| Maheshwar Builder Limited | Construction | 2025 |
| Maheshwari Mahasabha UK | Other services | 2009 |
| Mahfar Limited | Health & social care | 2014 |
| Mahi Mahi Sushi Limited | Wholesale & retail | 2025 |
| Mahi Restaurants Limited | Hospitality | 2018 |
| Mahidharia Locums Ltd | Professional & scientific | 2024 |
| Mahipar Ltd | Hospitality | 2026 |
| Mahiparfish Ltd | Hospitality | 2026 |
| Mahir Catering Ltd | Hospitality | 2023 |
| Mahira Tech Ltd | Information & communication | 2025 |
| Mahmood Alam Cloth Ltd | Wholesale & retail | 2024 |
| Mahoe PPM Solutions Limited | Professional & scientific | 2015 |
| Mahrady Ltd | Wholesale & retail | 2023 |
| Mahris Consulting Ltd | Professional & scientific | 2019 |
| Mahtab Enterprises Limited | Wholesale & retail | 2026 |
| Mahvels Limited | Information & communication | 2014 |
| Mahzey Ltd | Hospitality | 2011 |
| Mai-Kee Tsang Media Ltd | Other services | 2022 |
| Maid Pro Ltd | Administrative & support | 2021 |
| Maij Limited | Professional & scientific | 2022 |
| Mailwise Ltd | Professional & scientific | 2024 |
| Mainline (1982) Limited | Administrative & support | 1990 |
| Mainline Roofing Limited | Construction | 2021 |
| Mainplan Limited | Construction | 2016 |
| Mainstone Consulting Limited | Health & social care | 2020 |
| Mainstream Services Ltd | Professional & scientific | 2017 |
| Maintenance Doctor Ltd | Construction | 2025 |
| Maintenance Guru Ltd | Construction | 2018 |
| Maishco Limited | Health & social care | 2010 |
| Maison Duvall Ltd | Construction | 2025 |
| Maison Mère Studio Ltd | Arts & recreation | 2025 |
| Maison Touch Limited | Information & communication | 2025 |
| Maithili Makeup Ltd | Other services | 2024 |
| Maitland Assets Limited | Other services | 2013 |
| Maitland Projects Limited | Construction | 2010 |
| Maitland Road Limited | Construction | 2011 |
| Maiwand Martial Arts GB Ltd | Arts & recreation | 2019 |
| Major Care Homes Limited | Health & social care | 2021 |
| Major Estates (Harrow) Limited | Real estate | 2014 |
| Major Estates Financial Services Limited | Financial services | 1998 |
| Majoramens Limited | Wholesale & retail | 2020 |
| MAK E&A (UK) Company Limited | Wholesale & retail | 2023 |
| MAK Living Limited | Real estate | 2025 |
| MAK Logistics Ltd | Transport & logistics | 2011 |
| MAK Plus Limited | Professional & scientific | 2022 |
| MAK Returns Limited | Real estate | 2021 |
| Make a Mask Limited | Arts & recreation | 2012 |
| Make From Scratch Limited | Administrative & support | 2018 |
| Make Great Homes Limited | Real estate | 2021 |
| Make Lonely Limited | Construction | 2022 |
| Make Natural Limited | Professional & scientific | 2009 |
| Make Perfect Construction Limited | Construction | 2017 |
| Make UP Properties Ltd | Real estate | 2016 |
| Makeandjoy Limited | Wholesale & retail | 2026 |
| Makesworth Audit Services Ltd | Professional & scientific | 2018 |
| Makesworth Investments & Holdings Ltd | Real estate | 2022 |
| Makesworth Limited | Professional & scientific | 2012 |
| Makesworth MK Ltd | Professional & scientific | 2022 |
| Makesworth Support Services Ltd | Administrative & support | 2022 |
| Makesworth Tax Advisers Ltd | Professional & scientific | 2016 |
| Makewell Europe Limited | Wholesale & retail | 2019 |
| Makiba Property Limited | Real estate | 2026 |
| Making Doctors Ltd | Administrative & support | 2018 |
| Makkys Furnishers UK Ltd | Professional & scientific | 2025 |
| Makova Ltd | Wholesale & retail | 2026 |
| Maksons Properties Harrow Ltd | Real estate | 2021 |
| Maksons Properties Ltd | Real estate | 2015 |
| Maktech Limited | Information & communication | 2011 |
| Mala Hair Salon Ltd | Other services | 2020 |
| Malabar Estates Limited | Real estate | 2000 |
| Malabari Group Ltd | Hospitality | 2024 |
| Malangco Limited | Administrative & support | 1980 |
| Malasa Limited | Wholesale & retail | 2020 |
| Malay Rose Heart/Goddessescape Travel Ltd | Wholesale & retail | 2017 |
| Malchut Properties Limited | Real estate | 2025 |
| Malcolm Schaller Limited | Health & social care | 2020 |
| Malde Consultancy Services Ltd. | Administrative & support | 2011 |
| Malde Partners LLP | | 2021 |
| Malden Properties Limited | Real estate | 2016 |
| Malfi Electric Ltd | Energy | 2026 |
| Malford Grove Consulting Limited | Professional & scientific | 2009 |
| Malgaro Limited | Professional & scientific | 2012 |
| Malik & Waring Orthodontists Limited | Health & social care | 2006 |
| Malik & Waring Properties Limited | Real estate | 2023 |
| Malik Electronics Communication International Ltd | Construction | 2024 |
| Malik Orthodontists Ltd | Financial services | 2025 |
| Maliki Sharie Limited | Construction | 2018 |
| Malikorthopaedics Ltd | Health & social care | 2024 |
| Malino World Martial Art Excellence Ltd | Wholesale & retail | 2018 |
| Malix Limited | Real estate | 2023 |
| Malkishan Limited | Real estate | 2017 |
| Malla Building Limited | Construction | 2026 |
| Mallard Incorporated Limited | Real estate | 2016 |
| Mallard Residents Association Limited | Households | 1979 |
| Mallard Solutions Ltd | Construction | 2018 |
| Mallards & Manor Ltd | Wholesale & retail | 2024 |
| Malmac Developments Limited | Construction | 2024 |
| Malmswood Farm Limited | Agriculture & fishing | 1993 |
| Malolan Limited | Information & communication | 2011 |
| Malson UK Limited | Wholesale & retail | 2019 |