| Masuk Limited | Wholesale & retail | 2021 |
| Masuria Limited | Transport & logistics | 2025 |
| Masyl Trans Ltd | Transport & logistics | 2013 |
| MAT Finish Limited | Manufacturing | 2006 |
| Matagujry Limited | Hospitality | 2013 |
| Matarson Group Ltd | Real estate | 2024 |
| Match Properties Limited | Households | 1997 |
| Matdomara Ltd | Health & social care | 2021 |
| Matei Design Ltd | Professional & scientific | 2010 |
| Mateo BL Limited | Health & social care | 2024 |
| Mathan Consulting Limited | Professional & scientific | 2024 |
| Mathecor Ltd | Real estate | 2016 |
| Mathell Limited | Real estate | 2026 |
| Mati Group Limited | Transport & logistics | 2025 |
| Matikos Ltd | Transport & logistics | 2023 |
| Matran Logistics Ltd | Transport & logistics | 2016 |
| Matrix Recruitment and HR Ltd | Professional & scientific | 2024 |
| Matt Bottley Landscapes Limited | Administrative & support | 2012 |
| Matt Cripps Racing Ltd | Professional & scientific | 2024 |
| Matt Fiddes Martial Arts South LLP | | 2021 |
| Matt Gasnier Limited | Administrative & support | 2012 |
| Matt Neurotech Ltd | Information & communication | 2026 |
| Matt Oldfield Limited | Information & communication | 2019 |
| Matt Watts Media Ltd | Professional & scientific | 2022 |
| Matt Work Limited | Transport & logistics | 2020 |
| Matt's Bakery Limited | Hospitality | 2012 |
| Mattana UK Limited | Wholesale & retail | 2017 |
| Mattex Electrical Contractors Ltd | Construction | 2020 |
| Matthew Clift Decorating Services Ltd | Construction | 2025 |
| Matthew Ryle Limited | Financial services | 2019 |
| Matthew Trodd Dairies Ltd | Transport & logistics | 2009 |
| Mattu Construction Limited | Construction | 2026 |
| Mattymaty Ltd | Transport & logistics | 2025 |
| Matyko Cargo Ltd | Transport & logistics | 2023 |
| Maughan General Maintenance Limited | Construction | 2000 |
| Maurie's Sandwich Shop Ltd | Hospitality | 2024 |
| Maus Technology Ltd | Information & communication | 2023 |
| Mauson Assets Ltd | Administrative & support | 2009 |
| Mauson Assets Management Ukeig | | 2009 |
| MAV Synergy Ltd | Other services | 2019 |
| Maven Care Limited | Construction | 2005 |
| Maverick Barber Limited | Other services | 2019 |
| Maverick Card Payments Limited | Other services | 2019 |
| Maverick Muse Ltd | Information & communication | 2004 |
| Maverick Sewn Solutions Ltd | Manufacturing | 2025 |
| Mawgan Porth Holiday Park Limited | Hospitality | 1994 |
| Mawulisa Ltd | Manufacturing | 2022 |
| MAX Auto Mechanic Ltd | Wholesale & retail | 2025 |
| MAX Fried Chicken Ltd | Hospitality | 2023 |
| MAX Holmes Limited | Professional & scientific | 2013 |
| MAX Plumbing Supplies Limited | Wholesale & retail | 1999 |
| MAX Rollitt Antiques Ltd | Wholesale & retail | 2019 |
| MAX Rollitt Bespoke Limited | Wholesale & retail | 2021 |
| MAX Rollitt Ltd | Wholesale & retail | 2012 |
| Max's Deli Limited | Extraterritorial | 2014 |
| Max's Originals Ltd | Manufacturing | 2024 |
| Maxakoff Ltd | Professional & scientific | 2013 |
| Maxen Consultants Ltd | Professional & scientific | 2019 |
| Maxfame Limited | Hospitality | 2015 |
| Maxguard Storage Limited | Other services | 2025 |
| Maxhappyhouse Ltd | Health & social care | 2022 |
| Maxi IT Solutions Limited | Information & communication | 2011 |
| Maxia Global Ltd | Information & communication | 2026 |
| Maxiacre Limited | Real estate | 1982 |
| Maxim Pizza & Kebab Shop Limited | Hospitality | 2020 |
| Maxkor Tech Ltd | Construction | 2024 |
| Maxor Ltd | Information & communication | 2024 |
| Maxvmg Ltd | Administrative & support | 2006 |
| Maxwell Dando Limited | Financial services | 2020 |
| Maxwell-Being Hampshire Ltd | Other services | 2025 |
| MAY Amber Ltd | Administrative & support | 2018 |
| Maya Imports Limited | Wholesale & retail | 2024 |
| Maya Polish Supermarket Ltd | Wholesale & retail | 2014 |
| Mayanko Limited | Transport & logistics | 2025 |
| Maybush Barbers Limited | Other services | 2022 |
| Maybush Flat Management Company Limited | Households | 1988 |
| Maybush Stores Limited | Wholesale & retail | 2023 |
| Maycam Limited | Households | 2002 |
| Maycroft Court Management Company Limited | Real estate | 2014 |
| Maycroft Lodge Ltd | Construction | 2019 |
| Mayday Heating and Plumbing Ltd | Construction | 2019 |
| Mayday Personnel Services Limited | Administrative & support | 1988 |
| Mayday Property Services Limited | Real estate | 2024 |
| Mayfair Cotswolds Limited | Professional & scientific | 2021 |
| Mayfair Gardens Management Company (Southampton) Limited | Households | 1991 |
| Mayfair Hayling Island Limited | Real estate | 2019 |
| Mayfair Private Cars Ltd. | Transport & logistics | 2016 |
| Mayfair Romsey Limited | Professional & scientific | 2021 |
| Mayfair Wiltshire Limited | Real estate | 2018 |
| Mayfield Court Limited | Households | 1992 |
| Mayfield Moulds (LEE) Limited | | 1970 |
| Mayfield Nurseries | Health & social care | 2009 |
| Mayfield Properties Services Ltd | Real estate | 2019 |
| Mayflower Academy Limited | Arts & recreation | 2020 |
| Mayflower Enterprises Limited | Arts & recreation | 1996 |
| Mayflower Park Management Company Limited | Households | 2004 |
| Mayflower Pictures Limited | Information & communication | 2024 |
| Mayflower Productions (Southampton) Ltd | Arts & recreation | 2015 |
| Mayflower Property Services Limited | Real estate | 2017 |
| Mayflower Theatre Trust(The) | Arts & recreation | 1986 |