| MAE Grace Property Services Ltd | Real estate | 2024 |
| MAE Hospitality Ltd | Hospitality | 2025 |
| Maeve's Suffolk Ltd | Hospitality | 2023 |
| MAF Research Limited | Professional & scientific | 2019 |
| Maga Media LP | | 2011 |
| Magazin Romanesc Bacau Ltd | Wholesale & retail | 2021 |
| Magcal Ltd | Health & social care | 2023 |
| Magellan Media Limited | Professional & scientific | 2017 |
| Magenta Vision Ltd | Extraterritorial | 2025 |
| Magian Limited | Construction | 2007 |
| Magic Real State Ltd | Real estate | 2022 |
| Magic TR Limited | Construction | 2020 |
| Magic Word Media Ltd | Professional & scientific | 2018 |
| Magnolia Lodge (Loughton) Residents Limited | Administrative & support | 1997 |
| Magnus Events Limited | Hospitality | 2023 |
| Magor Enterprises Limited | Manufacturing | 2025 |
| Magpie (Suffolk) Ltd | Financial services | 2025 |
| Magpie Investments (Stonham) Limited | Real estate | 1993 |
| Magpie Road Bodyshop Ltd | Manufacturing | 2009 |
| Maharaja Felixstowe Ltd | Hospitality | 2025 |
| Maharani Ipswich Ltd | Hospitality | 2025 |
| Maharishi Garden Village Apartments Limited | Households | 2008 |
| Mahgon Medical Solutions Limited | Health & social care | 2023 |
| Maid in Surrey Hills Limited | Administrative & support | 2024 |
| MAID2CLEAN (Suffolk) Ltd | Other services | 2009 |
| Maidenhall Green Ltd | Hospitality | 2025 |
| Mainstay Architecture Ltd | Professional & scientific | 2024 |
| Maintenx Ltd | Transport & logistics | 2024 |
| Mainway Services Ltd | Health & social care | 2022 |
| Maison Developments (MI) Limited | Construction | 2022 |
| Maison Investments Limited | Real estate | 2017 |
| Maitland Homes Limited | Construction | 1996 |
| MAJ Driver Hire Ltd | Transport & logistics | 2026 |
| Majesteye Ltd | Information & communication | 2021 |
| Majestic Carpet Cleaning Ltd | Administrative & support | 2025 |
| Majestty Properties Limited | Real estate | 2019 |
| Major Performance Developments Limited | Manufacturing | 2025 |
| Major Social Care Solutions Ltd | Health & social care | 2017 |
| MAK Real Estate Limited | Real estate | 2018 |
| Makax Ltd | Construction | 2025 |
| Makax Properties Ltd | Real estate | 2026 |
| Make Play CIC | Education | 2022 |
| Makeney Holidays Limited | Hospitality | 2020 |
| Maketh Secure Limited | Information & communication | 2023 |
| Making Life Feel Better Limited | Health & social care | 2023 |
| Makson Contracts Limited | Construction | 2016 |
| Malabar Delights Ltd | Hospitality | 2025 |
| Malat Limited | Hospitality | 2019 |
| Malek Ipswich Ltd | Hospitality | 2019 |
| MALIN23 Ltd | Transport & logistics | 2024 |
| Maljon (Timber Preservation)Limited | Construction | 1971 |
| Malka Cleaning Ltd | Administrative & support | 2024 |
| Mallaby Investments Limited | Construction | 2025 |
| Mallory Franklin Ltd | Arts & recreation | 2020 |
| Mallowhayes Properties Limited | Real estate | 2017 |
| Maltings Entertainment Limited | Arts & recreation | 2014 |
| Maly IT Solutions Limited | Information & communication | 2009 |
| Mama Bears Cake Bar Ltd | Manufacturing | 2021 |
| Mama HUG Ltd | Wholesale & retail | 2019 |
| Mamadee Ltd | Wholesale & retail | 2025 |
| Mamba Martial Arts Limited | Arts & recreation | 2019 |
| Mammalian Limited | Administrative & support | 2025 |
| Mammoth Consulting Ltd | Education | 2018 |
| Mamut Cargo Limited | Transport & logistics | 2023 |
| MAN Kind Movement CIC | Education | 2026 |
| Mana Baby Diapers Ltd | Wholesale & retail | 2025 |
| Manabu 121 Ltd | Education | 2024 |
| Manael Ltd | Professional & scientific | 2025 |
| Manage the Detail Limited | Administrative & support | 2014 |
| Managed Healthcare Limited | Other services | 2015 |
| Managing Matters Ltd | Administrative & support | 2022 |
| Manake Cleansing Salts and Herbs Limited | Wholesale & retail | 2023 |
| Manaseh Ltd | Transport & logistics | 2017 |
| Manaseh Properties Limited | Real estate | 2022 |
| Manav Trading Limited | Other services | 2016 |
| Mandarin Associates Limited | Information & communication | 1999 |
| Mangir Ltd | Hospitality | 2026 |
| Manica Delights Ltd | Manufacturing | 2016 |
| Manifesto Woman Limited | Professional & scientific | 2016 |
| Mann Brickwork Ltd | Construction | 2019 |
| Mann Couchman (UK) Limited | Information & communication | 2020 |
| Manns Family Butchers Limited | Wholesale & retail | 2016 |
| Mannsafe Security Ltd | Administrative & support | 2018 |
| Manny Drives Ltd | Administrative & support | 2020 |
| Manor Avenue NO 22 Limited | Households | 2005 |
| Manor Farm Coffee Shop Limited | Hospitality | 2015 |
| Manor House (Felixstowe) Limited | Real estate | 1965 |
| Manor House Investments Ipswich Ltd | Real estate | 2022 |
| Manor IFA Limited | Financial services | 2000 |
| Manor Investments (Ipswich) Limited | Real estate | 1996 |
| Manor Investments (Paragon) Limited | Real estate | 1999 |
| Manor Travel Ltd | Other services | 2025 |
| Manormaker (Nominee NO. 1) Limited | Real estate | 2015 |
| Manormaker (Nominee NO. 2) Limited | Real estate | 2015 |
| Manormaker GP Limited | Real estate | 2010 |
| Manorside Travel Ltd | Other services | 2017 |
| Manpineco Limited | Wholesale & retail | 2007 |
| Mansfield Towers Management Co. Limited | Households | 1992 |
| Mansion House Bedding Group Limited | Manufacturing | 2011 |
| Mansion House Holdings Limited | Manufacturing | 2003 |