| MGS Contracts Group Ltd | Construction | 2026 |
| MH (CBS) Limited | Financial services | 2023 |
| MH (GB) Limited | Financial services | 2000 |
| MH Cooper Ltd | Professional & scientific | 2026 |
| MH Management(London) Limited | Administrative & support | 2017 |
| Mhfgc Limited | Other services | 2021 |
| MHJ Investments Limited | Real estate | 2014 |
| MHN Group Limited | Real estate | 2025 |
| MHN Holdings Limited | Real estate | 2018 |
| Mhub POS Ltd | Other services | 2013 |
| MI Dental Implants Ltd | Health & social care | 2023 |
| MI Training Ltd | Construction | 2024 |
| MIA Building Services Limited | Administrative & support | 2011 |
| MIA Leisure Limited | Arts & recreation | 2022 |
| MIB Consulting Ltd | Wholesale & retail | 2019 |
| MIB Property Management Ltd | Extraterritorial | 2022 |
| Mibodyx Injury & Performance Clinic Ltd | Health & social care | 2022 |
| Michael Building Corporation Ltd | Construction | 2020 |
| Michai & Michael Jarrett Catering Services Ltd | Hospitality | 2025 |
| Michel Ghatan Photography Limited | Professional & scientific | 2020 |
| Michelle Noel Limited | Professional & scientific | 2009 |
| Micro Antz Ltd | Information & communication | 2022 |
| Microfluidx Ltd | Manufacturing | 2018 |
| Micrologic Computer Systems Limited | Professional & scientific | 1996 |
| Middle ROW Records Limited | Wholesale & retail | 2018 |
| Mightyit Limited | Information & communication | 1997 |
| Mikado Investments Ltd | Real estate | 2020 |
| Mike Edwards Ltd | Construction | 2017 |
| Mike's Windows Ltd | Construction | 2019 |
| Mila Carer Ltd | Construction | 2022 |
| Milburn Site Services Ltd | Administrative & support | 2018 |
| Milejet Limited | Health & social care | 2018 |
| Milejet Properties Limited | Real estate | 2021 |
| Milin Ltd | Wholesale & retail | 2025 |
| Milinol Ltd | Professional & scientific | 2024 |
| Milk and Honey the Movie Limited | Information & communication | 2015 |
| Milk Line Music Ltd | Information & communication | 2019 |
| Milk Line Records Ltd | Information & communication | 2019 |
| Milkylife Dairies Ltd | Wholesale & retail | 2018 |
| Mill Marketing Ltd | Professional & scientific | 2026 |
| Mill Street Hotels Ltd | Health & social care | 2022 |
| Millennium 7 Studios Ltd | Information & communication | 2025 |
| Millstream Plumbing Limited | Construction | 2017 |
| Millwell Oakhurst Limited | Information & communication | 2025 |
| Milly Sands Interiors Ltd | Wholesale & retail | 2020 |
| Mimic Stage School Ltd | Arts & recreation | 2025 |
| Mimram Media Limited | Professional & scientific | 2014 |
| Mind Your Business Group Ltd | Real estate | 2024 |
| Mindmap Specialist Ltd | Health & social care | 2026 |
| Minerva Bidco Limited | Professional & scientific | 2018 |
| Minerva Debtco Limited | Professional & scientific | 2018 |
| Minerva Equity Limited | Professional & scientific | 2018 |
| Minerva Holdco Limited | Professional & scientific | 2018 |
| Minerva Parent Limited | Professional & scientific | 2018 |
| Minor Details Royston Ltd | Wholesale & retail | 2026 |
| Minotaur Gym Ltd | Arts & recreation | 2021 |
| Mint Films Ltd | Information & communication | 2002 |
| Mint Lettings and Management Ltd | Real estate | 2010 |
| Mint Motors Garage Workshop Limited | Wholesale & retail | 2026 |
| Minute Pictures Limited | Information & communication | 2024 |
| Miotas Ltd | Arts & recreation | 2019 |
| Mira Electrical Ltd | Energy | 2017 |
| Miracall Solutions Limited | Information & communication | 2003 |
| Mirandy Property Ltd | Real estate | 2025 |
| Miraval Limited | Information & communication | 2014 |
| Miroslawa Klobukowska Ltd | Health & social care | 2020 |
| Misi Care Limited | Health & social care | 2014 |
| Missfits Salons Limited | Other services | 2025 |
| Misya Cakes Ltd | Manufacturing | 2025 |
| Misya Food Centre Limited | Wholesale & retail | 2020 |
| Misya Steveneage Ltd | Hospitality | 2023 |
| Mitchell Rights Management Limited | Administrative & support | 2016 |
| Mitchell’S Heating & Plumbing Limited | Construction | 2023 |
| MITM2015 Ltd | Hospitality | 2025 |
| Mitres Touch Limited | Other services | 2022 |
| Mitus Trading Limited | Other services | 2011 |
| Miu-Csa Consulting Ltd | Information & communication | 2018 |
| Miyagi Bonsai Limited | Arts & recreation | 2020 |
| MJ Havora Care & Living Ltd | Health & social care | 2026 |
| Mjaj Services Limited | Construction | 2025 |
| Mjgm Productions Limited | Construction | 2024 |
| MJH Kenilworth Consulting Limited | Professional & scientific | 2018 |
| MJH Plumbing & Drainage Limited | Construction | 2010 |
| MJH Vehicle Management Ltd | Administrative & support | 2026 |
| Mjlj Services Limited | Construction | 2022 |
| MJM Windows Limited | Administrative & support | 2021 |
| MJR Event Services Limited | Manufacturing | 2024 |
| MJR Sales Consulting Limited | Professional & scientific | 2024 |
| MJS Construction Services Limited | Other services | 2019 |
| MK Tiles Ltd | Wholesale & retail | 2006 |
| Mkaw Limited | Information & communication | 2017 |
| Mkek Enterprises Ltd | Professional & scientific | 2021 |
| MKG (Hertfordshire) Limited | Wholesale & retail | 1992 |
| MKS Asset Group Limited | Real estate | 2024 |
| MKT General Services Ltd | Construction | 2024 |
| ML Repair Smart Limited | Wholesale & retail | 2015 |
| MLE Construction Holdings Limited | Financial services | 2017 |
| MLE Construction Limited | Construction | 2015 |
| MLJ Designs Ltd | Professional & scientific | 2023 |
| Mlmedical Limited | Health & social care | 2026 |