| Mur-Mur Limited | Transport & logistics | 2015 |
| Murray Construction & Development Limited | Wholesale & retail | 2002 |
| Murray Hogg Limited | Transport & logistics | 1974 |
| Murs Consultancy Services Ltd | Professional & scientific | 2020 |
| Musab Bilal Limited | Wholesale & retail | 2023 |
| Musafa Ltd | Information & communication | 2024 |
| Musar Property Group Ltd | Real estate | 2025 |
| Musariri Limited | Health & social care | 2014 |
| Musayah Limited | Real estate | 2026 |
| Musculoskeletal Partners Network Limited | Health & social care | 2018 |
| Musfits Inc. Community Interest Company | Health & social care | 2025 |
| Mushroom Works Community Interest Company | Real estate | 2006 |
| Music in Music OUT Publishing Limited | Information & communication | 2025 |
| Music Network UK Ltd. | Other services | 2016 |
| Music Sphere Ltd | Arts & recreation | 2023 |
| Musical Buds CIC | Education | 2021 |
| Musson Brown Architects Ltd | Professional & scientific | 2020 |
| Musson Medicine Ltd | Education | 2025 |
| Must Have Collectibles Ltd | Wholesale & retail | 2019 |
| Mustaciosu Logistics Limited | Transport & logistics | 2025 |
| Mustafa Medical Ltd | Health & social care | 2023 |
| Mustique Limited | Financial services | 2021 |
| Mutha Cuva Limited | Other services | 2023 |
| Mutji Limited | Health & social care | 2022 |
| Mutos Ltd | Hospitality | 2019 |
| Mutts 'N Moggies Motel Limited | Administrative & support | 2009 |
| Mutualshare Property Management Limited | Households | 1991 |
| MUX Express Ltd | Wholesale & retail | 2026 |
| MUX United Ltd | Wholesale & retail | 2024 |
| Muxworthy Property Solutions Limited | Professional & scientific | 2013 |
| MVH Rental Ltd | Administrative & support | 2018 |
| MVP Club Limited | Professional & scientific | 2018 |
| MVP Wednesdays UK Ltd | Professional & scientific | 2022 |
| MW Broadcast Services Ltd | Information & communication | 2024 |
| MW Coaching Ltd | Education | 2026 |
| MW Plumbing & Heating Contractors Ltd | Construction | 2013 |
| MWG Limited | Real estate | 2017 |
| MWH Leisure Limited | Hospitality | 2021 |
| MWI Medical Limited | Health & social care | 2025 |
| MWK PUB Ltd | Hospitality | 2023 |
| MWM Consultancy Leasing Ltd | Hospitality | 2023 |
| MWM Consultancy Property Ltd | Hospitality | 2026 |
| MWT Waste Ltd | Water & waste | 2020 |
| MX1 Limited | Wholesale & retail | 2021 |
| MX1 Propco Ltd | Real estate | 2025 |
| MXA Ltd | Extraterritorial | 2014 |
| My Aesthetic Lounge Limited | Health & social care | 2024 |
| My Car Cleaning Distribution Ltd | Wholesale & retail | 2021 |
| My Car Cleaning Ltd | Wholesale & retail | 2018 |
| My Car Plates Ltd | Wholesale & retail | 2020 |
| My Coastal Escapes Limited | Hospitality | 2022 |
| My Delhi Streetery Limited | Hospitality | 2019 |
| My DHD Ltd | Information & communication | 2017 |
| My Dream Sofa Ltd | Wholesale & retail | 2024 |
| My Family Matters Limited | Financial services | 2017 |
| My Food Stories Limited | Wholesale & retail | 2021 |
| My Foster Carer Ltd | Health & social care | 2024 |
| My Greek Tutor Ltd | Education | 2023 |
| My Healthcare Recruit Ltd | Administrative & support | 2017 |
| My Kiki Ltd. | Wholesale & retail | 2014 |
| My Little Toy Boxes Limited | Manufacturing | 2024 |
| My Mentors Global Ltd | Other services | 2025 |
| My Merchants Market Ltd | Professional & scientific | 2026 |
| My Mobile Barber Ltd | Other services | 2021 |
| My New Future CIC | Information & communication | 2025 |
| My Own Home Limited | Real estate | 2024 |
| My Study Bridge Ltd | Education | 2012 |
| My Top Brands Ltd | Wholesale & retail | 2021 |
| My Tour Finders Ltd | Administrative & support | 2025 |
| My Transport Planner Limited | Information & communication | 2018 |
| My TSE Investments Limited | Real estate | 2020 |
| My Versatile Healthcare Ltd | Administrative & support | 2018 |
| My Will My Choice Limited | Professional & scientific | 2016 |
| MY9 Testimonial Ltd | Other services | 2025 |
| MYC Clothing Limited | Wholesale & retail | 2025 |
| Myden Properties Limited | Hospitality | 2021 |
| Myers and SON Limited | Real estate | 2024 |
| Myfd Ltd | Professional & scientific | 2025 |
| Myheartcare Limited | Health & social care | 2016 |
| Myhouse-Ne Limited | Real estate | 2016 |
| Myindusworld Limited | Wholesale & retail | 2024 |
| Myka Group Ltd | Hospitality | 2018 |
| Myles Commercial Ltd | Financial services | 2025 |
| Myles Mortgages Ltd | Financial services | 2020 |
| Myles Properties (NE) Ltd | Real estate | 2022 |
| Mylets Newcastle Ltd | Real estate | 2019 |
| MYN Trans & Services Ltd | Construction | 2025 |
| Myplace Cleans Ltd | Administrative & support | 2026 |
| Myprofessionalpassport Ltd | Information & communication | 2019 |
| Myriad Electrical Contractors Ltd | Construction | 2022 |
| Myrtle Medical Services Limited | Health & social care | 2015 |
| Mysky Investment Limited | Real estate | 2024 |
| Mystic FOX Ltd | Professional & scientific | 2024 |
| Myth Drinks Ltd | Manufacturing | 2016 |
| Mythic Margins Ltd | Manufacturing | 2025 |
| Myusacandy Limited | Wholesale & retail | 2022 |
| MYV Services Limited | Health & social care | 2023 |
| MZ Innovations Limited | Real estate | 2024 |
| MZM Diamond Shine Ltd | Other services | 2021 |
| N & D London Investments | Administrative & support | 2003 |