| Mary ‘Mole Limited | Wholesale & retail | 2025 |
| Masha Enterprise International Limited | Wholesale & retail | 2024 |
| Masonridge Limited | Real estate | 2025 |
| Mastercraft Tile Ltd | Construction | 2026 |
| Masters Investments Limited | Education | 2020 |
| Mastery & Miles Ltd | Information & communication | 2025 |
| Matandmel Limited | Education | 2010 |
| Matrixes Ltd | Wholesale & retail | 2023 |
| Matthews Plumbing & Heating Solutions Ltd | Construction | 2018 |
| Mattiro Ltd | Construction | 2020 |
| Mattis Faith & White Rose Solicitors and Advocates Ltd | Professional & scientific | 2025 |
| Matts Consulting Ltd | Administrative & support | 2024 |
| Maverick Kole Investments Ltd | Real estate | 2020 |
| Maximusmarketing Ltd | Professional & scientific | 2025 |
| Maxmaso Enterprises Ltd | Real estate | 2026 |
| MAY & MOY Business Services Ltd | Professional & scientific | 2015 |
| May/Be Creative Ltd | Professional & scientific | 2025 |
| Mayadan Electrical Limited | Construction | 2015 |
| Maybarskan Ltd | Hospitality | 2022 |
| Maye Care Ltd | Public administration | 2018 |
| Maytop Limited | Administrative & support | 2021 |
| MAZ Property Investments Limited | Real estate | 2022 |
| Mazati Solutions Limited | Information & communication | 2013 |
| MC66 Ltd | Arts & recreation | 2024 |
| Mcneil Technologies Limited | Information & communication | 2025 |
| Mcnulty Equity Limited | Financial services | 2021 |
| Mcnulty Group Limited | Financial services | 2026 |
| MCS Hair & Nail Bar Ltd | Other services | 2025 |
| Mcseal Consulting Limited | Information & communication | 2022 |
| Mealtime Limited | Manufacturing | 2020 |
| Meccanico Developments Ltd | Construction | 2022 |
| Mechanical & Ferrous Limited | Administrative & support | 1986 |
| Medallion Plastics Fabrications Ltd | Construction | 2017 |
| Medallion Plastics Limited | Construction | 1985 |
| Medhurst Funeral Directors Ltd | Other services | 2026 |
| Medile Ltd | Health & social care | 2024 |
| Medplus Services Limited | Health & social care | 2015 |
| Medport Global Consultancy Limited | Professional & scientific | 2023 |
| Medport Global Estate Development Limited | Real estate | 2025 |
| Medport Global Limited | Construction | 2018 |
| Medwear Academy Limited | Manufacturing | 2025 |
| Mega Decorators Ltd | Construction | 2019 |
| Megacrown Holdings UK Ltd | Wholesale & retail | 2022 |
| Megaregal (UK) Ltd | Information & communication | 2017 |
| Megz Care Limited | Health & social care | 2019 |
| Meley Trading Ltd | Other services | 2020 |
| Melrose Academy Ltd | Education | 2024 |
| Mended Fencing Ltd | Other services | 2018 |
| Merav Group Ltd | Information & communication | 2022 |
| Mercy Hephzibah Beulah Limited | Real estate | 2024 |
| Merghanis Engineering Ltd | Manufacturing | 2018 |
| Meridian Technical Services Limited | Water & waste | 1994 |
| Metajam Ltd | Information & communication | 2016 |
| Metal Works (London) Limited | Construction | 2011 |
| Metalicoroofing Ltd | Construction | 2026 |
| Metaslead Limited | Information & communication | 2016 |
| Metrocom Consulting Limited | Professional & scientific | 2010 |
| Metros West Street Ltd | Hospitality | 2023 |
| Metst Unique Ltd | Health & social care | 2023 |
| Meyer Construction Ltd | Construction | 2023 |
| MFM Triumphant Church Ltd | Other services | 2024 |
| Mhik Ltd | Wholesale & retail | 2025 |
| MHL Services Limited | Administrative & support | 2023 |
| MHZ Engineering Ltd | Construction | 2026 |
| Micprotect Security Limited | Administrative & support | 2025 |
| Midaky Ltd | Wholesale & retail | 2020 |
| Midefat Consultant UK Ltd | Other services | 2019 |
| Mideshealth Limited | Health & social care | 2015 |
| Midfir Services Limited | Health & social care | 2014 |
| Midnight Lights Ltd. | Arts & recreation | 2014 |
| Midsally Limited | Health & social care | 2022 |
| MIF Global Ltd | Wholesale & retail | 2016 |
| Migrace Support Services Ltd | Administrative & support | 2025 |
| Mikeglobals Services Limited | Construction | 2016 |
| Mikeporsh Limited | Construction | 2013 |
| MILE12MART Ltd | Wholesale & retail | 2025 |
| Mill Road Cafe Ltd | Hospitality | 2024 |
| Mill Road Local Store Ltd | Wholesale & retail | 2026 |
| Milton Electrics Ltd. | Manufacturing | 2016 |
| Mindful Heaven Limited | Transport & logistics | 2024 |
| Mindfulcreative Ltd | Wholesale & retail | 2025 |
| Mingos Mobile Catering Ltd | Hospitality | 2024 |
| Mini-Me Essentials Limited | Wholesale & retail | 2018 |
| Mint IT Limited | Administrative & support | 2011 |
| Miorhe Ltd | Wholesale & retail | 2026 |
| Mira Maya Ltd | Wholesale & retail | 2025 |
| Mirevic & Priema Services Ltd | Wholesale & retail | 2017 |
| Mitchell Framing Limited | Wholesale & retail | 2015 |
| Mitella Ltd | Wholesale & retail | 2025 |
| Mitho Bhansa Ltd | Wholesale & retail | 2023 |
| Mitojoso UK Limited | Real estate | 2023 |
| MJ Carpentry & Refurb Ltd | Construction | 2014 |
| Mj-Nelkon Professional Services Limited | Information & communication | 2025 |
| MJR Refurbishments Ltd | Construction | 2018 |
| Mj’S Sandwich Club Limited | Hospitality | 2025 |
| Mkandi Limited | Information & communication | 2017 |
| MKS Consults Limited | Information & communication | 2015 |
| MLP Collective Ltd | Information & communication | 2025 |
| MM Tiling and Flooring Ltd | Construction | 2022 |
| MMC Brothers Limited | Hospitality | 2019 |