| Madlukas Limited | Transport & logistics | 2020 |
| Maeda Trading Ltd | Wholesale & retail | 2023 |
| Maenza Ltd | Real estate | 2022 |
| MAF Builders Ltd | Construction | 2014 |
| MAF Properties & Investments Ltd | Wholesale & retail | 2021 |
| Mafuva Consultancy Ltd | Information & communication | 2023 |
| Magazine Romanesc Luton Ltd | Wholesale & retail | 2024 |
| Magfeloh Ltd | Wholesale & retail | 2017 |
| Magic-Clean MK Ltd | Administrative & support | 2019 |
| Magicae Domos Limited | Households | 2022 |
| Magical Adventures Limited | Professional & scientific | 2000 |
| Magnova Ltd | Information & communication | 2024 |
| Magnum ICC UK R&D Ltd | Professional & scientific | 2024 |
| Magnus Transit Ltd | Transport & logistics | 2026 |
| Mags Holdings Ltd | Wholesale & retail | 2025 |
| Magyar Loan Instrument Trustee Limited | Professional & scientific | 2023 |
| Mahesh Bhatt Limited | Wholesale & retail | 2013 |
| Mahima Technical Services Ltd | Information & communication | 2025 |
| Mahona Energy Limited | Extraterritorial | 2002 |
| Maia Rehabilitation Limited | Health & social care | 2009 |
| Maid IT Sparkle Ltd | Administrative & support | 2023 |
| Mailroom Ltd | Information & communication | 2026 |
| Maimoona Ltd | Hospitality | 2014 |
| Main Group Holdings Limited | Professional & scientific | 2018 |
| Main Scaffolding Services Ltd | Construction | 2023 |
| Mainland Aggregates Ltd | Administrative & support | 2008 |
| Mainstream Systems Limited | Information & communication | 2006 |
| Maison LE Votre Ltd | Wholesale & retail | 2023 |
| Maison Management Services Limited | Administrative & support | 2019 |
| MAJ Administration Limited | Extraterritorial | 2007 |
| MAJ Investments Limited | Extraterritorial | 2007 |
| MAJ Services 2006 Limited | Extraterritorial | 2007 |
| Major Property Developments Ltd | Real estate | 2022 |
| Major Property Maintenance Ltd | Households | 2026 |
| Major Psychology Ltd | Health & social care | 2024 |
| Majorca Charters Ltd | Wholesale & retail | 2020 |
| Majorco Ltd | Real estate | 2023 |
| MAK Cars and Bikes Limited | Manufacturing | 2012 |
| MAK Estate Investments Ltd | Real estate | 2024 |
| MAK Precision Engineering Limited | Manufacturing | 2021 |
| MAK RR Ltd | Real estate | 2021 |
| MAK Studios (UK) Ltd | Information & communication | 2014 |
| MAK Surriya AF Limited | Health & social care | 2022 |
| Makandeni Capital Investments Holdings Limited | Financial services | 2021 |
| Makaq Ltd | Health & social care | 2025 |
| Makeitblue CIC | Health & social care | 2020 |
| Maker's Edge Ltd | Professional & scientific | 2026 |
| Makzeon Limited | Real estate | 2024 |
| Malabar General Maintenance Service Limited | Construction | 2025 |
| Malaplot Limited | Real estate | 1988 |
| Malbec Developments Ltd | Construction | 2021 |
| Malbourn Developments Limited | Real estate | 2016 |
| Malbourn Limited | Arts & recreation | 1994 |
| Maleah Homes Limited | Real estate | 2025 |
| Malick Solutions Ltd | Professional & scientific | 2025 |
| Mallowry Investments Ltd | Real estate | 2021 |
| Maltby Aero Engineering Consultancy Limited | Professional & scientific | 2015 |
| Mama Bear Nanny Services Ltd | Health & social care | 2023 |
| Mama Terri Groceries Ltd | Hospitality | 2023 |
| Mamuka Trading Ltd | Professional & scientific | 2025 |
| Mamuka UK Holdings Ltd | Financial services | 2025 |
| Mamuka UK Investments Ltd | Real estate | 2025 |
| Mamun Management Ltd | Real estate | 2017 |
| MAN & Sky Ltd | Transport & logistics | 2015 |
| MAN Barbers Ltd | Other services | 2024 |
| MAN Signature Solutions Limited | Construction | 2025 |
| Management Accounting & Support Services (Mass) Ltd | Professional & scientific | 2018 |
| Manaja Limited | Information & communication | 2015 |
| Manda UK Systems Limited | Transport & logistics | 2025 |
| Mandarin Research Limited | Professional & scientific | 2013 |
| Mandic Distribution Ltd | Transport & logistics | 2016 |
| Mandie Ltd | Health & social care | 2020 |
| Manek-Trans Ltd | Transport & logistics | 2019 |
| Manelli Construction Ltd | Construction | 2026 |
| MANGAL01 Ltd | Hospitality | 2026 |
| Manhill Housing Association Ltd | Administrative & support | 2014 |
| Mani's Pipefitting Services Ltd. | Construction | 2017 |
| Mann in Property Limited | Hospitality | 2025 |
| Mannar Services (UK) Ltd | Health & social care | 2014 |
| Manners DRY Lining Limited | Construction | 2009 |
| Mannu Law Ltd | Professional & scientific | 2022 |
| Manny Express Transport Limited | Transport & logistics | 2024 |
| Manolesorin Ltd | Transport & logistics | 2025 |
| Manon Fire & GAS Services Ltd | Wholesale & retail | 2019 |
| Manor Farm & Storage Limited | Agriculture & fishing | 2003 |
| Manor Farm Barns (Westoning) Management Company Limited | Administrative & support | 2014 |
| Manor Farm Contracting Limited | Agriculture & fishing | 2013 |
| Manor Farm Green Energy Limited | Manufacturing | 2015 |
| Manor House Interiors Ltd | Manufacturing | 2011 |
| Manor Mortgages Limited | Financial services | 2007 |
| Manor Park (Kathie Road) Management Company Limited | Households | 1999 |
| Manor Sourcing and Brokerage Ltd | Wholesale & retail | 2021 |
| Manpower Direct Ltd | Administrative & support | 2025 |
| Mansion House Services Limited | Administrative & support | 1987 |
| Manto Tech Limited | Information & communication | 2013 |
| Mantons Estate Agents Ltd | Real estate | 2018 |
| Mantons Properties Limited | Real estate | 2024 |
| MAP Diagnostics Limited | Professional & scientific | 2013 |
| Maple (349) Limited | Administrative & support | 2008 |
| Maple Automotive Ltd | Wholesale & retail | 2025 |