| Makhosie Limited | Real estate | 2021 |
| Making Experiences Count Ltd. | Professional & scientific | 2008 |
| Makk Properties Limited | Real estate | 2005 |
| Malaysian Street Food Ltd | Hospitality | 2023 |
| Malkin Builders Limited | Construction | 2001 |
| MAM Transfers Ltd | Transport & logistics | 2025 |
| Mamba Manpower Limited | Information & communication | 2025 |
| Mamiq Ltd | Transport & logistics | 2016 |
| Manav Dental Care Ltd | Health & social care | 2025 |
| Mandaring Limited | Hospitality | 2020 |
| Mango Marketing Solutions Ltd | Other services | 2011 |
| Manila Store Limited | Wholesale & retail | 2022 |
| Manor Road Property Management Limited | Households | 2005 |
| Manorcod Limited | Hospitality | 2021 |
| Mantrasatyam Ltd | Wholesale & retail | 2024 |
| Maple-Roo Consulting (UK) Limited | Professional & scientific | 2018 |
| Marc James Bar Company Ltd | Hospitality | 2020 |
| Marca Services Limited | Administrative & support | 2022 |
| Marcu Trade Limited | Professional & scientific | 2016 |
| Marden ST Albans Limited | Construction | 2017 |
| Mareko Limited | Administrative & support | 2023 |
| Margaret Raymond Florist Ltd | Wholesale & retail | 2024 |
| Marhaba Restaurant Ltd | Hospitality | 2025 |
| Mariama Hair Ltd | Other services | 2022 |
| Marina Enterprises Limited | Real estate | 1999 |
| Marine Parade Leigh Limited | Real estate | 2023 |
| Mark Autos PVT Ltd | Wholesale & retail | 2026 |
| Mark Stafford Events Ltd | Administrative & support | 2025 |
| Marlowes Beauty Palace Ltd | Wholesale & retail | 2026 |
| Marmauke the Lion Property's Ltd | Real estate | 2019 |
| Marshawn Marketing Ltd | Professional & scientific | 2026 |
| Mashmin Ltd | Wholesale & retail | 2024 |
| Masterbell Communications Limited | Wholesale & retail | 1997 |
| Masters Lodge Freehold Company Limited | Households | 2017 |
| Masters Lodge Management Limited | Households | 1986 |
| Masters Lodge RTM Company Limited | Households | 2014 |
| Mathuka Ltd | Real estate | 2026 |
| Maxigain Limited | Wholesale & retail | 2019 |
| Maximax Accountants Limited | Professional & scientific | 2022 |
| Maximax Limited | Professional & scientific | 2013 |
| Maxine Barrow Limited | Other services | 2024 |
| MAY SEK Ltd | Hospitality | 2018 |
| Maydrew Limited | Hospitality | 2018 |
| Mayfair Technologies Limited | Information & communication | 2007 |
| Mayhew Mccrimmon Printers Limited | Manufacturing | 1978 |
| MB Barber Ltd | Other services | 2018 |
| MB London Consulting Ltd | Professional & scientific | 2023 |
| MBM Advisory Ltd | Information & communication | 2025 |
| MCB Accounting Ltd | Professional & scientific | 2014 |
| Mcbp Limited | Other services | 2018 |
| Mcginn’S Fishmongers Ltd | Manufacturing | 2026 |
| MCI & Sons Properties Ltd | Real estate | 2025 |
| Mcraed Limited | Health & social care | 2013 |
| MD Maintenance (London) Ltd | Construction | 2017 |
| ME Glow Ltd | Wholesale & retail | 2025 |
| Mead Foam Limited | Wholesale & retail | 2002 |
| Mead Properties Essex Limited | Real estate | 2021 |
| Meadline Limited | Real estate | 2001 |
| Med-Repat Service Ltd | Other services | 2025 |
| Medflow Solutions Ltd | Administrative & support | 2025 |
| Medifoot CPD School Ltd | Education | 2016 |
| Mehru Investments Limited | Real estate | 2025 |
| Mellius Ltd | Information & communication | 2017 |
| Melmar Properties Limited | Real estate | 2022 |
| Memory Care Hub Ltd | Health & social care | 2025 |
| Men's Health Kingston Limited | Health & social care | 2021 |
| MEP Recruitment Limited | Administrative & support | 2018 |
| MER Charging UK Limited | Transport & logistics | 2020 |
| Meric Care Ltd | Health & social care | 2023 |
| Metal & Plastics UK Ltd | Manufacturing | 2017 |
| Meteor Estates Ltd | Real estate | 2025 |
| Meteor Rest Home Limited | Health & social care | 2016 |
| MG Ceilings and Partitions Limited | Construction | 2003 |
| MG Delicatessen Limited | Wholesale & retail | 2025 |
| MGS Glass Partitioning Ltd | Construction | 2023 |
| Mhelectricalmaintenanceservices Ltd | Manufacturing | 2025 |
| Mhwc Ltd | Real estate | 2023 |
| MIA SOL Fashion Jewellery Collection Ltd | Manufacturing | 2025 |
| Michelle Freehold Management Company Limited | Hospitality | 2013 |
| Microblading Southend Limited | Other services | 2022 |
| Migefra Consultancy Ltd | Professional & scientific | 2019 |
| Mighty T Ltd | Manufacturing | 2025 |
| Mile and a Third Limited | Hospitality | 2018 |
| Miles Contracting Limited | Construction | 2011 |
| Milestone Accommodations Ltd | Construction | 2024 |
| Milk and Honey Swim Ltd | Wholesale & retail | 2024 |
| Milpen Ltd | Information & communication | 2020 |
| Mina Fast Food Limited | Hospitality | 2026 |
| Mind State Black Ltd | Wholesale & retail | 2023 |
| Minimanandme Ltd | Wholesale & retail | 2025 |
| Minty Card Company Ltd | Wholesale & retail | 2025 |
| Minvielle House Ltd | Real estate | 2025 |
| Mira DAS House Ltd | Wholesale & retail | 2024 |
| Mirana Accountancy Limited | Professional & scientific | 2026 |
| Mirosped Limited | Transport & logistics | 2017 |
| Miskos Ltd | Information & communication | 2013 |
| Miss AJ Boutique Ltd | Manufacturing | 2016 |
| Mist Productions Ltd | Wholesale & retail | 2018 |
| Mitrica Trans Ltd | Transport & logistics | 2021 |
| MIU Tran Nails Ltd | Other services | 2025 |