| Midenn Properties Ltd | Real estate | 2025 |
| Midland Car Sales Ltd | Administrative & support | 2018 |
| Midland Property Estates Limited | Real estate | 2014 |
| Midland Road Hand Car Wash Ltd | Administrative & support | 2019 |
| Midland Shelving Limited | Construction | 2005 |
| Midland Trade Centre Limited | Wholesale & retail | 2008 |
| Midlands Invest Corporation Ltd | Real estate | 2025 |
| MIE Investments Limited | Real estate | 2024 |
| Miekha Limited | Health & social care | 2010 |
| Mierzejewski Trans Ltd | Transport & logistics | 2012 |
| Migo Trans Ltd | Transport & logistics | 2016 |
| Mihai Alin Limited | Transport & logistics | 2017 |
| Mihai Romeo Ltd | Transport & logistics | 2016 |
| Mihai&Construction Ltd | Construction | 2025 |
| Mihailitex Ltd | Wholesale & retail | 2022 |
| Mihaipatrick Ltd | Transport & logistics | 2021 |
| Mihlali Limited | Other services | 2014 |
| MII Furniture Ltd | Wholesale & retail | 2023 |
| MIK Courier Ltd | Transport & logistics | 2019 |
| Mika Services Ltd | Transport & logistics | 2018 |
| Mike & Sebastian Flex Ltd | Transport & logistics | 2023 |
| Mike DEE Ltd | Transport & logistics | 2021 |
| Mike Jarvis Landscaping & Fencing Ltd | Administrative & support | 2023 |
| Mike Smith Drums Limited | Arts & recreation | 2013 |
| MIKE24 Ltd | Transport & logistics | 2025 |
| Mikedoc Limited | Health & social care | 2015 |
| Miketel Data Networks Limited | Wholesale & retail | 2022 |
| Milan Unit Hair Design Limited | Other services | 2022 |
| Milberg Ltd | Professional & scientific | 2000 |
| Milborne Healthcare Limited | Health & social care | 2014 |
| Milc House Ltd | Hospitality | 2025 |
| Mildenhall Auto Care Centre Ltd | Other services | 2019 |
| Mile Recovery Ltd | Transport & logistics | 2024 |
| Mileni Ltd | Real estate | 2022 |
| Milerk Ltd | Wholesale & retail | 2020 |
| Miles Fire Protection Ltd | Construction | 2025 |
| Miles Portfolios Ltd | Construction | 2026 |
| Milestone Cars Limited | Wholesale & retail | 2009 |
| Milestones Florist Limited | Wholesale & retail | 2005 |
| Milhaan Metals Limited | Wholesale & retail | 2009 |
| Milking Equipment Association Limited | Other services | 2010 |
| Milkoo Ltd | Wholesale & retail | 2025 |
| Milky Pink Nails Ltd | Other services | 2026 |
| Milky TM Limited | Construction | 2026 |
| Mill House Studios Limited | Information & communication | 2020 |
| Mill Quay Moorings (ST. Ives) Limited | Households | 1998 |
| Mill Quay Residents Association (ST. Ives) Limited | Households | 1998 |
| Mill Street Homes Ltd | Construction | 2023 |
| Milldale Property Group Limited | Real estate | 2022 |
| Millen Properties Limited | Real estate | 2013 |
| Millennial Wealth Ltd | Financial services | 2018 |
| Millennium Industries Limited | Wholesale & retail | 1997 |
| Millennium Systems Services (UK) Ltd | Information & communication | 2005 |
| Millennium Tech Services Limited | Information & communication | 2017 |
| Millenniummotorgroup Ltd | Wholesale & retail | 2023 |
| Miller Martin Waste Services Ltd | Water & waste | 2023 |
| Millers Court Limited | Real estate | 2010 |
| Millfield Autoparts Limited | Wholesale & retail | 1999 |
| Millfield Convenience Store Ltd | Wholesale & retail | 2023 |
| Millfield Mobile Communications (UK) Ltd | Wholesale & retail | 2016 |
| Milli Enterprises Ltd | Wholesale & retail | 2020 |
| Millie & Co LLP | | 2002 |
| Millington DC Limited | Real estate | 2025 |
| Million Prints Limited | Manufacturing | 2025 |
| Millionaire Mastermind Limited | Administrative & support | 2023 |
| Millions Agency Limited | Professional & scientific | 2022 |
| Millolliam Limited | Administrative & support | 2024 |
| Millwaters Ltd | Administrative & support | 2019 |
| Millwood Holdings Limited | Administrative & support | 1971 |
| Millwood Properties (1994) Limited | Real estate | 2014 |
| Milly's Project Ltd | Manufacturing | 2021 |
| Milnyard Motors Ltd | Wholesale & retail | 2025 |
| Milo Transport Solutions Limited | Administrative & support | 2019 |
| Milton Freight Ltd | Transport & logistics | 2020 |
| Milton Property Group Limited | Real estate | 2023 |
| Milton(Peterborough)Estates Company, | Agriculture & fishing | 1934 |
| Milu Services Ltd | Administrative & support | 2017 |
| Mimea Mauzo Limited | Wholesale & retail | 2021 |
| Mimosil Technology Limited | Manufacturing | 1996 |
| Mimram Limited | Extraterritorial | 2022 |
| Mimram Special Works Limited | Construction | 2016 |
| Minaba Limited | Health & social care | 2015 |
| Minal Enterprises Ltd | Wholesale & retail | 2025 |
| Minbro Secretarial Services Limited | Administrative & support | 1988 |
| Mind Forge Hub Ltd | Professional & scientific | 2026 |
| Mind Your Performance Limited | Education | 2025 |
| Mindegl Ltd | Transport & logistics | 2018 |
| Minden GAS Services Ltd | Construction | 2025 |
| Mindtransport Ltd | Transport & logistics | 2024 |
| Mindway Health CIC | Health & social care | 2026 |
| Mineral Processing and Safety Limited | Wholesale & retail | 2007 |
| Minerva (PVT) Limited | Information & communication | 2012 |
| Minerva Vets Ltd | Professional & scientific | 2025 |
| Minggarden Oriental Ltd | Hospitality | 2026 |
| Mini Market T/A Town Shop Ltd | Wholesale & retail | 2024 |
| Minimal the Label Limited | Wholesale & retail | 2020 |
| Minime Entertainment Ltd | Information & communication | 2023 |
| Minimix (Peterborough) Ltd | Manufacturing | 2024 |
| Miniwest Ltd | Wholesale & retail | 2026 |
| Minnis Logistics Ltd | Extraterritorial | 2018 |