| M.R Autos Vehicle Maintenence Ltd | Wholesale & retail | 2024 |
| M.R.F. Medics Limited | Health & social care | 2022 |
| M.W.I Electrical Limited | Professional & scientific | 2016 |
| M12 Global Limited | Financial services | 2018 |
| M2 (Bristol) Ltd | Construction | 2023 |
| M2 Project Management & Building Services Limited | Construction | 2014 |
| M25 Motors Limited | Wholesale & retail | 2017 |
| M2Z Property Limited | Real estate | 2025 |
| M3 Corporate Finance LLP | | 2007 |
| M32 Security Limited | Administrative & support | 2025 |
| M4 Law Limited | Administrative & support | 2024 |
| M4 Property Limited | Real estate | 2018 |
| M4M QS Limited | Professional & scientific | 2005 |
| M5 Real Estate Limited | Real estate | 2025 |
| M5 Scaffolding Ltd | Construction | 2025 |
| M5 Security Services Ltd | Administrative & support | 2019 |
| M6MAJOR.COM Management Company Limited | Real estate | 2018 |
| M:Mck Ltd | Health & social care | 2025 |
| M<<Corporation Ltd. | Manufacturing | 2025 |
| MA (A&T) Services Limited | Professional & scientific | 2015 |
| MA Accounting & Tax Services Limited | Extraterritorial | 2025 |
| MA Estates Group Limited | Real estate | 2026 |
| MA Global Investments Limited | Extraterritorial | 2012 |
| MA Guardian Company Limited | Professional & scientific | 2011 |
| MA Services Bristol Ltd | Wholesale & retail | 2023 |
| MA1DISTRIBUTORS Ltd | Wholesale & retail | 2025 |
| MA3T Ltd | Wholesale & retail | 2015 |
| MAA Lokkhi Properties Ltd | Real estate | 2020 |
| MAA Shakti Trading Ltd | Wholesale & retail | 2026 |
| Maab and Co Ltd | Hospitality | 2014 |
| Maalhub Accounting Services Limited | Professional & scientific | 2026 |
| Maandeeq Centre Ltd | Real estate | 2022 |
| Maars Living Walls UK Ltd | Construction | 2021 |
| Maas Logistics Ltd | Transport & logistics | 2015 |
| MAB Design Consultancy Ltd | Administrative & support | 2025 |
| MAB Maintenance Specialist Limited | Other services | 2024 |
| MAB Solutions (UK) Ltd | Professional & scientific | 2012 |
| Maba Developments Ltd | Real estate | 2025 |
| Mabat Limited | Education | 2009 |
| Mabboo Limited | Wholesale & retail | 2008 |
| Mabella Limited | Health & social care | 2023 |
| MAC Accounting Ltd | Professional & scientific | 2020 |
| MAC Build Bros Ltd | Construction | 2019 |
| MAC Ceramics Ltd | Construction | 2018 |
| MAC Donnell Limited | Professional & scientific | 2012 |
| MAC Nelson Ltd. | Information & communication | 2023 |
| MAC New Consulting Limited | Professional & scientific | 2023 |
| MAC Utilities Limited | Construction | 2021 |
| Mac-Cnc Limited | Manufacturing | 2025 |
| Mac-Tech Solutions Limited | Information & communication | 2005 |
| Macaronesia Consulting Ltd | Professional & scientific | 2016 |
| Macaroon Associates Limited | Information & communication | 2017 |
| Macarthur Wilson Ltd | Administrative & support | 1999 |
| Macatax Limited | Professional & scientific | 2006 |
| Macdonald Dona Lola NO. 14 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO. 15 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO. 21 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO. 4 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO. 5 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO. 9 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO.16 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO.17 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO.18 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO.19 Limited | Professional & scientific | 1987 |
| Macdonald Dona Lola NO.20 Limited | Professional & scientific | 1987 |
| Macdonald Russell Limited | Real estate | 2010 |
| Mace & Menter Ltd | Information & communication | 2012 |
| Mace Construct Services Limited | Construction | 2026 |
| Mace Construction Management Ltd | Extraterritorial | 2026 |
| Macegreen Consulting Limited | Professional & scientific | 2011 |
| Macfarlane Investments Ltd | Real estate | 2019 |
| Macfarlane Investments Two Ltd | Real estate | 2022 |
| Macferson Ltd | Professional & scientific | 2020 |
| Macfind Limited | Professional & scientific | 1989 |
| Mach Acoustics Limited | Professional & scientific | 2003 |
| Mach D Trading Ltd | Information & communication | 2023 |
| Mach Machine Tools Limited | Wholesale & retail | 2013 |
| Mach Vintage Ltd | Wholesale & retail | 2025 |
| Macharia and Sons Limited | Health & social care | 2018 |
| Machin Court Management Company Limited | Extraterritorial | 2009 |
| Machine Repairs Ltd | Manufacturing | 2025 |
| Machine Tool Sales Online Limited | Extraterritorial | 2010 |
| Machine Toolery Limited | Wholesale & retail | 2025 |
| MACHINE137 Limited | Information & communication | 2023 |
| Machineria Romana Britania Ltd | Manufacturing | 2025 |
| Machinery Matters Ltd | Administrative & support | 2025 |
| Machins Mews Management Company Limited | Households | 2006 |
| Mack Beauty Limited | Other services | 2015 |
| Mack Daddys North Street Limited | Other services | 2012 |
| Mack Daddys Westbury Park Limited | Other services | 2007 |
| Mack Group Limited | Administrative & support | 2015 |
| Mack Housing Development Limited | Construction | 2023 |
| Mack R Property Ltd | Real estate | 2024 |
| Mack Utilities Ltd | Construction | 2019 |
| Mackay Adventure Consultants Limited | Administrative & support | 2011 |
| Mackay and Sawyer Limited | Real estate | 2016 |
| Mackay Huxham Partnership Ltd | Construction | 2023 |
| Mackay Thomas Associates Ltd | Professional & scientific | 2010 |
| Mackean Lettings Limited | Real estate | 2023 |
| Mackendrick Norcott Limited | Real estate | 1978 |