| Merchant Millers Ltd | Manufacturing | 2024 |
| Merchant Services Experts Ltd | Financial services | 2021 |
| Mercia Building Services Ltd | Construction | 2019 |
| Merelina Ltd | Wholesale & retail | 2025 |
| Meridian Business Planning Accountancy and Tax Ltd | Professional & scientific | 2019 |
| Meridian Cafe Cleethorpes Limited | Hospitality | 2025 |
| Meridian Moments CIC | Health & social care | 2024 |
| Mersey Trading Limited | Information & communication | 2017 |
| MES Engineering Ltd | Construction | 2017 |
| Meter Room | Arts & recreation | 2011 |
| MF (SA) Ltd | Wholesale & retail | 2020 |
| MF Office Solutions Ltd | Construction | 2015 |
| MFV Solstice II Limited | | 2002 |
| MG Offshore Services Ltd | Administrative & support | 2025 |
| MG Site Solutions Limited | Construction | 2018 |
| MG Steel Erection Ltd | Construction | 2012 |
| MG Transport Ltd | Transport & logistics | 2014 |
| MGB Basketball Ltd | Arts & recreation | 2026 |
| Mgc-Trans Ltd | Transport & logistics | 2016 |
| MGN Scaffolding Limited | Construction | 2018 |
| MH Courier Services Ltd | Transport & logistics | 2020 |
| MH Mechanical Ltd | Professional & scientific | 2026 |
| Mhrl Limited | Wholesale & retail | 2006 |
| Miava Limited | Other services | 2019 |
| Michael Bass Grimsby Limited | Construction | 2002 |
| Michael Carr Consultancy Limited | Administrative & support | 2008 |
| Michael Culshaw & Co Limited | Professional & scientific | 2007 |
| Michael Hodges Bricklaying Limited | Construction | 2019 |
| Michael Knowles Works Limited | Administrative & support | 2018 |
| Michelle P Cleaning Services Ltd | Administrative & support | 2024 |
| Mick Henry Plumbing & Heating Engineers Ltd | Construction | 2003 |
| Microbit Engineering Limited | Professional & scientific | 2019 |
| Microwave Games Ltd | Information & communication | 2026 |
| MID Atlantic Hedges Limited | Health & social care | 2021 |
| Midas Civil Ltd | Construction | 2025 |
| Middleton Clarke Ltd | Construction | 2011 |
| Middleton's Glass Limited | Manufacturing | 2006 |
| Midgg Limited | Information & communication | 2024 |
| Midland Service Garage Limited | Wholesale & retail | 2020 |
| Mighty Mariners Boxing Academy CIC | Education | 2020 |
| Mika Transport Ltd | Transport & logistics | 2023 |
| Mike Burton's Positive Messages Ltd | Professional & scientific | 2024 |
| Mike Freer Plumbing & Heating Services Ltd | Construction | 2009 |
| Mike Lawton Associates Ltd | Professional & scientific | 2019 |
| Mil's Melts Limited | Wholesale & retail | 2022 |
| Milabunk Ltd | Wholesale & retail | 2018 |
| Milanos Pizza Grimsby Limited | Real estate | 2012 |
| Milanos Pizza Kebab House Ltd | Hospitality | 2026 |
| Milchester House Limited | Financial services | 2025 |
| Milestone Finance Limited | Other services | 2009 |
| Millarsmarvels Ltd | Wholesale & retail | 2015 |
| Millennium Inorganic Chemicals Overseas Holdings | Financial services | 1989 |
| Millennium Nails Limited | Wholesale & retail | 1998 |
| Miller & Thompson Properties Ltd | Real estate | 2024 |
| Millerstaxi.Com Limited | Transport & logistics | 2010 |
| Millies Melts Ltd | Wholesale & retail | 2025 |
| Millstone Garden Centre Limited | Wholesale & retail | 2025 |
| Milsim Supplies Ltd | Wholesale & retail | 2023 |
| Milson Services Limited | Construction | 2019 |
| Milsons Holdings Ltd | Real estate | 2025 |
| Milthorp Plumbing & Heating Ltd | Construction | 2024 |
| Milton Anzie Holdings LLP | | 2019 |
| Milton Anzie Two Limited | Real estate | 2022 |
| Mind Merchant Limited | Other services | 2024 |
| Mindcast Ltd | Information & communication | 2022 |
| Mindset Learning Group Limited | Education | 2026 |
| Mini European Market Ltd | Wholesale & retail | 2022 |
| Minor Oral Surgery Ltd | Health & social care | 2015 |
| Mintik Limited | Real estate | 2013 |
| Minting Holdings Ltd | Administrative & support | 2019 |
| Mintleaf Ltd | Hospitality | 2017 |
| Minus Three Degrees Limited | Hospitality | 2018 |
| Mirea Transport Logistic Ltd | Transport & logistics | 2025 |
| Miregen Capital Ltd | Financial services | 2023 |
| Mirracare Limited | Construction | 2002 |
| Mirus Machine Services Limited | Manufacturing | 2018 |
| Miss MKB Ltd | Professional & scientific | 2025 |
| Mitchells & SON Damp Proofing Services Ltd Limited | Construction | 2026 |
| Miva Mids Limited | Professional & scientific | 2023 |
| MJ & a Accountancy and Stocktaking Services Limited | Professional & scientific | 2005 |
| MJ Matten Limited | Hospitality | 2019 |
| MJ Properties Lincs Ltd | Real estate | 2025 |
| MJ Tyre Services Limited | Wholesale & retail | 2019 |
| MJB Facilities Ltd | Construction | 2017 |
| MJC Holdings 2025 Limited | Financial services | 2025 |
| MJD Gardening and Landscape Limited | Administrative & support | 2022 |
| Mjdbd Transport Services Limited | Transport & logistics | 2014 |
| Mjec Property Limited | Real estate | 2016 |
| MJM Gateway Limited | Administrative & support | 2026 |
| Mjph Joinery Limited | Construction | 2015 |
| MK Aujla Group Ltd | Real estate | 2021 |
| MK Aujla II Ltd | Households | 2019 |
| MK Aujla Ltd | Real estate | 2016 |
| MK Top Transport Ltd | Transport & logistics | 2013 |
| MK Total Engineering Solutions Ltd | Professional & scientific | 2025 |
| MKG Wealth Management Limited | Financial services | 2025 |
| ML Consultancy Ltd | Professional & scientific | 2021 |
| MLA Design and Build Limited | Construction | 2019 |
| Mlbb NN Ltd | Transport & logistics | 2025 |
| MLR Administration Services Limited | Administrative & support | 2011 |