| Mestan Properties Limited | Real estate | 2024 |
| Mestra Software Limited | Information & communication | 2012 |
| Met&Connect Ltd | Professional & scientific | 2023 |
| MET145 Ltd | Hospitality | 2024 |
| Meta Q2 Limited | Information & communication | 2022 |
| Metaal Compagnie Ltd | Wholesale & retail | 2025 |
| Metal Products (Doncaster) Limited | Manufacturing | 2004 |
| Metallgutten Hosting Limited | Professional & scientific | 2011 |
| Metis First Limited | Financial services | 2015 |
| Metres to Miles Limited | Wholesale & retail | 2008 |
| Metroland Limited | Construction | 2000 |
| Metroline Mobility Ltd | Extraterritorial | 2025 |
| Metrospark Services Ltd | Administrative & support | 2025 |
| Mettech Fabrications Ltd | Manufacturing | 2014 |
| Mettech Holdings Limited | Manufacturing | 2019 |
| Metzuda Ltd | Administrative & support | 2024 |
| Mexborough Investments Ltd | Real estate | 2004 |
| Mexichem Dura-Line UK, Ltd | Manufacturing | 2015 |
| Mexichem Wavin UK Ltd | Manufacturing | 2015 |
| Meyco Fresh UK Ltd | Wholesale & retail | 2025 |
| Meyr Ltd | Professional & scientific | 2016 |
| Meysam Stop & Shop Ltd | Wholesale & retail | 2021 |
| Mezzanet Limited | Construction | 2020 |
| MF Agri Promotions Ltd | Wholesale & retail | 2025 |
| MF Cladding Ltd | Construction | 2022 |
| MF Consultancy (Bawtry) Ltd | Professional & scientific | 2020 |
| MF Industrial Developments Limited | Wholesale & retail | 2022 |
| MG Dentix LLP | | 2021 |
| MG Group Ltd | Construction | 2025 |
| MG International Trade Services Limited | Wholesale & retail | 2010 |
| MG Prestige Antiques Limited | Wholesale & retail | 2025 |
| MG Properties Nottingham Limited | Real estate | 2026 |
| MG Sports and Racing Ltd | Manufacturing | 2023 |
| MG Supply Chain Services Ltd | Professional & scientific | 2021 |
| MG73 Ltd | Transport & logistics | 2014 |
| MGB Care Services Limited | Health & social care | 2000 |
| Mgbr Properties Limited | Real estate | 2025 |
| MGH Burners Ltd | Wholesale & retail | 2014 |
| MGH Developments Limited | Construction | 2020 |
| MGH Recycling Limited | Other services | 1993 |
| MGM 22 Driver Ltd | Transport & logistics | 2020 |
| MGM Freight Limited | Transport & logistics | 2025 |
| MGM Pharm Ltd | Health & social care | 2017 |
| MGR4LOGISTIC Ltd | Transport & logistics | 2016 |
| Mgvdv Ltd | Professional & scientific | 2025 |
| Mgyd Ltd | Transport & logistics | 2018 |
| MH Booth Ltd | Administrative & support | 2023 |
| MH Celler Ltd | Wholesale & retail | 2023 |
| MH Talent Ltd | Administrative & support | 2024 |
| MH TM Ltd | Public administration | 2024 |
| MH101 Limited | Construction | 2023 |
| MHA Property Group Holdings Limited | Financial services | 2025 |
| Mhbp Developments Ltd | Construction | 2019 |
| Mhbp Holdings Ltd | Real estate | 2024 |
| Mhbp Properties Ltd | Real estate | 2021 |
| MHG Transporter Ltd | Transport & logistics | 2020 |
| Mi-How Limited | Transport & logistics | 2025 |
| MI2FF Ltd | Construction | 2016 |
| MI82TRANS Limited | Transport & logistics | 2017 |
| MIA Gibbs Limited | Arts & recreation | 2019 |
| MIA Maid Cleaning Limited | Administrative & support | 2025 |
| Miami Tanning Worksop Limited | Other services | 2023 |
| MIC Brands Ltd | Wholesale & retail | 2026 |
| MIC Management Ltd | Real estate | 2021 |
| Mica Mini Market Ltd | Wholesale & retail | 2024 |
| Mica Romani Limited | Wholesale & retail | 2023 |
| Mica-Suca Ltd | Hospitality | 2021 |
| Michael Baroo Ltd | Transport & logistics | 2019 |
| Michael D Wood Limited | Manufacturing | 2014 |
| Michael Finley and Associates Ltd | Professional & scientific | 2024 |
| Michael MEE Holdings Ltd | Financial services | 2022 |
| Michael MEE Limited | Construction | 2017 |
| Michael Murphy & Limited | Administrative & support | 2012 |
| Michael Poulter Decorators Limited | Construction | 2019 |
| Michael Rodwell Repatriation Ltd | Other services | 2015 |
| Michael Shanahan Travel Ltd | Administrative & support | 2019 |
| Michael Smith TM Ltd | Other services | 2019 |
| Michael Suszwalak Ltd | Administrative & support | 2026 |
| Michaels Mews (Aylesbury) Management Company Limited | Households | 2003 |
| Michal Korthals Ltd | Wholesale & retail | 2013 |
| Michal Stepniak Ltd | Manufacturing | 2018 |
| Michelle Brookes Training Academy (Brillbird North East) Ltd | Wholesale & retail | 2018 |
| Micio Trans Ltd | Transport & logistics | 2017 |
| Mick Chambers Construction Limited | Construction | 2023 |
| Mick Cooper Arboricultural Consultants Ltd | Agriculture & fishing | 2015 |
| Mick Pittaway TM Ltd | Public administration | 2025 |
| Mick's Beds Limited | Wholesale & retail | 2015 |
| Mickarrell Properties Limited | Real estate | 2025 |
| Micro Alarms Fire and Security Limited | Professional & scientific | 2008 |
| Micro Alarms Limited | Administrative & support | 1995 |
| Micro Brew UK Limited | Manufacturing | 2016 |
| Micro Medics Limited | Health & social care | 2022 |
| Microcare Service Limited | Health & social care | 2025 |
| Microx Europe Ltd | Wholesale & retail | 2016 |
| Midak LLP | | 2004 |
| Midas Jewellery Design Limited | Manufacturing | 2019 |
| Midas MOT & Repair Centre Limited | Wholesale & retail | 2016 |
| Midas Underwriting Ltd | Financial services | 2000 |
| Middle Eastern Grill Ltd | Hospitality | 2025 |
| Middlehurst TM Ltd | Construction | 2024 |