| Michian Developments Ltd | Real estate | 2025 |
| Michvic Homes Estate Limited | Real estate | 2026 |
| Mick Stevenson Limited | Construction | 2017 |
| Mickblade Ltd | Administrative & support | 2016 |
| Micon Urban Ltd | Real estate | 2017 |
| Micro IT Components Limited | Transport & logistics | 2007 |
| Micro Precision (Yorkshire) Ltd | Professional & scientific | 1979 |
| Microbiological Validation Services Ltd | Professional & scientific | 2003 |
| Microblade (Holdings) Limited | Financial services | 1985 |
| Microboard Limited | Information & communication | 1999 |
| Microck Ltd | Wholesale & retail | 2023 |
| Microfilm Business Systems Limited | Administrative & support | 1990 |
| Microinsight Limited | Information & communication | 2016 |
| Microlec Limited | Manufacturing | 1985 |
| Micromart International Limited | Wholesale & retail | 2017 |
| Micron-Ellis Limited | Manufacturing | 1977 |
| MID - Way Developments Limited | Construction | 2006 |
| Midas Sourcing & Consultancy Limited | Professional & scientific | 2019 |
| Midcity Estates Holdings Limited | Real estate | 2023 |
| Midcity Estates Limited | Real estate | 1999 |
| Midcity Estates Management Limited | Hospitality | 2005 |
| Middleton Bell Ecology Ltd | Professional & scientific | 2022 |
| Middleton Carrstone Limited | Manufacturing | 1978 |
| Middleton Creative Limited | Information & communication | 2020 |
| Middleton Psychology Limited | Health & social care | 2009 |
| Middletons D I Y Ltd | Wholesale & retail | 2006 |
| Middletons Letting and Property Management Limited | Real estate | 2021 |
| Middlewood Carpets Ltd | Wholesale & retail | 2021 |
| Middlewood Environmental Limited | Professional & scientific | 2010 |
| Middlewood Food Ltd | Hospitality | 2024 |
| Middlewood Investments Limited | Real estate | 1961 |
| Middlewood Lodge Sheffield Management Company Limited | Households | 2007 |
| Middlewood Road Management Company Limited | Real estate | 2016 |
| Middlewood Soap & Shine Ltd | Administrative & support | 2025 |
| Midgley's Properties Limited | Real estate | 1970 |
| Midl NO3 Ltd | Real estate | 2020 |
| Midland Classic M.C.C. Limited | Arts & recreation | 1992 |
| Midland Renewables Limited | Construction | 2013 |
| Midlands Engine Investments Limited | Financial services | 2016 |
| Midlands Marketing Media Limited | Professional & scientific | 2009 |
| Midlands Video Systems Ltd. | Extraterritorial | 1987 |
| Midnight Feast Productions Ltd | Information & communication | 2025 |
| Midnight Kitty Limited | Manufacturing | 2012 |
| Midoki Limited | Information & communication | 2011 |
| Midvale 1966 Limited | Extraterritorial | 2013 |
| Midwinter OIL Supplies Limited | Extraterritorial | 1988 |
| Miers Construction Products Limited | Wholesale & retail | 2010 |
| Miffa Limited | Information & communication | 2019 |
| Migami Groupe Limited | Other services | 2023 |
| Mighty Fast Food Ltd | Hospitality | 2025 |
| Mighty Marketing UK Limited | Administrative & support | 2008 |
| Mightyscope Ltd | Information & communication | 2025 |
| MIH Accident Management Ltd | Other services | 2015 |
| MIH Medical Ltd | Health & social care | 2012 |
| MIH Properties Ltd | Real estate | 2017 |
| Mihai Toma Repairs Ltd | Wholesale & retail | 2023 |
| Mihoms Limited | Real estate | 2025 |
| MIJ & Co Entertainment Limited | Professional & scientific | 2017 |
| MIJ Masks Limited | Other services | 2019 |
| MIJ Productions Limited | Professional & scientific | 2025 |
| MIK9 Services Ltd | Administrative & support | 2026 |
| Mika Building Ltd | Construction | 2023 |
| Mika Electronics Ltd | Wholesale & retail | 2024 |
| Mike Bramall & Co Limited | Professional & scientific | 2000 |
| Mike Brewer Motors Ltd | Wholesale & retail | 2010 |
| Mike Clayton RPE Consultancy Ltd | Professional & scientific | 2020 |
| Mike Hartley Construction Limited | Construction | 2016 |
| Mike Insley Limited | Professional & scientific | 2015 |
| Mike Kidder Associates Limited | Professional & scientific | 2011 |
| Mike Lawrence CIC | Education | 2024 |
| Mike Lawrence Mental Health & Wellbeing Management Consultancy Limited | Extraterritorial | 2022 |
| Mike Lewis Agencies Limited | Wholesale & retail | 2007 |
| Mike Moran Music Limited | Information & communication | 2022 |
| Mike Sierra LLP | | 2006 |
| Mike Simpson Limited | Information & communication | 2023 |
| Mikeobile Solutions Ltd | Information & communication | 2025 |
| Mikey UK Vans Limited | Transport & logistics | 2026 |
| Mikeyg Boxing Limited | Arts & recreation | 2025 |
| Mikyle Ltd | Arts & recreation | 2025 |
| Mila Fruit & VEG Ltd | Wholesale & retail | 2025 |
| Milano A2Z Ltd | Transport & logistics | 2021 |
| Milbeth Limited | Wholesale & retail | 2023 |
| Mileash Property Services Limited | Real estate | 2022 |
| Miles Advisory LLP | | 2019 |
| Miles Advisory Services Limited | Professional & scientific | 2022 |
| Miles Management Limited | Professional & scientific | 2021 |
| Miles of Smiles Nursery Ltd | Health & social care | 2023 |
| Milestones Childcare Limited | Education | 2009 |
| Milfoil HC Ltd | Real estate | 2024 |
| Milifix Ltd | Construction | 2018 |
| Milion Ltd | Other services | 2020 |
| Militant Pancake Limited | Transport & logistics | 2019 |
| Military Comps Limited | Arts & recreation | 2023 |
| Miljam Properties Limited | Real estate | 1995 |
| Milk & Biscuits Ltd | Wholesale & retail | 2017 |
| Milk From the Hills Ltd | Manufacturing | 2024 |
| Mill DAM Limited | Professional & scientific | 2014 |
| Millclose Construction Limited | Construction | 2003 |
| Milldale Property Company Limited | Real estate | 1963 |
| Miller & Miller Surveyors Ltd | Real estate | 2015 |