| Moorside Tech Limited | Information & communication | 2018 |
| MOP & Magic Ltd | Administrative & support | 2025 |
| Morans Homes Ltd Ltd | Real estate | 2025 |
| Morar 75 Ltd | Transport & logistics | 2017 |
| Morebrooke Ltd | Construction | 2002 |
| Morgan Jasiok Ltd | Construction | 2023 |
| Morgcom 13 Ltd | Information & communication | 2026 |
| Morning Form Ltd | Wholesale & retail | 2023 |
| Morris & SON (Leeds) Limited | Wholesale & retail | 1996 |
| Morris and Gould Limited | Administrative & support | 2025 |
| Mortan Ltd | Hospitality | 2015 |
| Mosaac Financial Planning Limited | Financial services | 2012 |
| Mosaac Limited | Financial services | 2012 |
| Mosgeb Group Limited | Public administration | 2022 |
| Mother Pukka Nutrients Limited | Wholesale & retail | 2016 |
| Motiv Fitness Limited | Arts & recreation | 2024 |
| Motor Consultancy Ltd | Wholesale & retail | 2024 |
| Motorbing Limited | Wholesale & retail | 2019 |
| Motorhomes Properties Limited | Real estate | 2004 |
| Mount Lawley Homes Ltd | Real estate | 2025 |
| Mount Osborne Consultants Ltd | Professional & scientific | 2020 |
| Mount Pleasant Park Management Company Limited | Real estate | 2003 |
| Mount Properties (Yorkshire) Ltd | Real estate | 2025 |
| Move & Mend CIC | Education | 2025 |
| Moving Matters (UK) Limited | Construction | 2004 |
| Moyo Fresh Farm Supplies Ltd | Agriculture & fishing | 2019 |
| Mozvyc Ltd | Transport & logistics | 2026 |
| MPH & Bro's Services Ltd | Construction | 2020 |
| MPH Executive Ltd | Transport & logistics | 2023 |
| Mpongo Limited | Real estate | 2025 |
| MPR Entertainments Ltd | Arts & recreation | 2004 |
| MPS Scaffolding Limited | Construction | 2011 |
| Mpteam Ltd | Transport & logistics | 2024 |
| MPVETERINARYSERVICES2024 Ltd | Agriculture & fishing | 2024 |
| MR Blue Royston Limited | Wholesale & retail | 2025 |
| MRA Kitchen Limited | Hospitality | 2025 |
| MRC Groundworks Ltd | Construction | 2018 |
| MRD Consulting Ltd | Professional & scientific | 2025 |
| MRD Retail Ltd | Wholesale & retail | 2022 |
| MRS Walkers Rack Ltd | Wholesale & retail | 2026 |
| MRT Store Ltd | Wholesale & retail | 2024 |
| MS Autos (Barnsley) Limited | Wholesale & retail | 2025 |
| MS Barnsley Ltd | Wholesale & retail | 2025 |
| MS Cosmetics Ltd | Health & social care | 2011 |
| MS3 D Laboratory Ltd | Manufacturing | 2026 |
| Mseurotransport Limited | Transport & logistics | 2025 |
| MSG Haulage UK Ltd | Transport & logistics | 2025 |
| MSG Transport UK Ltd | Transport & logistics | 2023 |
| Msjs Products Limited | Wholesale & retail | 2024 |
| MSK Property Estates Ltd | Real estate | 2023 |
| MSL Plumbing and GAS Services Ltd | Construction | 2015 |
| MSM Deli Ltd | Hospitality | 2025 |
| MSM Foods S71 Ltd | Extraterritorial | 2019 |
| MSP Design and Consult Limited | Other services | 2007 |
| MSR Customs Ltd | Extraterritorial | 2024 |
| MSV Properties Ltd | Real estate | 2021 |
| MSW Enterprises Limited | Information & communication | 2005 |
| MT Auto Parts Ltd | Wholesale & retail | 2010 |
| MT Locum Services Limited | Health & social care | 2025 |
| MTB Consulting Group Ltd | Financial services | 2021 |
| MTB Logistics Ltd | Transport & logistics | 2025 |
| Mtds (Worksop) Ltd | Transport & logistics | 2014 |
| MTO Joinery Limited | Construction | 2021 |
| Much Loved Productions Limited | Arts & recreation | 1995 |
| Muck Movers Limited | Transport & logistics | 2025 |
| Muirfield Green Limited | Construction | 2021 |
| Mule Adventure Vans Ltd | Extraterritorial | 2024 |
| Mule Vans Ltd | Wholesale & retail | 2022 |
| Multi Access Scaffolding Limited | Construction | 2019 |
| Multi Alliance Group Ltd | Financial services | 2023 |
| Multi-Engineering Specialists Ltd | Professional & scientific | 2025 |
| Multiclean Ltd | Administrative & support | 2022 |
| Multilingual Solutions Ltd | Professional & scientific | 2023 |
| Multitekengineeringsolutions Ltd | Professional & scientific | 2025 |
| MUM BUM Ltd | Professional & scientific | 2026 |
| Mumbai Lounge a ALI Ltd | Hospitality | 2024 |
| Mundi Foods Ltd | Manufacturing | 2022 |
| Munks Property Limited | Real estate | 2018 |
| Munkymanagement Ltd | Construction | 2024 |
| Munkynest Ltd | Real estate | 2026 |
| Murdoch Investments UK Limited | Real estate | 2000 |
| Murton Gardens at Osbaldwick Management Company Limited | Real estate | 2005 |
| Muscle Hill Farm and Country Stores Limited | Wholesale & retail | 2018 |
| MUSE69 Limited | Wholesale & retail | 2024 |
| Musoni Electrics Ltd | Construction | 2018 |
| Mvmano Limited | Wholesale & retail | 2022 |
| MW Building & Construction Limited | Construction | 2023 |
| MW Coaching and Training Ltd | Education | 2023 |
| MW Online Merchant Limited | Wholesale & retail | 2023 |
| MW Profiles Ltd | Wholesale & retail | 2015 |
| Mwds Limited | Transport & logistics | 2007 |
| My Body Goals Ltd | Arts & recreation | 2021 |
| My Dessert Ltd | Hospitality | 2023 |
| My Dog Training Solutions Ltd | Other services | 2022 |
| My Energy Care UK Ltd | Construction | 2018 |
| My Happy Place Rentals Limited | Real estate | 2023 |
| My Life Choice Ltd | Health & social care | 2018 |
| My Medicard Ltd | Manufacturing | 2025 |
| My Pet Supplies Direct Ltd | Wholesale & retail | 2023 |
| Myaleo Ltd | Wholesale & retail | 2025 |