| Mohseni Property Services Limited | Construction | 2011 |
| MOI ME Ltd | Health & social care | 2021 |
| Mojab Ltd | Health & social care | 2025 |
| Mojo Business Solutions Ltd | Information & communication | 2011 |
| Mojo LG Ltd | Information & communication | 2025 |
| Mokobane Maliehe Ltd. | Health & social care | 2014 |
| Mollands Holdings Limited | Financial services | 2026 |
| Momentum Event Solutions Limited | Hospitality | 2026 |
| Monade Care Services Ltd | Health & social care | 2013 |
| Monarch Development Construction Ltd | Construction | 2021 |
| Monarch Homes Limited | Real estate | 1977 |
| Moneris Ltd | Professional & scientific | 2026 |
| Moneyquest Mortgage Brokers Limited | Financial services | 2008 |
| Monk Construction Ltd | Construction | 2011 |
| Monkey Locks Limited | Manufacturing | 2026 |
| Monksfield Holdings Limited | Real estate | 2022 |
| Monolink Limited | Administrative & support | 2004 |
| Monolithedge Construction Ltd | Construction | 2025 |
| Montana Mgmt Ltd | Other services | 2026 |
| Montgomery Coaching & Consultancy Limited | Administrative & support | 2022 |
| Montgomery Steel Services Ltd | Construction | 2026 |
| Montrose Projects Limited | Construction | 2011 |
| Moodjig Ltd | Professional & scientific | 2025 |
| Moorcroft Contracts Limited | Construction | 2023 |
| Moores T2 Ltd | Construction | 2025 |
| Mooreways Scaffolding Limited | Construction | 2011 |
| Mopomart Ltd | Information & communication | 2019 |
| Mopothecary Ltd | Public administration | 2024 |
| Morales Lettings Ltd | Real estate | 2022 |
| Morandy Ltd | Construction | 2018 |
| Morash Consultancy Limited | Information & communication | 2016 |
| Morayol Ltd | Construction | 2020 |
| More Depth Media Ltd | Professional & scientific | 2019 |
| More Than Numbers Ltd | Professional & scientific | 2011 |
| Morgan Integrated Security Solutions Limited | Other services | 2017 |
| Morgun & White Limited | Transport & logistics | 2022 |
| Morrell Media Group Limited | Information & communication | 2025 |
| Morrells Builders Limited | Construction | 2017 |
| Morris Holdings Ltd | Real estate | 2015 |
| Morris Landscapes Ltd | Administrative & support | 2022 |
| Morse Coaching and Consulting Ltd | Professional & scientific | 2022 |
| Mortbrick Enterprises Ltd | Wholesale & retail | 2025 |
| Mortgage Support Services Ltd | Professional & scientific | 2007 |
| Mortimer BTL 2022-1 PLC | Financial services | 2022 |
| Mortimer Road (Willow Mews) MAN. Co. Ltd. | Professional & scientific | 2021 |
| Mortimers Estate Agents Woodbridge Limited | Real estate | 2023 |
| Morton House Properties Ltd | Real estate | 2026 |
| Mose Cafe Ltd | Hospitality | 2024 |
| Mossford Construction Company Limited | Construction | 2008 |
| Motautocare Limited | Wholesale & retail | 2023 |
| Motianx Care Limited | Financial services | 2025 |
| Motion Associates Ltd | Arts & recreation | 2010 |
| Motion AV Limited | Information & communication | 2018 |
| Motormobile Limited | Wholesale & retail | 2026 |
| Motorworld Media Limited | Information & communication | 2013 |
| Mott Construction Limited | Construction | 2024 |
| Mountainwolves Ltd | Transport & logistics | 2021 |
| Mountdale Limited | Health & social care | 2012 |
| Mountdale Properties Limited | Real estate | 2023 |
| Mountnessing Road 2026 Ltd | Construction | 2026 |
| Move ANY Car Ltd | Transport & logistics | 2025 |
| Move U Limited | Wholesale & retail | 2021 |
| Movesphere Logistics Ltd | Transport & logistics | 2026 |
| Moviccare Limited | Wholesale & retail | 2023 |
| Movin ME Limited | Professional & scientific | 2019 |
| MOW 2017 Limited | Transport & logistics | 2017 |
| Mozaic Inc Ltd | Professional & scientific | 2018 |
| MP Data Solutions Ltd | Information & communication | 2023 |
| MP Deployments Ltd | Information & communication | 2015 |
| MP GAS and Plumbing Ltd | Construction | 2017 |
| MP Thermal Ltd | Construction | 2019 |
| Mp&F Properties Limited | Real estate | 2025 |
| MPE General Holdings Limited | Construction | 2008 |
| MPI Developments Limited | Real estate | 2015 |
| MPI Management Limited | Construction | 2015 |
| MR & MRS Toy Ltd | Wholesale & retail | 2015 |
| MR Cellphone Basildon Ltd | Wholesale & retail | 2024 |
| MR Sparks 20 Ltd | Wholesale & retail | 2025 |
| MRB3 Limited | Construction | 2017 |
| MRE Group Holdings Limited | Professional & scientific | 2016 |
| MRF Mechanical Services Essex Limited | Construction | 2026 |
| MRG Homes Ltd | Real estate | 2025 |
| MRS Food Ltd | Hospitality | 2025 |
| Mrskully Limited | Information & communication | 2014 |
| MRT Contracts Ltd | Construction | 2012 |
| MS Curryhouse Ltd | Hospitality | 2019 |
| MSB Basildon Ltd | Professional & scientific | 2017 |
| MSD Martial Arts Limited | Administrative & support | 2010 |
| MSD Transport Solutions Ltd | Extraterritorial | 2021 |
| MSH10 Holdings Ltd | Wholesale & retail | 2019 |
| Msln Holdings Limited | Financial services | 2024 |
| MSM Construction Solutions Ltd | Construction | 2012 |
| MSM Fibreglass Ltd | Manufacturing | 2023 |
| MSR Essex Ltd | Construction | 2025 |
| MSR Homes Limited | Other services | 2020 |
| MSR Services Ltd | Professional & scientific | 2025 |
| MSW Financial Services Ltd | Professional & scientific | 2021 |
| MSY UK Investments Ltd | Real estate | 2025 |
| MT Construtions Limited | Real estate | 2024 |
| MT Europe Ltd | Administrative & support | 2020 |