| Menzies & Haddington Ltd | Construction | 2026 |
| Meomech Ltd | Professional & scientific | 2025 |
| MEP Pre-Construction Services Ltd | Construction | 2020 |
| Meraki Projects Ltd | Information & communication | 2018 |
| Merci Consulting Ltd | Professional & scientific | 2010 |
| Meridian (Motioneering) Limited | | 1986 |
| Merkandi Ltd | Wholesale & retail | 2015 |
| Merlin Fire Yorkshire Limited | Construction | 2023 |
| Merlin Transport Services Limited | Transport & logistics | 2024 |
| Merlin Trucks Limited | Wholesale & retail | 1994 |
| Merrit Commercial Structures Ltd | Construction | 2025 |
| Merrit Construction Ltd | Construction | 2024 |
| Merryweathers (Barnsley) Limited | Real estate | 2008 |
| Merryweathers (Doncaster) Limited | Real estate | 2008 |
| Merryweathers (Lettings) Limited | Real estate | 2008 |
| Merryweathers (Rotherham) Limited | Real estate | 2008 |
| Merryweathers Holdings Limited | Real estate | 2008 |
| Merryweathers Professional Services Limited | Real estate | 2008 |
| Merryweathers Sheffield Limited | Real estate | 2017 |
| Mesters Construction Ltd | Construction | 2023 |
| MET 1 Trading Limited | Water & waste | 2022 |
| MET QS & Estimating Ltd | Professional & scientific | 2025 |
| Meta Transport Limited | Transport & logistics | 2021 |
| Metalis Engineering Recruitment Limited | Administrative & support | 2019 |
| Metalis Recruitment Group Ltd | Administrative & support | 2026 |
| Metallix Refining Europe Ltd | Manufacturing | 2019 |
| Metalysis Holdings Limited | Manufacturing | 2021 |
| Metalysis International Ltd | Manufacturing | 2019 |
| Metalysis Ltd | Mining & quarrying | 2018 |
| Metalysis Services Ltd | Administrative & support | 2019 |
| Metamorpheus Ltd | Arts & recreation | 2013 |
| Metro Convenience Store Ltd | Wholesale & retail | 2024 |
| Metro Grocery Store Ltd | Wholesale & retail | 2025 |
| Metropolitan Cctv Limited | Administrative & support | 2019 |
| Mevis Ltd | Professional & scientific | 2018 |
| Mexborough TAP Limited | Hospitality | 2021 |
| Mexorad Ltd | Professional & scientific | 2024 |
| Meyra UK Ltd | Wholesale & retail | 2024 |
| MF Risen UK Limited | Wholesale & retail | 2026 |
| MFA Trading Ltd | Transport & logistics | 2025 |
| Mfgj Ltd | Hospitality | 2025 |
| MFU Bailiffs Limited | Administrative & support | 2003 |
| MG Helping Hands Ltd | Health & social care | 2022 |
| MG Marques Consulting Limited | Information & communication | 2014 |
| MG Property Swiss Ltd | Real estate | 2018 |
| MG Public Houses Ltd | Hospitality | 2025 |
| MG Traffic Solutions Ltd | Construction | 2019 |
| Mgb(Qc) Ltd | Construction | 2024 |
| MGK Transport Ltd | Transport & logistics | 2019 |
| MGR Technical Limited | Administrative & support | 2015 |
| MH Legal Solutions Ltd | Professional & scientific | 2018 |
| MHG Building Ltd | Construction | 2024 |
| MI Optics Ltd | Wholesale & retail | 2021 |
| MI Partitions Ltd | Construction | 2020 |
| MI Payments Ltd | Wholesale & retail | 2024 |
| Miaj Ltd | Wholesale & retail | 2016 |
| Michael a Jarvis & Co Ltd | Professional & scientific | 2019 |
| Michael George Commercials Limited | Wholesale & retail | 2007 |
| Michal Transport Ltd | Transport & logistics | 2016 |
| Mick Vials Angling Agencies Limited | Wholesale & retail | 2005 |
| Micks Coffee Shop Limited | Hospitality | 2025 |
| Microm UK Limited | Professional & scientific | 1992 |
| Midas Laser Ltd | Manufacturing | 2024 |
| Midnight Garage Ltd | Wholesale & retail | 2022 |
| Midson & Smith Limited | Real estate | 2013 |
| Mighalis Limited | Wholesale & retail | 2020 |
| Mighty Bull Transport Ltd | Wholesale & retail | 2024 |
| Mightybull Trucking Ltd | Wholesale & retail | 2025 |
| Mike Elliss Design Ltd | Professional & scientific | 2018 |
| Mikes Meters Ltd | Administrative & support | 2014 |
| Miklaszewski Ltd | Education | 2024 |
| MIL (Holdings) Limited | Professional & scientific | 2008 |
| Milburn (UK) Limited | Construction | 2007 |
| Millen Vision Limited | Hospitality | 2022 |
| Miller Groundworks & Landscaping Ltd | Construction | 2026 |
| Millers Motor Company Ltd | Wholesale & retail | 2017 |
| Millie's Floral Boutique Limited | Wholesale & retail | 2017 |
| Millies Cafe & Bakery Limited | Hospitality | 2026 |
| Millson Ford Ltd | Financial services | 2025 |
| Millstone Building Limited | Construction | 1994 |
| Millstone Inns Ltd | Hospitality | 2018 |
| Milltol Limited | Water & waste | 1989 |
| Milltown Consult Ltd | Construction | 2020 |
| Millward & Son's Ltd | Manufacturing | 2023 |
| Millward Lettings Ltd | Real estate | 2026 |
| Milnes and Sons Gardeners Ltd | Administrative & support | 2019 |
| Milpress Educational Limited | Professional & scientific | 2017 |
| Milton Street Dental Laboratory Limited | Health & social care | 2014 |
| Mimi ESA Ltd | Construction | 2023 |
| Mimic INK Ltd | Other services | 2026 |
| Mind & Emotions Psychology Ltd | Administrative & support | 2024 |
| Mind Body Investment Ltd | Information & communication | 2018 |
| Mindful Bytes Ltd | Information & communication | 2022 |
| Mindmesh Ltd | Information & communication | 2019 |
| Minds at Peace Foundation C.I.C. | Health & social care | 2023 |
| Mindsfull Ltd | Information & communication | 2020 |
| Minimelts & More 1 Ltd | Wholesale & retail | 2022 |
| Minimelts & More 2 Ltd | Wholesale & retail | 2022 |
| MIR Dental Limited | Health & social care | 2025 |
| MIR Project Management Limited | Professional & scientific | 2012 |