| Mart More Limited | Wholesale & retail | 2024 |
| Martin & Phelps Properties Limited | Real estate | 2021 |
| Martin & SON Holdings Ltd | Real estate | 2023 |
| Martin Burge & Co Limited | Manufacturing | 2018 |
| Martin Clack Motor Engineering Limited | Wholesale & retail | 2026 |
| Martin Feighery Brickwork Ltd | Construction | 2022 |
| Martin Kelly Cleaning Services Ltd | Administrative & support | 2013 |
| Martin Kelly Commercial Cleaning Ltd | Administrative & support | 2015 |
| Martin Powell Engineering Limited | Manufacturing | 2008 |
| Martin Robson Limited | Professional & scientific | 2004 |
| Martin-Luga Partners Limited | Administrative & support | 2025 |
| Marty & Co (Cheltenham) Ltd | Construction | 2023 |
| Martyn Homer Leisure Limited | Wholesale & retail | 2025 |
| Marvel Fmcg Ltd | Professional & scientific | 2020 |
| Marwin Ltd | Information & communication | 2025 |
| Mary Mathacare Limited | Health & social care | 2021 |
| MAS International Food Ltd | Hospitality | 2026 |
| MAS Property Law Consulting Limited | Professional & scientific | 2016 |
| Masessi Limited | Health & social care | 2012 |
| Mason Kinch Ltd | Real estate | 2025 |
| Masonic Hall (Gloucester) Limited | Administrative & support | 1956 |
| Masons (Churchdown) Limited | Construction | 1978 |
| Master Sheds Ltd | Manufacturing | 2012 |
| Masterplan Limited | Extraterritorial | 2020 |
| Masterselection Limited | Hospitality | 2000 |
| Masterselection TOO Limited | Hospitality | 2006 |
| MAT Heating & Plumbing Services Ltd | Construction | 2026 |
| Match Fit Athlete Ltd | Administrative & support | 2025 |
| Mathew & Co Consultants Limited | Professional & scientific | 2025 |
| Mathewwaynedunn Limited | Professional & scientific | 2025 |
| Matson Avenue 1966 Limited | Extraterritorial | 2014 |
| Matt Felstead Ltd | Arts & recreation | 2020 |
| Matt Hale Tree Surgery Ltd | Agriculture & fishing | 2014 |
| Matt Law (UK) Limited | Professional & scientific | 2017 |
| Matt Murton Digital Ltd | Information & communication | 2019 |
| Matthew Burgoyne Limited | Financial services | 2017 |
| Matthew John Productions Limited | Information & communication | 2010 |
| Matthews HR Solutions Ltd | Professional & scientific | 2025 |
| Matty ROE Carpentry Ltd | Construction | 2024 |
| Matysek Ltd. | Professional & scientific | 2012 |
| Maurice J. Ruddy (Gloucester) Limited | Hospitality | 1975 |
| Maven Digital Limited | Information & communication | 2023 |
| MAW Trading Limited | Administrative & support | 2016 |
| Maxi Shop Ltd | Wholesale & retail | 2025 |
| Maxima Engineering and Software Services Limited | Information & communication | 2013 |
| Maximise Growth Limited | Professional & scientific | 2017 |
| Maxlie Limited | Financial services | 2024 |
| Maxpax Limited | Wholesale & retail | 2013 |
| Maxtron Limited | Wholesale & retail | 2021 |
| Maxx Impact Ltd | Information & communication | 2022 |
| MAY Group Lettings Ltd | Real estate | 2024 |
| MAY Hill Group Ltd | Manufacturing | 2017 |
| MAY James Lettings Ltd | Households | 2025 |
| MAY Olejnik Property Ltd | Real estate | 2026 |
| Mayfair Carpentry and Joinery Limited | Construction | 2003 |
| Mayfieldholidays Ltd | Agriculture & fishing | 2024 |
| Maymask (183) Limited | Administrative & support | 2012 |
| Mayuran Retail Ltd | Real estate | 2025 |
| MB Italian Ltd | Hospitality | 2022 |
| MB Joinery Cotswold Ltd | Construction | 2025 |
| MB Network Services Ltd | Information & communication | 2018 |
| MB Residences Ltd | Real estate | 2024 |
| MB Treads Ltd | Wholesale & retail | 2017 |
| MBB Logistic Ltd | Transport & logistics | 2020 |
| MBC Access Solutions Limited | Administrative & support | 2016 |
| MBD Festivals Ltd | Arts & recreation | 2018 |
| MBE Installations (Stroud) Limited | Manufacturing | 2010 |
| Mber Ltd | Manufacturing | 2021 |
| Mbis Convenience Store Ltd | Wholesale & retail | 2022 |
| MBK Logistics Ltd | Transport & logistics | 2024 |
| MBS Optimal Performance Group Ltd | Other services | 2025 |
| MC Connect Ltd | Administrative & support | 2024 |
| MC Construction Tools Limited | Wholesale & retail | 2019 |
| MC Legacy Assets Ltd | Real estate | 2024 |
| MCA Resin & Paving Ltd | Administrative & support | 2024 |
| Mcally Properties Limited | Households | 2018 |
| MCB Cyber Ltd | Information & communication | 2023 |
| Mccahill Holdings Ltd | Financial services | 2022 |
| Mccormick Holdings Limited | Real estate | 2022 |
| Mccoubrie Limited | Information & communication | 2025 |
| Mccoys BLA Ltd | Professional & scientific | 2023 |
| Mcdonnell Holdings Ltd | Real estate | 2021 |
| Mcdonnell-Price (Roofing) Contractors Limited | Construction | 2002 |
| MCE Group Limited | Manufacturing | 1990 |
| MCG Electrical Contractors Limited | Construction | 2011 |
| Mcgoldrick Hall Limited | Real estate | 2024 |
| Mcgonagle Windows & Doors Ltd | Construction | 2024 |
| Mcgregors of Cheltenham Ltd | Construction | 2022 |
| Mcguinness Group Ltd | Construction | 2016 |
| Mcguinness GRP Ltd | Construction | 2025 |
| Mcgurk Developments Limited | Extraterritorial | 2014 |
| Mcgurk Group LDN Ltd | Construction | 2019 |
| Mcgurk Group Limited | Professional & scientific | 2014 |
| Mcgurk Holdings Limited | Extraterritorial | 2015 |
| Mcgurk Land and Farms Limited | Real estate | 2018 |
| Mcgurk Limited | Extraterritorial | 2014 |
| Mcgurk PAY Limited | Administrative & support | 2022 |
| Mcgurk Properties Limited | Extraterritorial | 2014 |
| MCH Financial Solutions Ltd | Professional & scientific | 2011 |
| Mcintosh Builders Limited | Construction | 2019 |