| Mbiit Ltd. | Information & communication | 2014 |
| Mboka Connect Ltd | Education | 2025 |
| MBS Chef Ltd | Hospitality | 2025 |
| MBS Medical Systems Ltd | Health & social care | 2021 |
| MBS Securities Limited | Administrative & support | 2020 |
| MC Construction & Electrical Contractors Limited | Construction | 2011 |
| MC GAS & Plumbing 24/7 Limited | Construction | 2019 |
| MC Green Advisory Ltd | Professional & scientific | 2025 |
| MC Haylom General Building Ltd | Construction | 2025 |
| MC Legal Services Limited | Professional & scientific | 2020 |
| MC Plumbing London Ltd | Construction | 2026 |
| MCA Training and Support Solutions Ltd | Education | 2025 |
| Mcadam Drive Flats Management Limited | Households | 1977 |
| Mcarthur Morgan Limited | Education | 2009 |
| Mcbd Properties Ltd | Real estate | 2019 |
| MCD Courier Limited | Transport & logistics | 2024 |
| MCD Property Ltd | Real estate | 2015 |
| Mcdermott Care Group Limited | Professional & scientific | 2025 |
| Mcewan Construction Limited | Construction | 2020 |
| MCG Management Consultancy Ltd | Construction | 2024 |
| Mcgloin Holdings Limited | Real estate | 2021 |
| Mcgloin Properties Ltd | Real estate | 2020 |
| Mcloughlin Decorating Limited | Construction | 1995 |
| MCM Property Maintenance Ltd | Construction | 2021 |
| Mcmd Ltd | Transport & logistics | 2026 |
| MCO Consulting and Marketing Limited | Professional & scientific | 2020 |
| MCO Prestige UK Limited | Transport & logistics | 2018 |
| Mcpear Security Services Ltd | Administrative & support | 2011 |
| MD Building & Construction Ltd | Construction | 2020 |
| MD Contractors Ltd | Construction | 2021 |
| MD Dental Services (Laboratory) Ltd | Health & social care | 2015 |
| Mdad Consultancy Ltd | Professional & scientific | 2023 |
| Mdfa Investments Ltd | Real estate | 2025 |
| MDH & EIA Property Investments Limited | Real estate | 2024 |
| MDH & JH Property Investments Limited | Real estate | 2024 |
| MDH UK Property Investments Limited | Real estate | 2023 |
| MDM and JTM Ltd | Real estate | 2020 |
| MDS Battery Limited | Manufacturing | 1989 |
| ME Invest LDN Ltd | Real estate | 2026 |
| ME Properties Investment Ltd | Real estate | 2022 |
| Meadowfield Homes Limited | Real estate | 2021 |
| Meat Express Ltd | Wholesale & retail | 2023 |
| Mechanical Digger Ltd | Households | 2023 |
| Mecnun Deniz Trading Ltd | Wholesale & retail | 2020 |
| Medcalf Road (Freehold) Limited | Administrative & support | 2001 |
| MEDDUSAGOLD4 Ltd | Manufacturing | 2023 |
| Medi & Sons Wholesale Ltd | Wholesale & retail | 2025 |
| MEDI2GO Ltd | Hospitality | 2024 |
| Media Xchange Group Limited | Wholesale & retail | 2015 |
| Mediaport Systems Ltd | Manufacturing | 2023 |
| Medical for Life Limited | Health & social care | 2009 |
| Medicus Health Partners Ltd | Health & social care | 2019 |
| Mediguide Ltd | Administrative & support | 2021 |
| Medino Limited | Health & social care | 2015 |
| Medish Limited | Wholesale & retail | 2024 |
| Medispa Guide Ltd | Wholesale & retail | 2022 |
| Medisrealbbq Ltd | Hospitality | 2025 |
| Mediu & Partners Estates Limited | Real estate | 2025 |
| Mediwave Clinic Limited | Health & social care | 2025 |
| Mediyah Ltd | Information & communication | 2018 |
| Medlar Lockhart Limited | Real estate | 2014 |
| Medsag Limited | Professional & scientific | 2025 |
| Medtech Lasers Ltd | Administrative & support | 2019 |
| Medtick Limited | Health & social care | 2012 |
| Medulla Labs Limited | Other services | 2019 |
| Medusa Assets Ltd | Real estate | 2026 |
| Medway Estates Limited | Real estate | 2020 |
| Medway Heating & Plumbing Ltd | Construction | 2024 |
| Medwell Properties Ltd | Real estate | 2021 |
| Mega Bargains Limited | Wholesale & retail | 2025 |
| Mega Care Limited | Health & social care | 2026 |
| Mega Care Plus Limited | Health & social care | 2018 |
| Mega Foods UK Limited | Wholesale & retail | 2017 |
| Mega Grill Ltd | Hospitality | 2025 |
| Megacutz Unisex Salon Limited | Other services | 2019 |
| Megaled Limited | Manufacturing | 2007 |
| Meganova Investments Limited | Real estate | 2017 |
| Megsnanny Ltd | Health & social care | 2021 |
| Mehdiward UK LLP | | 2018 |
| Mehir Restaurant Limited | Hospitality | 2019 |
| Mehmet Properties Ltd | Real estate | 2019 |
| Meinc Solutions Limited | Education | 2014 |
| Meirow Diamonds London Limited | Wholesale & retail | 2015 |
| Meiyo Solutions Limited | Information & communication | 2022 |
| Meka Electrical Ltd | Construction | 2024 |
| Meka Trading Ltd | Wholesale & retail | 2018 |
| Mekik Ltd | Other services | 2021 |
| Meks Garden Machinery Ltd | Manufacturing | 2022 |
| MEL & BEL Packaging and Logistics Ltd | Other services | 2008 |
| MEL Makeup Ltd | Other services | 2025 |
| Melach Consulting Limited | Professional & scientific | 2020 |
| Melding Ltd | Administrative & support | 2013 |
| Melian Traders Limited | Wholesale & retail | 2026 |
| Melibre Limited | Wholesale & retail | 2023 |
| Melina Properties Ltd | Real estate | 2024 |
| Melisa Fish & Chips Limited | Hospitality | 2026 |
| Melissa Decorate Ltd | Construction | 2018 |
| Mellitrade Ltd | Wholesale & retail | 2022 |
| Melr Hair Ltd | Other services | 2024 |
| Melsglowhouse Limited | Other services | 2021 |