| MIY Group Limited | Administrative & support | 2021 |
| MIY Yacht Ltd | Wholesale & retail | 2021 |
| MJ Aviation Services Ltd | Professional & scientific | 2022 |
| MJ Electrical Installations Ltd | Construction | 2022 |
| MJ Solar Installations Ltd | Construction | 2022 |
| MJD Ventures Limited | Information & communication | 2015 |
| Mjdl Limited | Real estate | 2023 |
| MJG Limited | Professional & scientific | 2024 |
| MJK Capital Group Ltd | Real estate | 2025 |
| Mjootle Ltd | Information & communication | 2018 |
| MJT Electrical (Coventry) Ltd | Construction | 2024 |
| MK Howard Consultancy Limited | Administrative & support | 2015 |
| Mkvli Ltd | Wholesale & retail | 2024 |
| Mleansolutions Limited | Professional & scientific | 2022 |
| Mlib Limited | Health & social care | 2022 |
| MLK Property Lettings Limited | Administrative & support | 2022 |
| MM Express Ltd | Transport & logistics | 2020 |
| Mmdh Properties Ltd | Real estate | 2025 |
| MN North Construction Ltd | Construction | 2011 |
| Modap's Wigs Ltd | Other services | 2018 |
| Modern Social Ltd | Financial services | 2025 |
| Mojo Alliance Ltd | Extraterritorial | 2006 |
| Mojoe Community Ltd | Information & communication | 2024 |
| Moke International Limited | Manufacturing | 2015 |
| Molben Investments Holdings Limited | Financial services | 2021 |
| Momentum Performance Consulting Limited | Professional & scientific | 2024 |
| Momo Lisa Ltd | Hospitality | 2024 |
| Monark Butterflye Ltd | Wholesale & retail | 2025 |
| Monsoon Estates Limited | Wholesale & retail | 2020 |
| Montanaro Associates Limited | Professional & scientific | 1993 |
| Moon Chimp Limited | Extraterritorial | 2017 |
| Moon Industries Ltd | Manufacturing | 2021 |
| Moonshot Series Limited | Education | 2022 |
| Moonstorm Media Limited | Information & communication | 2010 |
| Moremortgages Ltd | Financial services | 2020 |
| Morgan Geotechnics Limited | Construction | 2017 |
| Morgan Holdings (Midlands) Limited | Administrative & support | 2021 |
| Morgan Swiss Estates Ltd | Real estate | 2022 |
| Morgan Swiss Limited | Other services | 2018 |
| Moriato Limited | Information & communication | 2018 |
| Mormag Asset Management Limited | Professional & scientific | 2025 |
| Morris Properties Warwickshire Limited | Construction | 2025 |
| Morrow Holdings Limited | Financial services | 2021 |
| Morton House Management Limited | Real estate | 2017 |
| Moserve (Rugby) Limited | Wholesale & retail | 2007 |
| Motabars Limited | Wholesale & retail | 2018 |
| Mother Ocean Blue Limited | Education | 2020 |
| Motif Tile and Stone Ltd | Construction | 2023 |
| Motivational Business Network Ltd | Information & communication | 2026 |
| Motor Car Centre Limited | Wholesale & retail | 2002 |
| Motor Cycle World L\Spa Limited | Wholesale & retail | 2001 |
| Motorsport Ltd | Other services | 2017 |
| Motum UK Limited | Other services | 2019 |
| Moulton Carpentry Ltd | Manufacturing | 2020 |
| Mountain Pictures Limited | Information & communication | 2019 |
| MOV Logistics Ltd | Construction | 2018 |
| Move IT Shake IT Events Limited | Education | 2022 |
| Move IT Shake IT International Limited | Education | 2024 |
| Move IT Shake IT Ltd | Education | 2021 |
| Move Well Clinics Ltd | Health & social care | 2026 |
| Movement Positive Limited | Professional & scientific | 2017 |
| Moving Frame Studios Limited | Information & communication | 2026 |
| Mowbray Marketing Ltd | Other services | 2019 |
| MP Autos Ltd | Wholesale & retail | 2021 |
| MP Projects Ltd | Construction | 2024 |
| MP Self Storage Limited | Transport & logistics | 2025 |
| MP53 Limited | Professional & scientific | 2025 |
| Mpcs Property Ltd | Real estate | 2023 |
| MPM Haulage Limited | Transport & logistics | 2016 |
| MPM Trans Limited | Transport & logistics | 2026 |
| MR AAA GAS Ltd | Construction | 2025 |
| MR Capital Global Ltd | Wholesale & retail | 2022 |
| MR Investigations Ltd | Administrative & support | 2019 |
| MR Mark Frolo Ltd | Information & communication | 2012 |
| Mrhb Ltd | Health & social care | 2023 |
| MRK Components Limited | Wholesale & retail | 2022 |
| MRM Elec Ltd | Construction | 2026 |
| MRR Property Ltd | Real estate | 2025 |
| MS Professional Management Ltd | Construction | 2014 |
| Msave Designs Ltd | Professional & scientific | 2022 |
| Msjw Consult Ltd | Construction | 2022 |
| Mspsl Instructor & Driver Training Ltd | Education | 2024 |
| MSR Phone Zone Ltd | Wholesale & retail | 2026 |
| MSZ International Consulting Ltd | Real estate | 2019 |
| MSZ Investments 2 (DDL) Limited | Real estate | 2021 |
| MSZ Investments 2 Limited | Real estate | 2020 |
| MSZ Investments Limited | Real estate | 2017 |
| Mugford Training Limited | Professional & scientific | 2016 |
| Mulberry Cleaning Company Limited | Administrative & support | 2022 |
| Mulberry Facilities Maintenance Limited | Agriculture & fishing | 2021 |
| Mullaney and Co Limited | Transport & logistics | 2019 |
| Multi Utility Service Provider Ltd | Other services | 2018 |
| Multilink Resources Limited | Wholesale & retail | 1996 |
| Mundy Van Security Ltd | Manufacturing | 2020 |
| Munny Limited | Administrative & support | 2018 |
| Munqui Limited | Information & communication | 2016 |
| Muntjac Property Ltd | Construction | 2019 |
| Murat Olives Ltd | Hospitality | 2026 |
| Murray Brother's Whisky Ltd | Wholesale & retail | 2014 |
| Musical Nutrition Ltd | Information & communication | 2023 |