| Metro Industrial Limited | Real estate | 2026 |
| Metro Traffic Management Limited | Extraterritorial | 2026 |
| Metrowest Plumbing and GAS Services Ltd | Construction | 2016 |
| Mexcom Solutions Limited | Administrative & support | 2009 |
| MF Dobrica Transport Ltd | Transport & logistics | 2020 |
| MF Electrical (UK) Ltd | Construction | 2014 |
| MFR Services Ltd | Construction | 2022 |
| Mfuse Electrical and Cabling Limited | Construction | 2025 |
| MG Consult LDN Ltd | Professional & scientific | 2022 |
| Mgau Limited | Administrative & support | 2023 |
| MGM Building & Decorating Ltd | Construction | 2016 |
| MGR Investments Ltd | Real estate | 2006 |
| MH (Kent) Ltd | Hospitality | 2012 |
| MH 24/7 Fitness Ltd | Arts & recreation | 2022 |
| MHC Live in Care Ltd | Health & social care | 2023 |
| Mhpol Services Ltd | Transport & logistics | 2016 |
| MI Payroll & Bookkeeping Services Limited | Professional & scientific | 2017 |
| Miako Construction Ltd | Construction | 2025 |
| Micaab Services Limited | Information & communication | 2023 |
| Micalice Limited | Transport & logistics | 2023 |
| Micjeebs Ltd | Health & social care | 2023 |
| Mick Mccarthy Consulting Ltd | Health & social care | 2023 |
| Micorence Consulting Ltd | Administrative & support | 2015 |
| Microsilicon Group Ltd | Manufacturing | 2018 |
| Mida Consulting Limited | Health & social care | 2008 |
| Midas Bricks Ltd | Real estate | 2021 |
| Midas Flair Limited | Hospitality | 2019 |
| Middle ROW Property Limited | Real estate | 2023 |
| Migen Trans Limited | Transport & logistics | 2015 |
| Mihai Service Ltd | Transport & logistics | 2011 |
| Mihai-Florin Stan Ltd | Transport & logistics | 2026 |
| Mihails and SON Ltd | Transport & logistics | 2021 |
| Mihalcea Limited | Transport & logistics | 2014 |
| Mihmark Ltd | Transport & logistics | 2024 |
| Mihu Marketing Ltd | Professional & scientific | 2019 |
| Miiola Holdings Limited | Real estate | 2022 |
| Mike the Mecanic Ltd | Professional & scientific | 2017 |
| Mila FOY Ltd | Wholesale & retail | 2025 |
| Mila Property Holdings Ltd | Real estate | 2022 |
| Miles Accountancy Ltd | Professional & scientific | 2023 |
| Milestone Civils Ltd | Construction | 2015 |
| Milestone Events Limited | Hospitality | 2018 |
| Miletwelve Ltd | Information & communication | 2026 |
| Milkshake Management Limited | Arts & recreation | 2025 |
| Milla Trans Limited | Transport & logistics | 2017 |
| Millfield (Freehold) Limited | Households | 1996 |
| Millwright Mechanical Services Limited | Manufacturing | 2002 |
| Milton European Food Store Limited | Wholesale & retail | 2024 |
| Milton Grocery Ltd | Wholesale & retail | 2024 |
| Milton House (Bexley Lane) Management Limited | Households | 1998 |
| Milton Management Ltd | Professional & scientific | 1997 |
| Milton Place Limited | Households | 1996 |
| Milton Road Shisha Ltd | Wholesale & retail | 2025 |
| Milvic Construction Ltd | Construction | 2022 |
| Mimatt Consultancy Limited | Administrative & support | 2015 |
| Mimiloba Global Services Limited | Real estate | 2024 |
| Mimimiproperty Ltd | Real estate | 2024 |
| Mimshack Services Ltd | Professional & scientific | 2021 |
| Mindful Matters Counselling Limited | Extraterritorial | 2020 |
| Mindful Movement Studio Ltd | Arts & recreation | 2024 |
| Mindspring Diagnostics Ltd | Health & social care | 2022 |
| Mindtessori-Hub Ltd | Manufacturing | 2026 |
| Minenours Ltd | Health & social care | 2019 |
| Minervatech Limited | Professional & scientific | 2012 |
| Minimark Consulting Limited | Information & communication | 2016 |
| Ministry for Growth Limited | Professional & scientific | 2005 |
| Minmax Solutions Ltd | Wholesale & retail | 2009 |
| Mipo London Limited | Manufacturing | 2017 |
| Miracle Rosa Ltd | Other services | 2025 |
| Mirea Consultancy Ltd | Professional & scientific | 2024 |
| Mirea Transport Ltd | Transport & logistics | 2018 |
| Miriam Trans Ltd | Transport & logistics | 2025 |
| Miss Beauty Threading Bar Limited | Other services | 2017 |
| Misselbrooks Ltd | Professional & scientific | 2019 |
| Mit.Ace Ltd | Transport & logistics | 2022 |
| Mita IT Services Ltd | Information & communication | 2022 |
| Mitchell GEE Building Services Ltd | Professional & scientific | 2019 |
| Mitre Court(Belvedere)Management Co.Limited | Households | 1965 |
| Mixed Jelly Creative Ltd | Professional & scientific | 2019 |
| Mizizi Business Advisors Ltd | Professional & scientific | 2013 |
| Mjhr Estates Ltd | Real estate | 2026 |
| MJP Building Services Ltd | Construction | 2021 |
| Mjptranspartner Limited | Transport & logistics | 2025 |
| MK Fit Limited | Other services | 2024 |
| MK ICT Services Ltd | Education | 2011 |
| Mkeo Consultants Ltd | Professional & scientific | 2012 |
| MKG Mortgages Ltd | Financial services | 2023 |
| Mkhala Limited | Health & social care | 2024 |
| Mkhb Property Ltd | Real estate | 2024 |
| MKM Piskorski Limited | Construction | 2013 |
| MKS Scaffolding Limited | Construction | 2013 |
| Mkuodys Ltd | Transport & logistics | 2019 |
| ML Motorsport Ltd | Manufacturing | 2017 |
| MLS Festivals Limited | Arts & recreation | 2025 |
| MM Kuola Limited | Information & communication | 2006 |
| MMA Krav Maga Ltd. | Arts & recreation | 2013 |
| MMC Consulting Ltd | Construction | 2025 |
| MMG Sports and Arts Ltd | Wholesale & retail | 2020 |
| MMH Logistics Ltd | Transport & logistics | 2021 |
| MMM Pogi Ltd | Transport & logistics | 2017 |