| Media 219 Limited | Information & communication | 2008 |
| Media Information Solutions Limited | Information & communication | 1997 |
| Media Trans Ltd | Transport & logistics | 2018 |
| Medical Aesthetics by Nina Ltd | Health & social care | 2022 |
| Medieval Chemistry Ltd | Arts & recreation | 2016 |
| Medy-Trans Ltd | Transport & logistics | 2014 |
| Meekz Music Lifestyle & Entertainment Ltd | Information & communication | 2019 |
| Meen Agri Services Limited | Agriculture & fishing | 2020 |
| Megan Rose Lane Ltd | Arts & recreation | 2019 |
| Melissa Sells Ltd | Wholesale & retail | 2025 |
| Melissa Trans Ltd | Transport & logistics | 2012 |
| Menny Paws Ltd | Administrative & support | 2025 |
| Mercury Lettings & Management Limited | Real estate | 2025 |
| Mercury Payroll Solutions Limited | Professional & scientific | 2023 |
| Meridian Action Group Ltd | Other services | 2024 |
| Merlin Polyurethane Limited | Manufacturing | 1996 |
| Merylite Ltd | Health & social care | 2025 |
| Mesud Ltd | Hospitality | 2024 |
| Metaphysiotherapy Ltd | Health & social care | 2022 |
| Methodix Limited | Information & communication | 2025 |
| MGA Transport Ltd | Wholesale & retail | 2006 |
| MGD Management Ltd | Administrative & support | 2013 |
| MGI Legal Ltd | Information & communication | 2022 |
| MGM Produce Limited | Wholesale & retail | 2013 |
| MGO Construction Management Limited | Construction | 2016 |
| MGW Logistics Ltd | Transport & logistics | 2015 |
| MH Property Maintenance (East) Ltd | Administrative & support | 2021 |
| MHM (UK) Ltd | Manufacturing | 2005 |
| Mia's Autos Ltd | Wholesale & retail | 2018 |
| Michael OKO Property Limited | Real estate | 2025 |
| Michael's Transport Limited | Transport & logistics | 2008 |
| Michail Ltd | Transport & logistics | 2019 |
| Mick Cawley Motor Engineer Ltd | Wholesale & retail | 2012 |
| Mick Cleaning Ltd | Administrative & support | 2026 |
| Mick Cunningham Spalding Ltd | Financial services | 2019 |
| Mickey Trans Limited | Transport & logistics | 2017 |
| Micutul Ltd | Administrative & support | 2018 |
| Midas Transport Limited | Transport & logistics | 1999 |
| Middledene Limited | Professional & scientific | 2002 |
| Midlands Roofing and Repairs Ltd | Construction | 2025 |
| Midnight Run Ltd | Transport & logistics | 2026 |
| Mietek Transport Limited | Transport & logistics | 2025 |
| Migrant Worker Management Ltd | Professional & scientific | 2025 |
| Mihtransltd Limited | Transport & logistics | 2018 |
| Mike Brooke Sports Therapy Ltd | Health & social care | 2026 |
| Mike Yould Developments Ltd | Construction | 2005 |
| Mike Yould Plumbing & Heating Ltd | Construction | 2005 |
| Mikla Service Ltd | Transport & logistics | 2015 |
| Miko Logistic Ltd | Transport & logistics | 2020 |
| Milana SB Ltd | Transport & logistics | 2023 |
| Milani Products Ltd | Wholesale & retail | 2025 |
| Milkshake Madness Ltd | Hospitality | 2019 |
| Mill House Farm Ltd | Agriculture & fishing | 2006 |
| Millsafe Associates Ltd | Professional & scientific | 2020 |
| Milnes Mortgages Limited | Financial services | 2024 |
| Milteq Ltd | Professional & scientific | 2026 |
| Miltine Mechanical + Electrical Ltd | Construction | 2023 |
| Milverton Rehab Publishing Ltd | Information & communication | 2025 |
| Mind and Motion Therapy Ltd | Wholesale & retail | 2015 |
| Mind Bicycle Ltd | Professional & scientific | 2023 |
| Mindeta Ltd | Transport & logistics | 2018 |
| Mindsons Ltd | Wholesale & retail | 2026 |
| Mine and Quarry Surveys Limited | Professional & scientific | 1991 |
| Mineral Coatings Limited | Manufacturing | 1998 |
| Minerva Business Consultancy Limited | Professional & scientific | 2024 |
| Minh TRI Ltd | Other services | 2025 |
| Mini Munchkins Ltd | Health & social care | 2023 |
| Mini Poli DA Ltd | Wholesale & retail | 2026 |
| Mini Poli Spalding Ltd | Wholesale & retail | 2016 |
| Minstrels Village Management Limited | Households | 2006 |
| Miruna 2016 Ltd | Transport & logistics | 2018 |
| Mirunatransport Ltd | Transport & logistics | 2015 |
| Miss Katie's Class Limited | Information & communication | 2025 |
| Missy Maison Ltd | Real estate | 2025 |
| Mitch-Tech Group Limited | Manufacturing | 2022 |
| Mitrache Limited | Transport & logistics | 2019 |
| MJ Retail Limited | Wholesale & retail | 2024 |
| MJ Sparkle Limited | Extraterritorial | 2017 |
| MJ Transport Ltd | Transport & logistics | 2025 |
| MJF Surfacing Ltd | Construction | 2018 |
| MJL Property & Holdings Ltd | Real estate | 1985 |
| MJL Restorations Ltd | Wholesale & retail | 2012 |
| MJL Skipmaster Limited | Manufacturing | 2000 |
| MJM Transport (Spalding) Limited | Transport & logistics | 2014 |
| MJP Coffee Limited | Wholesale & retail | 2025 |
| MJS Trading (Lincs) Ltd | Wholesale & retail | 2025 |
| MJW Carpentry Ltd | Construction | 2020 |
| MK Jobs Ltd | Transport & logistics | 2026 |
| MK Maintenance Northants Ltd | Construction | 2026 |
| MK Used Car Parts Ltd | Wholesale & retail | 2026 |
| Mkhela Ltd | Health & social care | 2023 |
| MKN Driver Ltd | Transport & logistics | 2019 |
| MKN Trans Ltd | Transport & logistics | 2017 |
| ML Fleet Services Ltd | Wholesale & retail | 2023 |
| ML Motors (Eastern) Ltd | Wholesale & retail | 2022 |
| MLH Investments Ltd | Financial services | 2024 |
| MLK Trading Ltd | Transport & logistics | 2026 |
| MM Barbers Ltd | Other services | 2025 |
| MM MAT Trans Ltd | Transport & logistics | 2026 |
| MMB Developments (Lincs) Limited | Real estate | 2025 |