| Media Spread Inc Limited | Professional & scientific | 2013 |
| Medic Express Ltd | Health & social care | 2015 |
| Medivape Ltd | Wholesale & retail | 2025 |
| Meek Investment Ltd | Health & social care | 2014 |
| Mega Camps Ltd | Health & social care | 2013 |
| Mega Marquees Limited | Administrative & support | 2013 |
| Mehta Medical Ltd | Professional & scientific | 2011 |
| Meikle Building Services Limited | Construction | 2015 |
| Meirik Investments Ltd | Real estate | 2022 |
| Mela Verde Limited | Hospitality | 2023 |
| Melanie Court Limited | Real estate | 2017 |
| Melon Holdings Limited | Real estate | 2026 |
| MEM Fish 27 Ltd | Hospitality | 2025 |
| Members House Ltd | Manufacturing | 2026 |
| Mensah Investments Ltd | Financial services | 2025 |
| Merchants Way Management Company Limited | Households | 2008 |
| Merchly Accessories Ltd | Wholesale & retail | 2025 |
| Mercy Prevail Healthcare Services Ltd | Health & social care | 2021 |
| Mercycare and Outreach Support Ltd | Hospitality | 2023 |
| Meredith O'Neill Design Ltd | Professional & scientific | 2025 |
| Merlin South East Limited | Real estate | 2004 |
| Merlin Transfers Limited | Manufacturing | 1994 |
| Mermaid International Ltd | Administrative & support | 2021 |
| Mermut & SON Ltd | Hospitality | 2019 |
| Messy Art Club Limited | Wholesale & retail | 2025 |
| META4MEDIA Limited | Information & communication | 2023 |
| Metal Signs Limited | Extraterritorial | 2023 |
| Metalite Water Hygiene Limited | Water & waste | 2025 |
| Metis Rail Ltd | Construction | 2023 |
| Metklean Products Limited | Manufacturing | 1986 |
| Metropolitan Grounds Maintenance Limited | Administrative & support | 2014 |
| Mewa (Multicultural Essex Women Association) CIC | Education | 2025 |
| MF Legacy Limited | Information & communication | 2023 |
| MFT Fulfillment Centre International Ltd | Transport & logistics | 2023 |
| MG Group Solutions Ltd | Transport & logistics | 2025 |
| MGR Plastering & Building Ltd | Construction | 2021 |
| Mguz Limited | Health & social care | 2019 |
| MH Energy Solutions Limited | Professional & scientific | 2021 |
| MHL Property Holdings Limited | Real estate | 2021 |
| Miah and Sons Property Ltd | Real estate | 2019 |
| Miawood Developments Limited | Real estate | 2018 |
| Miawood Properties Limited | Real estate | 2016 |
| Michael Robert WIG & Hair Piece Centre Ltd | Other services | 2003 |
| Michael Thomas Ltd | Construction | 2025 |
| Michaeon Limited | Professional & scientific | 2023 |
| Michelle Elliott-Britto Interiors Limited | Professional & scientific | 2020 |
| Michelle Mackie Limited | Arts & recreation | 2019 |
| Mickling Mcguire Limited | Real estate | 2018 |
| Micro Advertising Limited | Professional & scientific | 2011 |
| Microtec EDM Limited | Manufacturing | 2001 |
| Microtec Machining Limited | Real estate | 2009 |
| Microtec Precision Plan Ltd | Information & communication | 2022 |
| Midastouch Healthcare Ltd | Health & social care | 2024 |
| Miju Ltd | Information & communication | 2021 |
| Mill Lodge Shoeburyness RTM Company Ltd | Households | 2014 |
| Millag Limited | Real estate | 2025 |
| Millbrooke Stone Ltd | Manufacturing | 2017 |
| Millennium TCT Trading Ltd | Wholesale & retail | 2018 |
| Millfields (CAM) Management Company Limited | Households | 2019 |
| Millview Property Investments Limited | Real estate | 2022 |
| Millworks, K Langley Management Company Limited | Households | 2023 |
| Miltons of Pimlico Holding Limited | Financial services | 2023 |
| Miltons of Pimlico Properties Limited | Real estate | 2020 |
| Mime the GAP Limited | Arts & recreation | 2017 |
| Mina Children and Family Support Limited | Health & social care | 2024 |
| Mina Medical Ltd | Health & social care | 2020 |
| Mind Your Language Limited | Education | 2020 |
| Mine Academy Limited | Other services | 2025 |
| Mined Records Ltd | Information & communication | 2026 |
| Minira Medical Ltd | Health & social care | 2019 |
| Miru 3D Limited | Information & communication | 2018 |
| Miss Roo's Emporium Ltd | Wholesale & retail | 2021 |
| Mistry & Sons Limited | Financial services | 2014 |
| Mivas Investments Ltd | Real estate | 2021 |
| Mizooz Limited | Wholesale & retail | 2020 |
| MJ Brenson Limited | Transport & logistics | 2018 |
| MJA Car Sales Limited | Administrative & support | 1998 |
| MJD Planning Ltd | Professional & scientific | 2021 |
| Mjeb Limited | Professional & scientific | 2015 |
| Mjms Southend Food Limited | Hospitality | 2026 |
| MJP Management Services Limited | Financial services | 2021 |
| MK Lifestyled Ltd | Health & social care | 2017 |
| MKT Developments Limited | Construction | 2026 |
| MKU Group Limited | Hospitality | 2023 |
| MKZ Essential Ltd | Wholesale & retail | 2026 |
| MLB Law Ltd | Professional & scientific | 2024 |
| MLG Motors Ltd | Wholesale & retail | 2025 |
| MLK Security Ltd | Administrative & support | 2024 |
| MLK UK Traders Ltd | Wholesale & retail | 2024 |
| MM Food Services Limited | Wholesale & retail | 2024 |
| MM Mihaylov Marketing Ltd | Wholesale & retail | 2020 |
| MM2 Mobile Tyres Ltd | Wholesale & retail | 2024 |
| Mmakaira Limited | Financial services | 2017 |
| MMP Neuro Services Ltd | Health & social care | 2022 |
| MN 4 Construction Limited | Construction | 2023 |
| MNM Collects Ltd | Wholesale & retail | 2025 |
| MNM Professionals Limited | Education | 2022 |
| MNS World Limited | Real estate | 2026 |
| Mobeft Limited | Extraterritorial | 1988 |
| Mobile EAR Syringing Ltd | Health & social care | 2019 |