| M & a Catering Limited | Hospitality | 2015 |
| M & E Leonard Properties Ltd | Real estate | 2013 |
| M & M Rodway Carpentry and Joinery Limited | Construction | 1997 |
| M & S Shutters Ltd | Construction | 2025 |
| M a S T Eastwood Limited | Hospitality | 2018 |
| M Dunbar Electrical Limited | Construction | 2005 |
| M H Jointing Services Ltd | Construction | 2021 |
| M Hewing Holdings Ltd | Extraterritorial | 2018 |
| M Hodgins Electrical Contractors Ltd | Construction | 2014 |
| M J B Signs Ltd | Manufacturing | 2018 |
| M J H Controls Limited | Professional & scientific | 2014 |
| M L Lawrence Co Limited | Construction | 2003 |
| M L R Tooling Limited | Other services | 2004 |
| M P S Property Developments Limited | Construction | 2003 |
| M Pearson Roofing Ltd | Construction | 2023 |
| M S Automotive Limited | Professional & scientific | 2003 |
| M Shawyer Ceramics Ltd | Construction | 2021 |
| M T Flowers Limited | Wholesale & retail | 2014 |
| M Williams AM Limited | Financial services | 2026 |
| M&Es 1 Ltd | Hospitality | 2025 |
| M&H K Property Investments Limited | Hospitality | 2022 |
| M&Lbkr Consulting Ltd | Administrative & support | 2026 |
| M&N Properties Letting Ltd | Real estate | 2018 |
| M&R Utilities (UK) Ltd | Other services | 2014 |
| M&S Roofing & Guttering Ltd | Construction | 2023 |
| M&T Prescriptions Limited | Wholesale & retail | 2024 |
| M-Naks Energy Ltd | Professional & scientific | 2021 |
| M-Tech Controls Ltd | Construction | 2014 |
| M. Frost & Associates Ltd. | Construction | 2010 |
| M.A.N. Plumbing and Heating Limited | Construction | 2012 |
| M.B. Management Consultants Limited | Professional & scientific | 2018 |
| M.C.S. Property Services (UK) Limited | Real estate | 2006 |
| M.K.Aesthetic Clinic Limited | Other services | 2024 |
| M.R.S. Scientific Limited | Wholesale & retail | 1996 |
| M1ECC Antennas Limited | Information & communication | 2024 |
| M25 Steel Limited | Extraterritorial | 2013 |
| M8TRIX Property Maintenance Solutions Limited | Construction | 2023 |
| Macdonald Holdings Essex Limited | Construction | 2025 |
| Macdui Rehab Services Limited | Health & social care | 2015 |
| Macintyre London Ltd | Real estate | 2022 |
| Mackay Accounting Limited | Professional & scientific | 2017 |
| Mackenzie Webster Limited | Hospitality | 2025 |
| Mackers Total Recycling Ltd | Water & waste | 2010 |
| MAD Dogs & Englishmen Interiors Limited | Construction | 2012 |
| MAD Dogs and Englishmen Developments Limited | Construction | 2016 |
| MAD Dogs and Englishmen Holdings Limited | Real estate | 2020 |
| MAD JAM Films Limited | Administrative & support | 2013 |
| MAD JAM Properties Limited | Real estate | 2018 |
| Madden Van Hire Ltd | Administrative & support | 2020 |
| Made 4 Trades Ltd | Information & communication | 2021 |
| Mademoiselle Fifi Ltd | Wholesale & retail | 2019 |
| Madix Ltd | Transport & logistics | 2012 |
| Magic Monkey Leigh Ltd | Hospitality | 2022 |
| Magna Asset Holdings Limited | Real estate | 2026 |
| Magna Electrical Services Ltd | Construction | 2014 |
| MAID2CLEAN (Maidstone) Ltd | Administrative & support | 2018 |
| MAID2CLEAN (South East Region) Limited | Administrative & support | 2014 |
| Maile Electrical Contracting Limited | Construction | 2016 |
| Maile Electrical Ltd | Construction | 1996 |
| Maile Properties Limited | Extraterritorial | 2007 |
| Maine Consultancy Limited | Professional & scientific | 2018 |
| Maini Capital Group Limited | Financial services | 2023 |
| Maini Real Estate Limited | Real estate | 2023 |
| Mais Tech Limited | Information & communication | 2019 |
| Maisy Rose Flowers Ltd | Wholesale & retail | 2019 |
| Majer Windows Ltd | Manufacturing | 2006 |
| MAK Locums Limited | Health & social care | 2013 |
| Maker Trading Limited | Financial services | 2011 |
| Makeup.Ink Ltd | Other services | 2019 |
| Making Websites Better Limited | Information & communication | 2018 |
| Makkah Takeaway UK Ltd | Hospitality | 2024 |
| Malauta Ltd | Transport & logistics | 2015 |
| Maldon Mortgage Solutions Limited | Financial services | 2025 |
| Maldon Window Cleaning Limited | Administrative & support | 2018 |
| Malyons Mews Management Company Limited | Households | 2024 |
| Mami Management Ltd | Other services | 2020 |
| Mamma’S International UK Ltd | Wholesale & retail | 2024 |
| Managed Network Communications Limited | Wholesale & retail | 2003 |
| Managed Property Services (UK) Limited | Other services | 2013 |
| Mango Collins Design Ltd | Administrative & support | 2014 |
| Manix Air Conditioning Services Ltd | Energy | 2017 |
| Manners Corner Management Company Limited | Households | 1994 |
| Manor Dental Limited | Health & social care | 2021 |
| Manor Road SDM Limited | Health & social care | 2024 |
| Manor Trade Car Wash Limited | Wholesale & retail | 2025 |
| Manstage Barbers Ltd | Other services | 2023 |
| Manstage Limited | Other services | 2017 |
| Manston Mobility Limited | Wholesale & retail | 2014 |
| Mapes Properties Limited | Real estate | 2019 |
| Maple Court Management Limited | Real estate | 1991 |
| Maple Studios Ltd | Information & communication | 2021 |
| Maple Tree Surgery Limited | Agriculture & fishing | 2007 |
| Maplebush Engineering Limited | Administrative & support | 2013 |
| Mapletone Limited | Professional & scientific | 2023 |
| Marblake Properties Limited | Real estate | 2003 |
| Marc Gibb Ltd | Professional & scientific | 2019 |
| March Electrical Ltd | Construction | 2025 |
| Marchetti Contracts Limited | Hospitality | 2002 |
| Marco’S Polos Ltd | Wholesale & retail | 2024 |
| Margal Environmental Ltd | Construction | 2011 |