| Martello Management Limited | Professional & scientific | 2022 |
| Martin Hickley Data Solutions Limited | Administrative & support | 2014 |
| Martin James Properties Limited | Real estate | 2014 |
| Martin Mcdonald Holdings Limited | Professional & scientific | 2025 |
| Martin Moore Furniture Limited | Financial services | 2011 |
| Martin Moore Kitchens Ltd | Professional & scientific | 2013 |
| Martin Naismith Consultancy Limited | Professional & scientific | 2018 |
| Martin Oliver Bathrooms and Wetrooms Limited | Wholesale & retail | 2021 |
| Martin OUS Ltd | Real estate | 2026 |
| Martyn Allen (Radcliffe) Ltd | Wholesale & retail | 2017 |
| Martyn Allen Ltd | Health & social care | 2009 |
| Marvel Guitars Ltd | Wholesale & retail | 2014 |
| Marvin Chik Studios Limited | Professional & scientific | 2021 |
| Maryam Kauser Limited | Professional & scientific | 2015 |
| Maryam Locum Ltd | Health & social care | 2022 |
| MAS Consulting Solutions Limited | Professional & scientific | 2016 |
| Mash Sciences Limited | Professional & scientific | 2022 |
| Mashetty Estates Ltd | Real estate | 2025 |
| Mason & Shengas Properties Ltd | Real estate | 2019 |
| Mason Bidco Limited | Financial services | 2020 |
| Mason Holdco Limited | Financial services | 2020 |
| Mason Midco Limited | Financial services | 2020 |
| Mason Nominee Limited | Professional & scientific | 2020 |
| Mason Paul Estates Ltd | Real estate | 2025 |
| Mason Topco Limited | Professional & scientific | 2020 |
| Masonry Property Limited | Construction | 2022 |
| Masons Property’S (NW) Limited | Households | 2025 |
| Mass Produced Ltd | Arts & recreation | 2023 |
| Massey Design Services Ltd | Professional & scientific | 2020 |
| Master Thatchers (North) Limited | Construction | 2003 |
| Mastery Associates Ltd | Professional & scientific | 2013 |
| MAT and Reformer Fitness Ltd | Other services | 2023 |
| Match of the Dames CIC | Arts & recreation | 2025 |
| Matchbox Associates Limited | Professional & scientific | 2014 |
| Matchscene Limited | Information & communication | 1989 |
| Matf Urban Investors Ltd | Financial services | 2025 |
| Matin Consultancy Services Limited | Information & communication | 2022 |
| Matley Court Management Company Limited | Households | 2005 |
| Matrix IQ IOT Limited | Information & communication | 2023 |
| Matrix IQ Ltd | Wholesale & retail | 2002 |
| Matrix Microscience Limited | Manufacturing | 2000 |
| Matrix Pack UK Limited | Manufacturing | 2018 |
| Matrix Property Investment (Manchester 2) Limited | Extraterritorial | 2002 |
| Matrix Property Investment Limited | Extraterritorial | 2001 |
| Matrix Technologies Corporation Limited | Professional & scientific | 1998 |
| Mats Nationwide Direct Limited | Wholesale & retail | 2011 |
| Mats Nationwide Limited | Wholesale & retail | 2007 |
| Matt Davis Consulting Limited | Professional & scientific | 2023 |
| Matt Goddard FM Limited | Administrative & support | 2025 |
| Matt Smith Dentistry Ltd | Health & social care | 2022 |
| Matterform Group Ltd | Manufacturing | 2021 |
| Maude Santana Limited | Information & communication | 2019 |
| Maura Mckibbin Mediator Limited | Professional & scientific | 2016 |
| Mavens Cloud Ltd | Information & communication | 2023 |
| Mavenstone Consultants Limited | Professional & scientific | 2018 |
| Maverick & ME Ltd | Professional & scientific | 2023 |
| Maverick Marketer Limited | Administrative & support | 2017 |
| Maverick Pantry Ltd | Wholesale & retail | 2021 |
| Mavinamane Medics Ltd | Health & social care | 2021 |
| MAW Investments Limited | Real estate | 2015 |
| MAX Plant Limited | Wholesale & retail | 2002 |
| MAX Ranson Golf Limited | Arts & recreation | 2025 |
| MAX20 Holdings Limited | Financial services | 2026 |
| MAX20 Limited | Administrative & support | 2001 |
| MAX20 Project Solutions Limited | Administrative & support | 2017 |
| Maxi Motor Limited | Wholesale & retail | 2012 |
| Maxi-Check Sales Company Limited | | 1976 |
| Maxpotenti Ltd | Professional & scientific | 2014 |
| Maxx Developments Ltd | Construction | 2022 |
| Mayar Travel Limited | Administrative & support | 2015 |
| Maybridge Chemical Holdings Limited | Professional & scientific | 1997 |
| Maybridge Limited | Manufacturing | 1962 |
| Mayday Alliance Ltd | Information & communication | 2020 |
| Mayfair Real Estate Properties Ltd | Real estate | 2020 |
| Mayfair View Limited | Households | 2008 |
| Mayfield Investments Cheshire Limited | Real estate | 2020 |
| Mayfield Projects Limited | Wholesale & retail | 2015 |
| Mayfield Rosemary Avondale Limited | Professional & scientific | 2019 |
| Mayker Ltd | Professional & scientific | 2010 |
| Mayu Ltd | Health & social care | 2021 |
| Mazhax Limited | Real estate | 2026 |
| Mazilto Ltd | Information & communication | 2011 |
| MB (Lending) Limited | Financial services | 2019 |
| MB (Security Agent) Limited | Financial services | 2017 |
| MB (SUB Debt) Limited | Financial services | 2019 |
| MB (Syndicates) Limited | Financial services | 2015 |
| MB Group Holdings Ltd | Wholesale & retail | 2026 |
| MB Healthcare Advisory Limited | Professional & scientific | 2025 |
| MB Procurement Advisory Limited | Professional & scientific | 2025 |
| MB Recruitment Consulting Limited | Administrative & support | 2021 |
| MB Security Trustee Limited | Financial services | 2022 |
| MBE Altrincham Limited | Transport & logistics | 2014 |
| MBL (Business and Tax Advisers) Ltd | Professional & scientific | 2002 |
| MBM Plumbing & Heating Ltd | Construction | 2015 |
| MBM Quality Assured Limited | Professional & scientific | 2026 |
| Mbor Limited | Professional & scientific | 2018 |
| MBS Finance Limited | Financial services | 2020 |
| MBS Holdco Limited | Financial services | 2019 |
| Mbsrl Limited | Financial services | 2022 |
| Mbsv Limited | Health & social care | 2014 |