| Michael Davey Consulting Ltd | Information & communication | 2018 |
| Michael Peterson Limited | Wholesale & retail | 2008 |
| Michaelmas Properties Ltd | Real estate | 2026 |
| Michel Strauss Ltd | Professional & scientific | 2012 |
| Mick Butler & SON Ltd | Construction | 2011 |
| Mick MOY Tyres Ltd | Wholesale & retail | 2013 |
| Mick Walker Training Ltd | Professional & scientific | 2023 |
| Mickelburgh & Hunt Limited | Real estate | 2020 |
| Micro Data Systems Limited | Information & communication | 1989 |
| Micro Geotechnical Ltd | Professional & scientific | 2016 |
| Micro Holdings Ltd | Extraterritorial | 2023 |
| Micro Miniatures Ltd | Wholesale & retail | 2016 |
| Microcut Precision Engineering Limited | Manufacturing | 2002 |
| Microdots Services Ltd | Information & communication | 2026 |
| Micross Components Holdings Ltd | Professional & scientific | 2006 |
| Micross Components Limited | Manufacturing | 1984 |
| Micross UK Solutions Limited | Professional & scientific | 2013 |
| MID Devon Catering Limited | Hospitality | 2023 |
| MID Mist Properties Ltd | Real estate | 2023 |
| MID Norfolk 4X4 T/A Jacksons Car Sales Ltd | Wholesale & retail | 2005 |
| MID Norfolk Healthcare Limited | Health & social care | 2024 |
| MID Norfolk Home Improvements Ltd | Other services | 2019 |
| MID Norfolk Independent Practices Ltd | Professional & scientific | 2022 |
| MID Norfolk Utility Solutions Limited | Professional & scientific | 2013 |
| MID Suffolk Growth Ltd | Construction | 2019 |
| MID Suffolk Medical Supplies Limited | Wholesale & retail | 1997 |
| Mid-Shire Developments CD Limited | Construction | 2019 |
| Midas Gaming Limited | Arts & recreation | 2010 |
| Midas Miles Logistics Limited | Transport & logistics | 2021 |
| Midas Structural Ltd | Construction | 2011 |
| Midasnet Ltd | Information & communication | 2025 |
| Midcity Flooring Ltd | Construction | 2017 |
| Midday Studio Limited | Professional & scientific | 2013 |
| Middle Consulting Ltd | Professional & scientific | 2019 |
| Middleton & George Limited | Professional & scientific | 2004 |
| Middleton Farm Nurseries Limited | Administrative & support | 2003 |
| Middletons Lane Residents Association Limited | Households | 1995 |
| Midian Offshore Services Ltd | Professional & scientific | 2020 |
| Midile Ltd | Wholesale & retail | 2021 |
| Midis International Ltd | Mining & quarrying | 2024 |
| Midknight Design Ltd | Arts & recreation | 2021 |
| Midland Woodworking Co. Ltd | Wholesale & retail | 1926 |
| Midler Limited | Transport & logistics | 2022 |
| Midmist Alliance Ltd | Hospitality | 2023 |
| Midmist Munch Ltd | Hospitality | 2025 |
| Midstream Coatings Limited | Construction | 2003 |
| Mighty Green Direct Limited | Manufacturing | 2019 |
| Mighty Merchant Ltd | Wholesale & retail | 2018 |
| Mighty Oak Tree & Hedge Services Ltd | Administrative & support | 2025 |
| Mighty Step Media Ltd | Information & communication | 2024 |
| MIH Auto Ltd | Wholesale & retail | 2026 |
| Miha & Clau Ltd | Construction | 2017 |
| Mihail Ltd | Administrative & support | 2020 |
| Mihan Accounting Ltd | Professional & scientific | 2022 |
| Mikaz Limited | Administrative & support | 2014 |
| Mike Brudenell Limited | Education | 2005 |
| Mike Handley Aviation Services Ltd | Transport & logistics | 2018 |
| Mike Phillips Financials Limited | Financial services | 2013 |
| Mike, Debs & Sons Limited | Wholesale & retail | 2013 |
| Mikes Fish and Chips Ltd | Hospitality | 2018 |
| Mil-Tech Computer Systems Limited | Information & communication | 2006 |
| Mila's Home Foods Ltd | Hospitality | 2021 |
| Milaboo Ltd | Construction | 2026 |
| Milano AR Ltd | Other services | 2024 |
| Milburn Investment Group (MIG) Limited | Financial services | 2018 |
| Milburn Investment Properties Limited | Real estate | 2024 |
| Mild Panic Games Ltd | Information & communication | 2025 |
| Mile High Scaffolds Ltd | Construction | 2023 |
| Miles & Green Associates Limited | Health & social care | 2010 |
| Miles Bray Associates Ltd | Professional & scientific | 2016 |
| Miles Evans PR Limited | Administrative & support | 2017 |
| Miles Vehicle Deliveries Limited | Transport & logistics | 2002 |
| Milestone Atuo Parts Ltd | Wholesale & retail | 2025 |
| Milestone Impex Ltd | Wholesale & retail | 2025 |
| Milestone Therapy Centre Ltd | Health & social care | 2017 |
| Milex Auto Ltd | Wholesale & retail | 2026 |
| Milex Holdings Limited | Professional & scientific | 1993 |
| Milex Limited | Professional & scientific | 1992 |
| Milex Logistics Limited | Professional & scientific | 1999 |
| Mill Close (Poringland) Management Company Limited | Households | 2023 |
| Mill Corner Consultancy Ltd | Professional & scientific | 2025 |
| Mill Electrical Ltd | Construction | 2005 |
| Mill Green Services Limited | Construction | 2022 |
| Mill Hill Giles Limited | Financial services | 2014 |
| Mill House Partners 2012 Limited | Information & communication | 2009 |
| Mill Inn Spice Ltd | Hospitality | 2024 |
| Mill Reach Management Limited | Households | 2001 |
| Mill Road Services Limited | Construction | 2019 |
| Mill Street Auto Salvage Limited | Wholesale & retail | 2016 |
| Millan 25 Limited | Hospitality | 2024 |
| Millar Consulting Limited | Professional & scientific | 2022 |
| Millar Group Holdings Limited | Financial services | 2022 |
| Millar Lettings Limited | Real estate | 2019 |
| Millar West Holdings Limited | Financial services | 2016 |
| Millar West Limited | Wholesale & retail | 1998 |
| Millavon Limited | Wholesale & retail | 1975 |
| Millcroft Residents Management Company Limited | Households | 2004 |
| Millennial Motors Limited | Wholesale & retail | 2025 |
| Millennium Balti Limited | Hospitality | 2017 |
| Millennium Fresh Foods Ltd. | Extraterritorial | 1998 |