| Mccarthy House Ltd | Health & social care | 2020 |
| Mccarthy SE CIC | Health & social care | 2023 |
| Mcda Solutions Ltd | Information & communication | 2021 |
| MCG Building UK Ltd | Construction | 2019 |
| MCG Cleaning UK Ltd | Administrative & support | 2023 |
| Mckenzie Mariola Properties Ltd | Real estate | 2024 |
| Mcquade Polishing Ltd | Professional & scientific | 2006 |
| MD Awan Global Ltd | Wholesale & retail | 2026 |
| MD SOL Ltd | Other services | 2024 |
| MD Spares Limited | Wholesale & retail | 2015 |
| Mddl Limited | Construction | 2017 |
| MDL Parts (UK) Limited | Wholesale & retail | 2022 |
| Mdmflow Limited | Manufacturing | 2013 |
| MDO Renovations Ltd | Construction | 2024 |
| ME2U Car Registrations Ltd | Wholesale & retail | 2022 |
| Mealdrop Ltd | Information & communication | 2026 |
| Means of Sight Ltd | Other services | 2021 |
| Meda (Millennium Enterprise Development Association) | Education | 2014 |
| Medeno Ltd | Health & social care | 2014 |
| Medical Target Ltd | Health & social care | 2014 |
| Medway Academy of Performing Arts Ltd | Arts & recreation | 2023 |
| Mega Essex Ltd | Wholesale & retail | 2022 |
| Mega Roadmap Limited | Wholesale & retail | 2022 |
| Megacr SEC Ltd | Administrative & support | 2025 |
| Megan Medicare Limited | Health & social care | 2013 |
| Megatote Limited | Information & communication | 2015 |
| Mego Foods Limited | Hospitality | 2024 |
| Mehdi and Co Limited | Professional & scientific | 2012 |
| Mehrok Construction Ltd | Construction | 2020 |
| Mejia Wind Services Ltd | Manufacturing | 2023 |
| Mela Property Ltd | Hospitality | 2026 |
| Melan Beauty Organic Limited | Manufacturing | 2021 |
| Memora House Ltd | Information & communication | 2026 |
| Memz Limited | Hospitality | 2023 |
| Mesh-Net Ltd | Information & communication | 2010 |
| Metafobs UK Limited | Hospitality | 2022 |
| Mezo Services (UK) Ltd | Transport & logistics | 2019 |
| MFZ Trading & Services Limited | Wholesale & retail | 2025 |
| MG Lifting Project Ltd | Construction | 2018 |
| MGP Consult Limited | Professional & scientific | 2013 |
| MGR Fresh Produce Limited | Wholesale & retail | 2022 |
| MGR Merchants Ltd | Real estate | 2024 |
| MH Car Services Ltd | Transport & logistics | 2018 |
| MHS Coms Properties Ltd | Real estate | 2023 |
| MI EAR Clinic Limited | Health & social care | 2025 |
| Michael Gregg Consultancy Ltd | Other services | 2004 |
| Michael Morris Accountancy Services Limited | Professional & scientific | 2005 |
| Michael Properties London Ltd | Real estate | 2023 |
| Mickky and Sons Auto Tech Ltd | Wholesale & retail | 2020 |
| Midnight Surprise Ltd | Hospitality | 2020 |
| MIE Care Service Limited | Health & social care | 2016 |
| Miers Court Estates Limited | Real estate | 1972 |
| Mies Financial Ltd | Professional & scientific | 2025 |
| Miha&Alexhouse Ltd | Hospitality | 2026 |
| Mihai B Ltd | Transport & logistics | 2019 |
| Mihai Trans Ltd | Transport & logistics | 2015 |
| Mihail Drylining Ltd | Financial services | 2019 |
| Mikaelwest Limited | Transport & logistics | 2016 |
| Mikani Properties Limited | Real estate | 2018 |
| Mikelil & Co Ltd | Health & social care | 2024 |
| Mikestraderepair Ltd | Other services | 2025 |
| Miklas Building Limited | Construction | 2018 |
| Milionaire Limited | Wholesale & retail | 2025 |
| Milkage Ltd | Professional & scientific | 2021 |
| Millennium Audio Distribution Limited | Manufacturing | 1999 |
| Millennium Plumbing & Heating Ltd | Construction | 2018 |
| Millie Beauty Ltd | Other services | 2024 |
| Milpatex Limited | Health & social care | 2023 |
| Mimosa Lettings Ltd | Hospitality | 2019 |
| Mimu Property Services Limited | Households | 2025 |
| Mimu Technical Services Ltd | Construction | 2026 |
| Mind Art 2020 Ltd | Wholesale & retail | 2020 |
| Mindcare Limited | Real estate | 2022 |
| Mirdita Building Services Ltd | Construction | 2019 |
| Miri Piri Samagam C.I.C. | Health & social care | 2025 |
| Miriam and Luke Limited | Hospitality | 2025 |
| Mirsnamo Limited | Professional & scientific | 2015 |
| Misima Services Ltd | Hospitality | 2022 |
| Mitech Shine Ltd | Wholesale & retail | 2014 |
| MK9 Investments Ltd | Real estate | 2020 |
| MKA Care Limited | Health & social care | 2021 |
| MKH Property Development (UK) Ltd | Construction | 2023 |
| Mksquare Ltd | Water & waste | 2021 |
| ML Rail Solutions Limited | Construction | 2022 |
| Mline (Essex) Ltd | Wholesale & retail | 2026 |
| Mllec Holdings Ltd | Financial services | 2018 |
| MLT RO Limited | Transport & logistics | 2022 |
| MM Dent Plus Ltd | Health & social care | 2025 |
| Mm-Healthcare Limited | Health & social care | 2026 |
| MMC Mechanical Ltd | Construction | 2020 |
| MMD Construction Ltd | Construction | 2025 |
| MMM Security Ltd | Administrative & support | 2024 |
| Mmmjd Ltd | Professional & scientific | 2011 |
| MNA Homes Limited | Real estate | 2023 |
| MNE Cuts Limited | Other services | 2026 |
| MNJ Transport Ltd | Transport & logistics | 2025 |
| Mnjr Services Ltd | Transport & logistics | 2023 |
| MNY Glassware Limited | Wholesale & retail | 2023 |
| Moda UK Properties Ltd | Real estate | 2025 |
| Modern Rendering Limited | Construction | 2014 |