| MEN of Green Ltd | Wholesale & retail | 2021 |
| Mena Facades Ltd | Construction | 2020 |
| Mentor Realm Foundation Limited | Manufacturing | 2015 |
| Meriora Construction Ltd | Construction | 2024 |
| Merkian Limited | Administrative & support | 2025 |
| Merry and Sons Ltd | Transport & logistics | 2019 |
| Merryweather Ltd | Financial services | 2024 |
| Meryan Vans Ltd | Manufacturing | 2026 |
| Meta-Stadiums Ltd | Wholesale & retail | 2025 |
| Metameta Limited | Professional & scientific | 2016 |
| Metasphere Technologies Ltd | Information & communication | 2022 |
| Metro Real Estate Ltd | Real estate | 2024 |
| MEY Technologies Ltd | Information & communication | 2025 |
| Mfmt Ltd | Wholesale & retail | 2025 |
| MGA Chauffeurs Limited | Transport & logistics | 2025 |
| MGP Care Ltd | Health & social care | 2014 |
| MGP Scaffolding Ltd | Construction | 2019 |
| MH Transport Solutions Ltd | Administrative & support | 2025 |
| Mhcr Ltd | Wholesale & retail | 2024 |
| Mi-Inc Limited | Health & social care | 2022 |
| MIA Motors Ltd | Transport & logistics | 2023 |
| Mian Global Ltd | Wholesale & retail | 2024 |
| Michael Whitehouse Limited | Other services | 2017 |
| Michmay Limited | Health & social care | 2021 |
| Middlesex Minibus Services Ltd | Administrative & support | 2012 |
| Middx Glazing Ltd | Construction | 2021 |
| Midland Hotels Limited | Hospitality | 1981 |
| Midlands and National Ltd | Real estate | 2021 |
| MIG Trading Ltd | Wholesale & retail | 2014 |
| Migan Limited | Professional & scientific | 2015 |
| Mighty Roti Ltd | Hospitality | 2022 |
| Migrell International Co Ltd | Wholesale & retail | 2024 |
| Mihaela Ivanov Ltd | Health & social care | 2018 |
| MIJ Universe Limited | Administrative & support | 2025 |
| Mina Services Limited | Professional & scientific | 2024 |
| Minasfanisoul Limited | Health & social care | 2025 |
| Minicabwala Ltd | Transport & logistics | 2024 |
| MIR & Co Limited | Information & communication | 2013 |
| Mira Associates Limited | Professional & scientific | 2016 |
| Mirto Limited | Other services | 2017 |
| Mirza Solutions Limited | Transport & logistics | 2017 |
| Mission Foods UK Limited | Manufacturing | 1992 |
| Mister Fitter Limited | Wholesale & retail | 2015 |
| Mitashev Ltd | Construction | 2018 |
| Mitra Events UK Ltd | Administrative & support | 2025 |
| Mixingh Concrete Ltd | Manufacturing | 2021 |
| MJ Carpet & Furnitures Ltd | Wholesale & retail | 2016 |
| MJ Sahi Transport Ltd | Construction | 2025 |
| MJ Transportation Limited | Transport & logistics | 2024 |
| MJN Kitchen & Bedrooms Ltd | Manufacturing | 2018 |
| MJS Engineering Ltd | Manufacturing | 2021 |
| MK Lease Holdings Ltd | Financial services | 2023 |
| MKB Management Ltd | Real estate | 2019 |
| MLK Group Limited | Financial services | 2025 |
| MM Property Investment Ltd | Real estate | 2015 |
| MMS Decor Master Limited | Construction | 2014 |
| Moatcraft Ltd | Information & communication | 2025 |
| Mobile Mechanic West. Ltd | Wholesale & retail | 2022 |
| Mobility First Transport Ltd | Transport & logistics | 2025 |
| Moebile Services Ltd | Administrative & support | 2019 |
| Moka Digital Limited | Other services | 2020 |
| MOL Logistics (UK) Ltd. | Transport & logistics | 1988 |
| Moldfixing Ltd | Construction | 2015 |
| Moleculeo Ltd | Professional & scientific | 2025 |
| Momo Foundation | Health & social care | 2025 |
| Monk DE Luxe Limited | Professional & scientific | 2018 |
| Mono the App Ltd | Other services | 2025 |
| Monteiro Construction Limited | Construction | 2026 |
| Montous Ltd | Construction | 2019 |
| Montronix Services Ltd | Wholesale & retail | 2026 |
| Moore 4 YOU Services Ltd | Construction | 2026 |
| Mopup Services Ltd | Administrative & support | 2025 |
| Morton Close Ltd | Households | 2025 |
| Mosaica Modelling Ltd | Administrative & support | 2025 |
| Mother Mary Care Limited | Health & social care | 2022 |
| Moti Zada Investment Ltd | Real estate | 2019 |
| Motion LDN Ltd | Administrative & support | 2024 |
| Motor Lead Ltd | Wholesale & retail | 2025 |
| Motorbike Marketing Ltd | Administrative & support | 2025 |
| Mount Sierra Ltd | Health & social care | 2018 |
| Move Mountains Production Films and TV. Limited | Professional & scientific | 2020 |
| Movers & Packers Ltd | Transport & logistics | 2018 |
| MR Fresh Juice Ltd | Hospitality | 2025 |
| MR Zain Services Ltd | Administrative & support | 2018 |
| MRA Finance Limited | Professional & scientific | 2011 |
| Mriksh & Aarav Properties Ltd | Real estate | 2023 |
| MRK Prestige Bodywork Ltd | Wholesale & retail | 2026 |
| MSJ Construction Limited | Construction | 2008 |
| MSR Capital Limited | Real estate | 2025 |
| MTI Scenic Ltd | Construction | 2021 |
| MTQ Estates Private Limited | Real estate | 2017 |
| MTS 1 Limited | Transport & logistics | 2021 |
| Mubby Pizza Ltd | Hospitality | 2018 |
| Mugal Ltd | Construction | 2026 |
| Mulberry Kitchen Ltd | Hospitality | 2019 |
| Multiling Ltd | Education | 2021 |
| Mum's Dream Ltd | Wholesale & retail | 2026 |
| Mummy Yummy Ltd | Hospitality | 2022 |
| Munye Supplies Ltd | Administrative & support | 2022 |
| Muralfinder Ltd | Arts & recreation | 2024 |