| Mccoll Surveys Ltd | Professional & scientific | 2022 |
| Mcennis Evans Consultancy Ltd | Professional & scientific | 2013 |
| Mckay Building Consultancy Ltd | Construction | 2025 |
| Mcmag Limited | Real estate | 2022 |
| Mcnally and Associates Limited | Administrative & support | 2025 |
| Mcneill Vineyard Management Limited | Agriculture & fishing | 2011 |
| MCP Insulation Ltd | Construction | 2015 |
| Mcpressy Ltd | Professional & scientific | 2018 |
| Mcqueen Property Investments Limited | Real estate | 2017 |
| MCS Building & Refurb Services Ltd | Construction | 2024 |
| Mctigue and Lewis Ltd | Construction | 2023 |
| MCW Contracting Limited | Administrative & support | 2011 |
| MD Tiling & Bathrooms Limited | Construction | 2017 |
| MDJ UK Group Ltd | Construction | 2024 |
| MDL Delivery Consultants Ltd | Professional & scientific | 2023 |
| MDP Building Ltd | Construction | 2018 |
| ME Currency Management Ltd | Financial services | 2022 |
| ME7 Global Limited | Professional & scientific | 2020 |
| ME7 Limited | Professional & scientific | 2009 |
| MEA Consulting Limited | Professional & scientific | 1998 |
| Meach Limited | Financial services | 2018 |
| Meadow Construction Management Ltd | Construction | 2025 |
| Meads Minis Autos Ltd | Wholesale & retail | 2026 |
| Meadway Construction 1982 Ltd | Other services | 2024 |
| MEC Facilities Management Limited | Construction | 2020 |
| MEC Security Limited | Administrative & support | 2012 |
| Mec-Tech Essex Ltd | Energy | 2021 |
| Mecen Group UK Ltd | Wholesale & retail | 2026 |
| Media House Holdings Limited | Professional & scientific | 2002 |
| Medical Consult Ltd | Health & social care | 2018 |
| Medical Diagnostic & Treatment Solutions Limited | Health & social care | 2007 |
| Meek Accountancy Services Limited | Professional & scientific | 2024 |
| Meera K Group Ltd | Professional & scientific | 2012 |
| MEH Engineering Limited | Administrative & support | 2003 |
| Mehmet & Akile Property Limited | Real estate | 2023 |
| MEL Skinner Electrical Services Limited | Construction | 2005 |
| Melir Group Limited | Financial services | 2022 |
| Melvue Holdings Ltd | Financial services | 2025 |
| Melwood Publishing Ltd | Information & communication | 2020 |
| MEM1 Limited | Hospitality | 2023 |
| Mentys Ltd | Professional & scientific | 2015 |
| Meral's Brew Cafe Ltd | Hospitality | 2025 |
| Merchant and SON Electrical Limited | Construction | 2018 |
| Mercury Car Centre Limited | Wholesale & retail | 2005 |
| Mercury Electrical Installations Ltd | Construction | 2006 |
| Meritocracy Limited | Real estate | 2010 |
| Merseyside Flag Limited | Professional & scientific | 2006 |
| Meta Metal Prints Ltd | Manufacturing | 2024 |
| Meta.Recruitment Ltd | Administrative & support | 2019 |
| Metaclip Ltd | Professional & scientific | 2026 |
| Metaverse for Cash Ltd | Information & communication | 2023 |
| Metaverse for Money Ltd | Information & communication | 2023 |
| Metch Holdings Ltd | Real estate | 2024 |
| Metis 978 Consulting Limited | Administrative & support | 2018 |
| Mezzequity Limited | Financial services | 2022 |
| MH Electrical Solutions Limited | Construction | 2007 |
| MI Pixel Ltd | Information & communication | 2021 |
| Michael Bacon Residential Ltd | Real estate | 2021 |
| Michael Letch & Partners LLP | | 2007 |
| Michael Pearson Hairdressing Limited | Other services | 2020 |
| Michelle's Beauty Rooms Limited | Other services | 2011 |
| Micky Flints Limited | Administrative & support | 2011 |
| Midd Technologies Ltd | Information & communication | 2014 |
| Middleton Holdings (Essex) Limited | Real estate | 2024 |
| Miguel's Cocina Ltd | Manufacturing | 2025 |
| Mihris Limited | Professional & scientific | 2022 |
| Mikecon Properties Limited | Real estate | 2013 |
| Mile END Maintenance Ltd | Construction | 2025 |
| Mileham Electrical Contract Services Limited | Construction | 2015 |
| Millbrook Consulting Partners Limited | Administrative & support | 2020 |
| Miller & Miller Associates Limited | Administrative & support | 2022 |
| Millers Properties Ltd | Real estate | 2023 |
| Millott Ltd | Construction | 2025 |
| Millview Property LLP | | 2026 |
| Mime Consultancy Limited | Professional & scientific | 2021 |
| Minaret (UK) Limited | Real estate | 1998 |
| Minchenden Limited | Real estate | 2015 |
| Mintcase Limited | Administrative & support | 2026 |
| Mirage RC Ltd | Manufacturing | 2021 |
| Miraii Limited | Information & communication | 2023 |
| Mirencliff Limited | Hospitality | 1993 |
| Mishka Healthcare Ltd | Health & social care | 2016 |
| Mishka Properties Ltd | Real estate | 2021 |
| Mix-N-Go Ready MIX Concrete Essex Ltd | Construction | 2026 |
| MJ Fencing Limited | Construction | 2008 |
| MJ Ferguson Services Limited | Construction | 2014 |
| MJ Investing Ltd | Construction | 2026 |
| MJB Property Collective Ltd | Real estate | 2025 |
| MJC Pipelines Limited | Construction | 2026 |
| MJH Construction Services Ltd | Construction | 2022 |
| MJL International Ltd | Administrative & support | 2023 |
| MJN Plants Ltd | Administrative & support | 2025 |
| MJO Consulting Ltd | Administrative & support | 2026 |
| MJS Consultancy Services Ltd | Professional & scientific | 2023 |
| MJS Online Limited | Wholesale & retail | 2014 |
| MJW Photography Ltd | Professional & scientific | 2024 |
| MK INT Holdings Ltd | Professional & scientific | 2023 |
| MK Mgmt Ltd | Hospitality | 2024 |
| MK Publications (UK) Limited | Information & communication | 2002 |
| MKC Rentals Limited | Real estate | 2024 |