| MC FUN Limited | Real estate | 2019 |
| MC Watches Limited | Wholesale & retail | 2024 |
| MC2 Wealth Limited | Financial services | 2009 |
| Mccrum & Co Limited | Professional & scientific | 2016 |
| Mcdonnell Developments Limited | Real estate | 2025 |
| Mcdowall Financial Consultants Limited | Administrative & support | 2015 |
| MCG Wealth Ltd | Financial services | 2014 |
| MCG Wealth NW Limited | Financial services | 2017 |
| Mcgill Structural Engineering Limited | Administrative & support | 2010 |
| Mcglinntech Limited | Wholesale & retail | 2021 |
| Mcgoff Construction Holdings Limited | Financial services | 2021 |
| Mcgoff Construction Limited | Construction | 1973 |
| Mcgoff Construction Services Limited | Financial services | 2023 |
| Mcgoff Group Facilities Services Limited | Administrative & support | 2015 |
| Mcgoff Group LLP | | 2007 |
| Mcgoff Group Projects (Helsby) Limited | Real estate | 2024 |
| Mcgoff Group Projects Limited | Construction | 2021 |
| Mcgoff Investco (Bowdon) Limited | Real estate | 2023 |
| Mcgoff Investco (Wilmsow) Limited | Real estate | 2024 |
| Mcgoff Support Services (Altair) Limited | Construction | 2021 |
| Mcgoff Support Services (Bobsleigh) Limited | Construction | 2019 |
| Mcgoff Support Services (Egerton) Limited | Construction | 2019 |
| Mcgoff Support Services (Lymm) Limited | Construction | 2017 |
| Mcgoff Support Services (Old Trafford) Limited | Financial services | 2020 |
| Mcgoff Ventures Limited | Financial services | 2019 |
| Mcguinness Football Consultancy Ltd | Arts & recreation | 2016 |
| MCH CAD Limited | Administrative & support | 2026 |
| Mchale Legal Limited | Professional & scientific | 2012 |
| Mchale Legal Trust Corporation Limited | Professional & scientific | 2024 |
| Mchale Sports Limited | Arts & recreation | 2015 |
| Mckee Insulations Ltd | Construction | 2025 |
| MCL A&A Propco Limited | Financial services | 2019 |
| MCL Coatings Limited | Construction | 2011 |
| MCL Devco Limited | Financial services | 2019 |
| MCL Gadbrook Propco Limited | Real estate | 2019 |
| MCL GJS Propco Limited | Financial services | 2019 |
| MCL HCC Propco Limited | Financial services | 2019 |
| MCL HQ Propco Limited | Financial services | 2019 |
| MCL KS Propco Limited | Financial services | 2019 |
| MCL Poland Limited | Financial services | 2020 |
| MCL Property Holdings Limited | Financial services | 2019 |
| MCL Property Hotel & Leisure Holdings Limited | Financial services | 2019 |
| MCL Property Hotel & Leisure Midco Limited | Financial services | 2019 |
| MCL Property Intermediate Holdings Limited | Financial services | 2019 |
| MCL Property Office & Industrial Holdings Limited | Financial services | 2019 |
| MCL Property Office & Industrial Midco Limited | Financial services | 2019 |
| MCL PV Propco Limited | Financial services | 2019 |
| MCL Residential 1 Limited | Financial services | 2020 |
| MCL Residential Holdco Limited | Financial services | 2020 |
| Mclaughlin Gould Ltd | Information & communication | 2018 |
| Mcmurrough Ltd | Education | 2020 |
| MCR Digital Marketing Limited | Professional & scientific | 2018 |
| MCR Lashes Ltd | Wholesale & retail | 2022 |
| MCR Real Estate II Ltd | Real estate | 2017 |
| MCR Repairs Ltd | Construction | 2024 |
| Mcspsvmaintenance Ltd | Wholesale & retail | 2024 |
| Mcvi Limited | Professional & scientific | 2009 |
| MD Medical Aesthetics Ltd | Health & social care | 2016 |
| Mdad Services Limited | Professional & scientific | 2023 |
| MDC Information Management Limited | Administrative & support | 2013 |
| MDQ Consulting Limited | Administrative & support | 2023 |
| Mdrm Ltd | Education | 2021 |
| MDS Consultancy Limited | Professional & scientific | 2022 |
| ME & MRS B Ltd | Wholesale & retail | 2024 |
| Meadowgate Engineering Limited | Professional & scientific | 2015 |
| Meadows Drinks Co Ltd | Manufacturing | 2016 |
| Meastim Developments Ltd | Construction | 2022 |
| Measure Twice CUT Once Limited | Other services | 2019 |
| Meba Consulting Limited | Professional & scientific | 2022 |
| Medallia Limited | Information & communication | 2012 |
| Media ARK Ltd | Information & communication | 2007 |
| Media Clarity Ltd | Professional & scientific | 2004 |
| Media IP Networks Limited | Information & communication | 1988 |
| Mediaguru Limited | Other services | 2014 |
| Mediataur Ltd | Information & communication | 2015 |
| Medical Collation and Chronology Limited | Administrative & support | 2015 |
| Medical Lasers and Ultrasound Technologies Ltd | Health & social care | 2003 |
| Medical Network Consultancy Ltd | Health & social care | 2012 |
| Medical Properties Limited | Real estate | 1991 |
| Medical Record Collation Limited | Professional & scientific | 2010 |
| Medical Workforce Solutions Ltd | Administrative & support | 2007 |
| Medicana International Limited | Real estate | 2023 |
| Medicana Winchester Limited | Health & social care | 2023 |
| Medicstar (UK) Limited | Wholesale & retail | 2010 |
| Mediknow Limited | Professional & scientific | 2018 |
| Medimis Limited | Information & communication | 2026 |
| Medimo Ltd | Information & communication | 2024 |
| Medisan Health Ltd | Wholesale & retail | 2017 |
| Medisure Healthcare Limited | Health & social care | 2012 |
| Mediterranean Olives Ltd | Wholesale & retail | 2026 |
| Medtech Operations Consultancy Ltd | Professional & scientific | 2025 |
| Meduserve Limited | Health & social care | 2009 |
| Medway Recruitment Ltd | Administrative & support | 2024 |
| Meed Consulting Limited | Professional & scientific | 2025 |
| Meehan Electrical Engineering Training & Safety Limited | Education | 2003 |
| Meera Consulting Ltd | Information & communication | 2012 |
| Mega Vyzia Limited | Administrative & support | 2011 |
| Melanie Cook Limited | Professional & scientific | 2018 |
| Melati Ltd | Wholesale & retail | 2023 |
| Melcryst Ltd | Health & social care | 2015 |