| Master Star Ltd | Administrative & support | 2020 |
| Masterclass Consult Limited | Transport & logistics | 2018 |
| Masterplay AV Ltd | Construction | 2022 |
| Masters Communications Consultancy Ltd | Administrative & support | 2023 |
| MAT (Trustees) Limited | Administrative & support | 2019 |
| MAT Recruitment Ltd | Administrative & support | 2018 |
| Matajm Consultancy Limited | Administrative & support | 2026 |
| Match My Motor Group Ltd | Financial services | 2018 |
| Matchbox Productions and Studios Limited | Wholesale & retail | 2020 |
| Matchbox Studios Ltd | Information & communication | 2026 |
| Matei Transport Services Ltd | Administrative & support | 2016 |
| Materialaway Ltd | Water & waste | 2026 |
| Mathan II Limited | Professional & scientific | 2022 |
| Mathminds Ltd | Information & communication | 2016 |
| Matico Limited | Administrative & support | 2016 |
| Matin Civil Limited | Professional & scientific | 2024 |
| Matren Limited | Information & communication | 2015 |
| Matrix Building Solutions Ltd | Construction | 2021 |
| Matrix Medical Writing Ltd | Health & social care | 2021 |
| Matrix Tuition Ltd | Education | 2024 |
| Matsop Limited | Administrative & support | 2025 |
| Matt Art Studio Limited | Education | 2025 |
| Matt Fryer Golf Limited | Education | 2020 |
| Matt Meir Cameras Ltd | Information & communication | 2020 |
| Matt's Travel Limited | Transport & logistics | 2019 |
| Matterello Ltd | Hospitality | 2019 |
| Matterhorn Consultancy Limited | Administrative & support | 2022 |
| Matterhorn Consulting London Limited | Professional & scientific | 2020 |
| Matthew Castle Construction Ltd | Administrative & support | 2025 |
| Matthew Coxon Psychology Services Limited | Health & social care | 2026 |
| Matthew Fenton Limited | Administrative & support | 2015 |
| Matthew James Vehicle Leasing Limited | Administrative & support | 2023 |
| Matthew Mcgreal Ltd | Administrative & support | 2014 |
| Matthew Singh Limited | Information & communication | 2020 |
| Matthew Wingrove Ltd | Professional & scientific | 2019 |
| Mattox Business Solutions Limited | Administrative & support | 2015 |
| Mattspe Ltd | Professional & scientific | 2020 |
| Mauwa Enterprises. Limited | Health & social care | 2022 |
| Mavan Measurement Limited | Administrative & support | 2007 |
| Mavcom Limited | Administrative & support | 2002 |
| Maven Radiology Limited | Health & social care | 2026 |
| Maverick Live Limited | Information & communication | 2020 |
| MAW Maintenance Ltd | Administrative & support | 2016 |
| MAW S&T Ltd | Administrative & support | 2023 |
| MAW Watertech Limited | Professional & scientific | 2019 |
| Mawdsley Developments Limited | Real estate | 2025 |
| Mawdsley Holdings Limited | Financial services | 2025 |
| Mawuli Electricals Limited | Construction | 2018 |
| MAX Bench Ltd | Administrative & support | 2026 |
| MAX Car Sales Ltd | Wholesale & retail | 2024 |
| MAX Car Wash Ltd | Administrative & support | 2025 |
| MAX Civil Engineering Ltd | Construction | 2007 |
| MAX Digital Healthcare Limited | Information & communication | 2024 |
| MAX Forklifts Ltd | Wholesale & retail | 2022 |
| MAX Glover Project Management Services Ltd | Professional & scientific | 2022 |
| MAX Telecom UK Limited | Information & communication | 2007 |
| Maxam Labs Ltd | Information & communication | 2022 |
| Maxcad Limited | Administrative & support | 2007 |
| Maximise Revenue Limited | Professional & scientific | 2020 |
| Maximum Licensing Limited | Professional & scientific | 2017 |
| Maximus Properties MCR Ltd | Real estate | 2022 |
| Maxit Partners Limited | Professional & scientific | 2017 |
| Maxwell Associates Group Ltd | Professional & scientific | 2025 |
| Maxwell Properties (Cheshire) Ltd | Real estate | 2024 |
| MAY Consulting UK Ltd | Education | 2006 |
| Maya 2025 Limited | Professional & scientific | 2025 |
| Maya Management Consulting Limited | Administrative & support | 2014 |
| Maycat Project Solutions Limited | Administrative & support | 2015 |
| Maydon Associates Building Consultancy Limited | Administrative & support | 2021 |
| Maydon Associates Ltd | Professional & scientific | 2018 |
| Mayer Parry (East Anglia) Limited | Extraterritorial | 1940 |
| Mayer Parry Recycling (Holdings) Limited | Extraterritorial | 1973 |
| Mayer Parry Recycling Limited | Extraterritorial | 1990 |
| Mayfield Holdings (NW) Ltd | Financial services | 2022 |
| Mayfield Homecare Services Limited | Administrative & support | 1999 |
| Mayfields Property Limited | Real estate | 2005 |
| Maylands Park Management Company Limited | Households | 2024 |
| Maynard & Conlan Limited | Wholesale & retail | 2022 |
| Mayo Social Ltd | Professional & scientific | 2024 |
| Mayoe Ltd | Health & social care | 2025 |
| Mayowa Data Services Limited | Administrative & support | 2025 |
| Maytree Lane Limited | Professional & scientific | 2021 |
| MAZ Mini Market UK Ltd | Wholesale & retail | 2025 |
| MAZ Project Solutions Ltd | Administrative & support | 2022 |
| MAZ Technologies Limited | Information & communication | 2018 |
| Mazana Projects Limited | Professional & scientific | 2011 |
| Mazongo Ltd | Health & social care | 2014 |
| MB & Marley Ltd | Administrative & support | 2026 |
| MB Estates (Cranage) Ltd. | Administrative & support | 2018 |
| MB IT Consulting Services Limited | Other services | 2018 |
| MB QA Limited | Administrative & support | 2015 |
| MB Sealants Limited | Construction | 2000 |
| MB Tech Warrington Limited | Wholesale & retail | 2006 |
| MBC Entertainments Limited | Hospitality | 2024 |
| MBC Property Maintenance Ltd | Real estate | 2026 |
| Mbcami Ltd | Public administration | 2022 |
| Mbcl Limited | Other services | 2018 |
| Mbekezeli Limited | Administrative & support | 2024 |
| Mbgo Limited | Other services | 2025 |
| MBM Technical Limited | Professional & scientific | 2018 |