| Manifest Capital Property Investments Ltd | Real estate | 2022 |
| Manifold Technologies Limited | Information & communication | 2025 |
| Manis Child Care Ltd | Health & social care | 2017 |
| Manjit Sehmby Ltd | Health & social care | 2012 |
| Mann Consultancy Services Ltd | Information & communication | 2016 |
| Manonasa Media & Entertainment Ltd | Arts & recreation | 2025 |
| Manor Build London Limited | Construction | 2021 |
| Mansoor Butt | Health & social care | 2006 |
| Manteau Noir Limited | Professional & scientific | 2025 |
| Mantra Consulting Services Limited | Administrative & support | 2015 |
| Mantra Management Limited | Real estate | 2025 |
| Mantra Property Services Limited | Construction | 2020 |
| MAP Interiors Holdings Limited | Financial services | 2014 |
| MAP Interiors Ltd | Construction | 2008 |
| Maple Square Properties Limited | Real estate | 2018 |
| Maples London Limited | Hospitality | 2022 |
| Mapsi Store Limited | Wholesale & retail | 2017 |
| Marabim Limited | Public administration | 2022 |
| Marbelon City Ltd | Hospitality | 2024 |
| Marbelon Hospitality Ltd | Hospitality | 2024 |
| Marbelon Ltd | Hospitality | 2022 |
| Marbelon Restaurants Ltd | Hospitality | 2024 |
| Marc Thurlow Associates Limited | Financial services | 2021 |
| Marcus & Reconstruction Ltd | Construction | 2014 |
| Marcus Foster Limited | Administrative & support | 2015 |
| Mardan Investments Ltd | Real estate | 2017 |
| Mardan Properties Limited | Real estate | 2003 |
| Mardan Services Ltd | Real estate | 2017 |
| Marina Crescent 2 Ltd | Real estate | 2025 |
| Mario Recovery Limited | Transport & logistics | 2018 |
| Marios Schwab Limited | Administrative & support | 2006 |
| Mariposa Holdings Ltd | Financial services | 2026 |
| Marito Ventures Limited | Real estate | 2025 |
| Mark Fast Food Ltd | Hospitality | 2023 |
| Mark Kayes Ltd | Arts & recreation | 2025 |
| Market Logistics East Ltd | Professional & scientific | 2018 |
| Market Provisions (Smithfield) Limited | Wholesale & retail | 1990 |
| Marla Hair Limited | Other services | 2018 |
| Marm Services Ltd | Professional & scientific | 2021 |
| Marpaul (Tonbridge 1) Limited | Real estate | 2022 |
| Marpaul (Tonbridge 2) Limited | Real estate | 2022 |
| Marpaul (Tonbridge 3) Limited | Real estate | 2022 |
| Marpaul Construction Limited | Professional & scientific | 2016 |
| Marpaul Group Limited | Professional & scientific | 1985 |
| Marpaul Hampshire Limited | Real estate | 2016 |
| Marpaul Holdings Limited | Construction | 1983 |
| Marpaul Limited | Real estate | 1983 |
| Marpaul London Limited | Construction | 1971 |
| Marpaul Management Limited | Real estate | 2016 |
| Marpaul Southern Limited | Construction | 1979 |
| Marpaul Sports CIC | Extraterritorial | 2008 |
| Marq Properties Limited | Real estate | 2021 |
| Mars Building Services Limited | Construction | 2016 |
| Marseil Limited | Real estate | 2025 |
| Marsii Ltd | Hospitality | 2019 |
| Martin Smith Property Management Limited | Real estate | 2014 |
| Martos Indalo Limited | Health & social care | 2012 |
| Maruti Trading Ltd | Manufacturing | 2025 |
| Marvelous Care at Solace LLP | | 2025 |
| MAS Motor Ltd | Wholesale & retail | 2024 |
| MAS Rental Properties Limited | Real estate | 2020 |
| Masalla Kitchen Limited | Hospitality | 2022 |
| Masalux Ltd | Hospitality | 2025 |
| Mascott London Ltd | Wholesale & retail | 2022 |
| Masett Helios Limited | Manufacturing | 2024 |
| Masha Consultancy Limited | Information & communication | 2024 |
| Masia Holdings Ltd | Financial services | 2025 |
| Masons Car Service Limited | Transport & logistics | 2013 |
| Mastaplasta Ltd | Wholesale & retail | 2009 |
| Master Beauty Limited | Wholesale & retail | 2018 |
| Master Chef Xpress Ltd | Hospitality | 2020 |
| Master Habitat Limited | Construction | 2020 |
| Master Locksmiths & Security Services Company Limited | Other services | 2004 |
| Masterfix Construction Ltd. | Construction | 2010 |
| Mastery Science Ltd | Information & communication | 2008 |
| Masvd Construction Ltd | Construction | 2013 |
| Matriarch Limited | Administrative & support | 2025 |
| Matt Dean Ltd | Administrative & support | 2024 |
| Maury Sewing Machine Company Limited | Hospitality | 1961 |
| Maverick One-Two Ltd | Hospitality | 2024 |
| Maverick Undertakings Limited | Wholesale & retail | 2023 |
| Mavion Group Limited | Construction | 2015 |
| Mavs Property Ltd | Administrative & support | 2018 |
| MAX Artin Consultancy Ltd | Professional & scientific | 2013 |
| MAX1-TRANSPORT Ltd | Water & waste | 2018 |
| Maxwell Care Ltd. | Administrative & support | 2025 |
| Maxximus Global Relocations Limited | Hospitality | 2022 |
| Mayday Enterprises Limited | Information & communication | 2004 |
| Maypole Gardens (Hainault) NO. 2 Residents Company Limited | Households | 1987 |
| Mayr London Limited | Health & social care | 2019 |
| Mayrose Properties Limited | Extraterritorial | 2018 |
| Mayspace Homes Limited | Real estate | 2025 |
| Mayville Electrical Ltd | Construction | 2018 |
| Mazolof U K Limited | Real estate | 2022 |
| Mazz Murray Limited | Arts & recreation | 2019 |
| MB Active Builders Ltd | Construction | 2025 |
| MB Brickwork Ltd | Administrative & support | 2017 |
| Mbmh Limited | Professional & scientific | 2024 |
| MC Cables & Subsea Ltd | Professional & scientific | 2023 |
| MC Expert Ltd | Construction | 2016 |