| Mayhem Trading Ltd | Wholesale & retail | 2020 |
| Mayhill Plant Services Ltd | Construction | 2024 |
| Maynards (Holdings) Ltd | Construction | 2015 |
| Maynards Services Limited | Construction | 2019 |
| Maytech Solutions Limited | Other services | 2025 |
| Maytree Marine Limited | Real estate | 2010 |
| Mazar Transport Ltd | Transport & logistics | 2024 |
| Maze Sports Coaching Consultancy Ltd | Arts & recreation | 2015 |
| Mazur Homes Ltd | Real estate | 2026 |
| MB Green Clean Ltd | Administrative & support | 2026 |
| MB Marine Electrical Services Ltd | Construction | 2023 |
| MB Propinvest Limited | Real estate | 2012 |
| MB Solar Roofing Ltd | Construction | 2026 |
| MB Trans Ltd | Transport & logistics | 2016 |
| Mbalanda Engineering Limited | Construction | 2023 |
| MBB Consulting UK Ltd | Education | 2023 |
| Mbean Limited | Wholesale & retail | 2017 |
| MBH Plastering Ltd | Construction | 2021 |
| MBM Care Services Ltd | Health & social care | 2022 |
| Mbrampton Ltd | Manufacturing | 2020 |
| MBS Southampton Limited | Wholesale & retail | 2013 |
| Mbuchan Carpentry Limited | Construction | 2022 |
| MBX Technical Ltd | Information & communication | 2026 |
| MC Imports Ltd | Wholesale & retail | 2016 |
| MC Leicester Limited | Wholesale & retail | 2023 |
| MC London Ltd | Wholesale & retail | 2025 |
| MC Scrap Metal Recycling Ltd | Water & waste | 2026 |
| MC Shirley Limited | Wholesale & retail | 2022 |
| MC Southampton Limited | Wholesale & retail | 2022 |
| MC Trans Ltd | Transport & logistics | 2022 |
| Mc-Nic Ltd | Administrative & support | 2025 |
| MC2 Contracting Ltd | Construction | 2020 |
| MC2JS Ltd | Hospitality | 2018 |
| MCA (Southampton) Limited | Professional & scientific | 2008 |
| Mcalpine Projects Limited | Construction | 1997 |
| Mcavoy & Ross PUB Co Ltd | Hospitality | 2024 |
| MCB Prestige Transfers Limited | Transport & logistics | 2025 |
| Mcbross Ltd | Other services | 2016 |
| MCC Electrical Ltd | Construction | 2026 |
| Mcca Electrical Limited | Wholesale & retail | 2026 |
| Mccarthy Interiors Limited | Construction | 2020 |
| Mccarthy Plumbing, Heating and Renewables Limited | Construction | 2023 |
| Mccb Trading Limited | Wholesale & retail | 2019 |
| Mccormick Engineering Services Limited | Construction | 2007 |
| Mccp Limited | Information & communication | 2003 |
| Mccrone UK Limited | Professional & scientific | 2007 |
| Mcculloch Business Services Limited | Financial services | 2014 |
| Mcdonnell Brothers Property Management Limited | Construction | 1995 |
| Mcds Commercial Ltd | Construction | 2025 |
| MCF (Hampshire) LLP | | 2005 |
| MCF Group Holdings Limited | Financial services | 2020 |
| MCG Trades Ltd | Wholesale & retail | 2025 |
| Mcgillansullivan Holdings Limited | Professional & scientific | 2023 |
| Mcgovern Property Management Limited | Households | 2004 |
| Mcgovern Tech Repair Ltd | Information & communication | 2025 |
| Mcguigan Homes Limited | Extraterritorial | 2024 |
| Mcguire & Browne Plastering Ltd | Construction | 2023 |
| MCH (Southern) Ltd | Construction | 2019 |
| MCI Capital Ltd | Professional & scientific | 2022 |
| Mcintyre Mosaics Limited | Construction | 2019 |
| Mckenzie Arable Partnership LP | | 2022 |
| Mckie’S Rotational Bricks Ltd | Construction | 2022 |
| Mcknight & Davis Ltd | Households | 2016 |
| MCL Expert Delivery Ltd | Transport & logistics | 2026 |
| MCL Projects (UK) Ltd | Administrative & support | 2008 |
| Mcleonards Carpentry Limited | Construction | 2004 |
| Mcmakus Ltd | Health & social care | 2018 |
| Mcmarquer Limited | Construction | 2015 |
| Mcmillan Racing Limited | Education | 2015 |
| Mcmlxxix Enterprises Ltd | Financial services | 2025 |
| Mcoa Ltd | Wholesale & retail | 2019 |
| Mcpaint & DEC Ltd | Construction | 2022 |
| Mcphersons Building Merchants Limited | Construction | 2025 |
| MCS Realisations Limited | Administrative & support | 2012 |
| Mcsc Healthcare Limited | Wholesale & retail | 2025 |
| Mcsc Liverpool Ltd | Wholesale & retail | 2025 |
| MD Build MAX Ltd | Construction | 2025 |
| MD Ceilings Ltd | Construction | 2017 |
| MD Perfect Solution Ltd | Administrative & support | 2018 |
| MD Primeline Painting and Decorating Limited | Construction | 2026 |
| MD Roofline Ltd | Construction | 2024 |
| MD Sidhu Limited | Wholesale & retail | 2025 |
| MD Truck and Agricultural Limited | Wholesale & retail | 2021 |
| MDA Delivery Limited | Wholesale & retail | 2019 |
| MDC Building Services Ltd | Construction | 2014 |
| MDH Bodyshop Limited | Wholesale & retail | 2014 |
| MDH Care Limited | Health & social care | 2024 |
| Mdjmarine Ltd | Manufacturing | 2023 |
| MDL Commercial Services Limited | Financial services | 2013 |
| MDL Development Company Number 2 Limited | Administrative & support | 2005 |
| MDL Developments Limited | Construction | 1981 |
| MDL Estates Limited | Professional & scientific | 1979 |
| MDL Marinas Group Limited | Professional & scientific | 1985 |
| MDM Surveying Ltd | Construction | 2014 |
| Mdna Ltd | Real estate | 2010 |
| MDO Project Services Limited | Professional & scientific | 2019 |
| Mdot Digital Ltd | Wholesale & retail | 2025 |
| MDP Strategy Ltd | Professional & scientific | 2026 |
| MDR Services Group Ltd | Professional & scientific | 2025 |
| Mdrc Deli Limited | Hospitality | 2022 |