| MAT Armstrong Management LLP | | 2026 |
| MAT IT Solutions Ltd | Information & communication | 2019 |
| Matava Limited | Financial services | 2026 |
| MATCH4MARRIAGE Limited | Information & communication | 2023 |
| Matchpoint Sportz Limited | Education | 2010 |
| Matchworkers International Limited | Administrative & support | 2005 |
| Maters&Co Limited | Wholesale & retail | 2019 |
| Math Solutions Ltd | Information & communication | 2018 |
| Matharu Courier Services Ltd | Transport & logistics | 2023 |
| Mathematical Minds Tuition Limited | Education | 2021 |
| Mathon Investments Ltd | Real estate | 2024 |
| Matomale Limited | Administrative & support | 2017 |
| Matrix Education Ltd | Education | 2018 |
| Matrix Finance Ltd | Professional & scientific | 2022 |
| Matrix International (UK) Limited | Professional & scientific | 1997 |
| Matt Evans Rigging Ltd | Construction | 2013 |
| Matt James Window and Gutter Cleaning Ltd | Administrative & support | 2025 |
| Matt Mangan Fundraising Consultancy Ltd | Professional & scientific | 2025 |
| Matt Murray Limited | Information & communication | 2013 |
| Matt Wilson Coaching Limited | Education | 2024 |
| Matthew & John Homes Limited | Real estate | 2015 |
| Matthew James Hair Studio Ltd | Other services | 2019 |
| Matthewman's Sweet Peas Ltd | Wholesale & retail | 2015 |
| Matthias House Limited | Health & social care | 2018 |
| Mattison Holdings Ltd | Professional & scientific | 2019 |
| Mattress Zone Ltd | Manufacturing | 2025 |
| Mauve Create Ltd | Professional & scientific | 2020 |
| Mauve Print Management Ltd | Information & communication | 2012 |
| MAV Group Limited | Professional & scientific | 2020 |
| MAV Holding Limited | Real estate | 2021 |
| Mava Consultants Limited | Health & social care | 2014 |
| Mavam Solutions Limited | Administrative & support | 2021 |
| Maven Business Investments Ltd | Other services | 2020 |
| Mavrix Property Limited | Real estate | 2024 |
| Mawhub Foundation Ltd | Education | 2025 |
| Maxge UK Ltd | Extraterritorial | 2017 |
| Maximum Developments Limited | Real estate | 2003 |
| Maximum Projects Limited | Administrative & support | 2004 |
| Maxtil Energy Ltd | Real estate | 2023 |
| Maya Commercial Group Ltd | Wholesale & retail | 2019 |
| Mayerton Refractories (Europe) Limited | Wholesale & retail | 1998 |
| Mayerton Refractories (Ukaas) Ltd | Wholesale & retail | 2007 |
| Mayfair Court (Kingshurst) Management Company Limited | Households | 1985 |
| Mayfair Designs Limited | Wholesale & retail | 2002 |
| Mayfield Consult Limited | Real estate | 2022 |
| Mayfly Excelda Limited | Real estate | 1936 |
| Mayfly Limited | Real estate | 1956 |
| Mayfly(Corrib)Limited | Real estate | 1957 |
| Mayfly(Usk)Limited | Real estate | 1957 |
| Maypole Estates Limited | Real estate | 1994 |
| Maypole FC CIC | Arts & recreation | 2021 |
| Mayra Housing Limited | Real estate | 2020 |
| Mazahir Group Limited | Wholesale & retail | 2024 |
| Mazarine Partners Limited | Financial services | 2022 |
| Maze Worldwide Limited | Information & communication | 2023 |
| Ma’A Gené Limited | Wholesale & retail | 2025 |
| MB Express Ltd | Transport & logistics | 2023 |
| MB5 Enterprise Limited | Manufacturing | 2022 |
| Mbcjs Ltd | Other services | 2026 |
| Mbec Solutions Ltd | Information & communication | 2018 |
| Mbih Properties Limited | Real estate | 2026 |
| MBJ Gillespie Limited | Professional & scientific | 2013 |
| MBJ UK Investments Limited | Real estate | 2021 |
| MBK Consultation Services Ltd | Administrative & support | 2015 |
| Mbpharm Limited | Administrative & support | 2025 |
| Mbsm Services Ltd | Construction | 2017 |
| Mbtj Limited | Professional & scientific | 2024 |
| MC Brahma Properties Ltd | Real estate | 2024 |
| MC Courier Express Ltd | Transport & logistics | 2018 |
| MC Transportation Ltd | Transport & logistics | 2019 |
| Mcalees Consulting Limited | Other services | 2012 |
| Mccann-Erickson Central Limited | Professional & scientific | 1986 |
| Mccolgan Electrical Limited | Construction | 2006 |
| Mccormack Property Ltd | Real estate | 2022 |
| Mccoy Contractors Limited | Construction | 2017 |
| Mccracken Boxing Limited | Arts & recreation | 2018 |
| Mcdiarmid Investments Limited | Real estate | 2002 |
| Mcdonnells Ltd | Wholesale & retail | 2022 |
| Mcdowall Acquisitions Ltd | Real estate | 2021 |
| Mcdyre & Co Limited | Professional & scientific | 1988 |
| MCE Consultancy Ltd | Professional & scientific | 2015 |
| Mcferran Design Limited | Professional & scientific | 2012 |
| MCG and P&A Limited | Financial services | 2024 |
| MCG Staffing & Consultancy Ltd | Professional & scientific | 2025 |
| Mcgann & Van Limited | Transport & logistics | 2024 |
| Mcgettigan Brickwork Limited | Construction | 2012 |
| Mcgill Investments Limited | Professional & scientific | 2017 |
| Mcgill Property Limited | Real estate | 2020 |
| Mchugh Lifestyle Limited | Wholesale & retail | 1999 |
| Mchulin Ltd | Construction | 2023 |
| Mcintyre Rentables Limited | Administrative & support | 2025 |
| Mcjt Promotions Ltd | Arts & recreation | 2025 |
| Mclaren (GB) Ltd | Construction | 2014 |
| Mclaren Hire Limited | Administrative & support | 2019 |
| Mclaren Installations Limited | Construction | 2015 |
| Mcmahon Haulage Limited | Transport & logistics | 2007 |
| Mcms (UK) Limited | Professional & scientific | 2014 |
| Mcphee Investments Limited | Financial services | 2021 |
| Mcplantuk Limited | Wholesale & retail | 2020 |
| MCV Property Solutions Limited | Real estate | 2019 |