2006 |
| Magna Online Ltd | Wholesale & retail | 2024 |
| Magnificent Momentum Limited | Information & communication | 2019 |
| Magniski Ltd | Administrative & support | 2025 |
| Magnolia Court (Freehold) Limited | Households | 2004 |
| Magnolia Court (Sandy) Management Company Limited | Households | 2006 |
| Magpie Corporation Limited | Wholesale & retail | 2022 |
| Magymay Home Help Services Ltd | Health & social care | 2026 |
| MAH Catering Croydon Limited | Hospitality | 2018 |
| Maha Henna Studio Limited | Other services | 2025 |
| Maha Signature Homes Limited | Real estate | 2025 |
| Mahaboob & Co Ltd | Administrative & support | 2018 |
| Maharajah Properties Limited | Real estate | 2003 |
| Mahavir Packaging Industries Ltd | Wholesale & retail | 2026 |
| Maheen Uddin Limited | Health & social care | 2019 |
| Mahen Shan Prosper Limited | Administrative & support | 2017 |
| Mahi Mohan Limited | Other services | 2024 |
| Mahimo Ltd | Administrative & support | 2018 |
| Mahmood Niazi Enterprises Ltd | Wholesale & retail | 2025 |
| Mahoe Global Document Navigation Ltd | Administrative & support | 2026 |
| Maia Dome Limited | Financial services | 2026 |
| Maia Gray Ltd | Professional & scientific | 2022 |
| Maia Health and Beauty Limited | Wholesale & retail | 2011 |
| Maidstone Road Management Company Limited | Households | 2018 |
| Maiken Ltd | Wholesale & retail | 2021 |
| Mail My Nails Ltd | Wholesale & retail | 2021 |
| Maima Ltd | Other services | 2026 |
| Main House Management Limited | Households | 1981 |
| Mainline House Ltd | Households | 2018 |