| Mason Wild Services Limited | Manufacturing | 2017 |
| Masons Plumbing & Heating Contractors Ltd | Construction | 2019 |
| Masraf Capital International JP Ltd | Financial services | 2024 |
| Mass Distribution Limited | Wholesale & retail | 2003 |
| Mass-One Spedition Ltd | Transport & logistics | 2021 |
| Massage Thai Medical Therapy UK Ltd | Health & social care | 2021 |
| Massk Property Investment Ltd | Real estate | 2021 |
| Mast Digital (UK) Ltd | Wholesale & retail | 2014 |
| Master Dough Ltd | Hospitality | 2024 |
| Master Fade Barber Shop Limited | Other services | 2023 |
| Master Tailor Doncaster Ltd | Manufacturing | 2020 |
| Master Your Performance Ltd | Professional & scientific | 2023 |
| Masterbrand Global Ltd | Wholesale & retail | 2026 |
| Masterchef Bawtry Limited | Hospitality | 2008 |
| Mastersave Limited | Extraterritorial | 2012 |
| MAT & Mouse IT Services Limited | Information & communication | 2009 |
| MAT Trans Ltd | Transport & logistics | 2024 |
| Matarova Property Management Ltd | Real estate | 2025 |
| Matas Andriekus Ltd | Transport & logistics | 2020 |
| Matek Ltd | Transport & logistics | 2024 |
| Mater DEI Limited | Real estate | 2022 |
| Mateusz Wasiolek Ltd | Transport & logistics | 2014 |
| Mathias Express Ltd | Construction | 2026 |
| Maths Healthcare Limited | Transport & logistics | 2016 |
| Matia Transport Ltd | Transport & logistics | 2025 |
| Matlyn Homes Limited | Construction | 2022 |
| Matn Limited | Health & social care | 2021 |
| Matrix SP Ltd | Transport & logistics | 2012 |
| Matt G Illustration Ltd | Professional & scientific | 2026 |
| Matt Golbourn Transport Limited | Transport & logistics | 2021 |
| Matt Roberts Builders Limited | Construction | 2014 |
| Mattazon Ltd | Transport & logistics | 2020 |
| Mattella Drivers Ltd | Transport & logistics | 2018 |
| Matter Creative Limited | Professional & scientific | 2020 |
| Mattercap UK Ltd | Financial services | 2023 |
| Matthew Acton Ltd | Administrative & support | 2011 |
| Matthew Appleyard Developments Limited | Construction | 2015 |
| Matthew Hare Investments Limited | Real estate | 2012 |
| Matthew James Kirk Limited | Real estate | 2018 |
| Matthew KAY Interiors Limited | Construction | 2020 |
| Matthew Paul Limited | Wholesale & retail | 2025 |
| Matthew Scholes Productions Ltd | Professional & scientific | 2011 |
| Matthewemson Ltd | Administrative & support | 2018 |
| Matthouse Ltd | Real estate | 2026 |
| Matun Enterprise Limited | Construction | 2024 |
| Mauby Limited | Real estate | 2024 |
| Mauings Limited | Professional & scientific | 2013 |
| Maus Mould Services Limited | Manufacturing | 2002 |
| MAV Healthcare Ltd | Wholesale & retail | 2020 |
| Mave Speed Ltd | Wholesale & retail | 2026 |
| Maverick Project Management Ltd | Information & communication | 2012 |
| Mavn Solutions Ltd | Construction | 2018 |
| MAW Lettings Ltd | Real estate | 2024 |
| Mawonet Ltd | Professional & scientific | 2023 |
| Mawsons Property Vision Ltd | Real estate | 2025 |
| MAX & DOM Ltd | Real estate | 2026 |
| MAX Design Consultancy Ltd | Professional & scientific | 2010 |
| MAX Engineering Limited | Manufacturing | 2006 |
| MAX Farmer Plastering Limited | Construction | 2006 |
| MAX Supplements Ltd | Wholesale & retail | 2021 |
| MAX Victory Consulting Ltd | Information & communication | 2004 |
| Maxand Ltd. | Transport & logistics | 2019 |
| Maxeydent Limited | Administrative & support | 2003 |
| Maxi Hughes Ltd | Arts & recreation | 2022 |
| Maxi Suplement Ltd | Wholesale & retail | 2025 |
| Maximus Minerals Ltd | Financial services | 2022 |
| Maxton Investments Limited | Financial services | 2021 |
| MAY Blossom Property Ltd | Real estate | 2026 |
| MAY Investco Limited | Real estate | 2021 |
| Maya Food and Drink Limited | Wholesale & retail | 2026 |
| Maya Rail Technical Training & Consultancy Ltd | Education | 2015 |
| Maya Technology Ltd | Information & communication | 2019 |
| Mayfair Meridian Group Ltd | Wholesale & retail | 2025 |
| Mayfair Walls Ltd | Construction | 2026 |
| Mayflower Management Limited | Professional & scientific | 2016 |
| Mayflower Sanctuary Boarding Limited | Other services | 2023 |
| Mayil Investment Ltd | Real estate | 2024 |
| MB Administration Ltd | Professional & scientific | 2021 |
| MB Cards Ltd | Wholesale & retail | 2024 |
| MB Case Management Ltd | Health & social care | 2026 |
| MB Competitions Ltd | Wholesale & retail | 2020 |
| MB Creative Property Investments Ltd | Real estate | 2022 |
| MB Direct Properties Ltd | Real estate | 2019 |
| MB Drones Ltd | Information & communication | 2017 |
| MB Edition Ltd | Information & communication | 2020 |
| MB Gaming Centre Ltd | Wholesale & retail | 2020 |
| MB Garden Services Limited | Administrative & support | 2015 |
| MB Gardening Ltd | Administrative & support | 2020 |
| MB Grading Ltd | Administrative & support | 2026 |
| MB Hydropool Ltd | Arts & recreation | 2019 |
| MB Mechanics Limited | Wholesale & retail | 2025 |
| MB Physio Ltd | Health & social care | 2022 |
| MB Rehab Ltd | Health & social care | 2022 |
| MB Residential Ltd | Real estate | 2022 |
| MB Scooters Ltd | Manufacturing | 2011 |
| MB Tools Limited | Wholesale & retail | 2025 |
| MB UK Medicals Limited | Other services | 2026 |
| MBG Electrical Limited | Construction | 2017 |
| MBI Transports Ltd | Transport & logistics | 2020 |
| MBP Developments Ltd | Real estate | 2011 |