| Lteam Limited | Administrative & support | 2020 |
| Lufin Associates Limited | Professional & scientific | 2016 |
| Luke Wellock Sustainability Ltd | Professional & scientific | 2023 |
| Lund Group Limited | Construction | 2010 |
| Luxeworld Realty Limited | Real estate | 2025 |
| Luxor Developments Ltd | Construction | 2018 |
| Luxury Train Club Ltd | Administrative & support | 2024 |
| Lymond Properties Ltd | Real estate | 2018 |
| LZK Property Ltd | Real estate | 2022 |
| Löyly & JÄÄ Sauna Limited | Arts & recreation | 2023 |
| M B Clarkson Ltd | Professional & scientific | 2023 |
| M F Handbags Ltd | Wholesale & retail | 2007 |
| M R Building & Roofing Ltd | Construction | 2020 |
| M&E Prenga Property Limited | Real estate | 2022 |
| M. J. F. Leisure Limited | Arts & recreation | 2007 |
| M.C.C. (Burley in Wharfedale) Ltd | Wholesale & retail | 2006 |
| M.J. Hodgson Limited | Administrative & support | 2002 |
| M.R. Sewing Machines Ltd | Manufacturing | 2023 |
| MAC Surgical Limited | Health & social care | 2025 |
| Macar Ltd | Information & communication | 2023 |
| Macara Accountancy Ltd | Professional & scientific | 2021 |
| Macara Accountants Ltd | Professional & scientific | 2024 |
| Macara Ltd | Professional & scientific | 2026 |
| Macca Homes Limited | Real estate | 2021 |
| Macgregor Property Management Ltd | Real estate | 2018 |
| Mags Worldwide Limited | Administrative & support | 1999 |
| Mainone Project Management and Consultancy Limited | Professional & scientific | 2022 |
| Maison Avlo Limited | Real estate | 2025 |
| Making Choices Limited | Professional & scientific | 2003 |
| MAM Properties Ltd | Real estate | 2012 |
| Mammoth Digital Solutions Ltd | Professional & scientific | 2021 |
| Mandate Solutions Limited | Administrative & support | 2013 |
| Mann Joinery Limited | Construction | 2011 |
| Manny Steak House Ltd | Hospitality | 2019 |
| Manor Court Yeadon (1) Limited | Households | 1986 |
| Manor House Management (Pool) Limited | Households | 1988 |
| Mapacare Limited | Professional & scientific | 2014 |
| Mara Estates Limited | Real estate | 2010 |
| Mara Property Partners Ltd | Real estate | 2025 |
| Marchinton Consulting Limited | Administrative & support | 2024 |
| Mark Griffin Associates Ltd | Administrative & support | 2020 |
| Mark Hindmarsh Technical Consulting Limited | Information & communication | 2001 |
| Mark Laurence LEA Limited | Extraterritorial | 2025 |
| Mark Mckenzie Hairdressing Ltd | Arts & recreation | 2025 |
| Mark Whittington Developments Ltd | Real estate | 2018 |
| Mark Whittington Ltd | Construction | 2014 |
| Marshall (Teesside) Ltd | Wholesale & retail | 2015 |
| Martin Higgitt Associates Limited | Professional & scientific | 2017 |
| Martin's Pubs, Clubs & Restaurants Ltd | Hospitality | 2018 |
| Maryland House (Leeds) Management Company Limited | Households | 2001 |
| Matchbox Ltd | Professional & scientific | 2026 |
| Materia Prima Limited | Education | 2025 |
| Matter Communications Limited | Professional & scientific | 2009 |
| Matthew Snow Advisory Limited | Professional & scientific | 2015 |
| Matthysen LLC Ltd | Real estate | 2025 |
| Mauve Idea Limited | Information & communication | 2007 |
| Maximis Limited | Information & communication | 2011 |
| Maxus York Limited | Wholesale & retail | 2019 |
| Maxwells Restaurants Limited | Hospitality | 1972 |
| Mayfair Sheffield Limited | Real estate | 2003 |
| Maynards Europe Ltd | Wholesale & retail | 2020 |
| Maze Moments Ltd. | Wholesale & retail | 2024 |
| MB60 Ltd | Other services | 2026 |
| MBT Investments (Holdings) Limited | Financial services | 2023 |
| MC Tiling Limited | Construction | 2014 |
| Mccash Limited | Professional & scientific | 2016 |
| Mccaul Developments Limited | Real estate | 2005 |
| Mccauley and Co Limited | Administrative & support | 2011 |
| Mccreery-Phillips Ltd | Real estate | 2016 |
| Mcdowell Property Ltd | Real estate | 2023 |
| Mcglynn Investments Ltd | Real estate | 2021 |
| Mcgovan Plumbing Limited | Construction | 2006 |
| Mcharmedia Limited | Professional & scientific | 2020 |
| Mckendrick Estates Limited | Real estate | 2015 |
| Mcla Ltd | Transport & logistics | 2018 |
| Mclanee Europe Ltd | Wholesale & retail | 2024 |
| MCQ Partnership Limited | Administrative & support | 2021 |
| MD Projects Management Limited | Construction | 2019 |
| MDK Outsourcing Solutions Ltd | Professional & scientific | 2020 |
| MDY Project Management Ltd | Real estate | 2010 |
| Medea S J Limited | Real estate | 2024 |
| Medgene Technologies Ltd | Professional & scientific | 2023 |
| Meer Projects Ltd | Construction | 2018 |
| Meera Enterprise Limited | Wholesale & retail | 2008 |
| Mekts Properties Ltd | Real estate | 2025 |
| Meldrin Ventures Ltd | Real estate | 2024 |
| Melrose Place Limited | Real estate | 2017 |
| Melvyn Thorpe Southfield Court (Flats Management) Limited | Households | 1978 |
| Memo Developments Ltd | Real estate | 2018 |
| Mena Advisory Ltd | Professional & scientific | 2025 |
| Menston Hall Management Company Limited | Households | 2010 |
| Menston Post OFF Ltd | Transport & logistics | 2026 |
| Menston Spice Limited | Hospitality | 2019 |
| Mercury Bidco Limited | Administrative & support | 2019 |
| Mercury LEV Ltd | Administrative & support | 2023 |
| Meridien Construction Limited | Construction | 2007 |
| Meridien Homes Limited | Construction | 2011 |
| Metsmatics Limited | Real estate | 1961 |
| MG Hendron Consultancy Ltd | Wholesale & retail | 2025 |
| MG RAM 66 Engineering Ltd | Professional & scientific | 2018 |