| Michael Thorne Consulting Limited | Professional & scientific | 2014 |
| Michelle Breslin Limited | Wholesale & retail | 2024 |
| Mickey Lowe Films Limited | Information & communication | 2015 |
| Micro Design & Engineering Services Limited | Construction | 1995 |
| Midcroft House (Tring) Management Limited | Households | 2005 |
| Mighty Bite Kebab Ltd | Hospitality | 2025 |
| Mill House Associates Limited | Professional & scientific | 2022 |
| Millbrook Electronics Ltd | Manufacturing | 2024 |
| Millers Park Management Company Limited | Households | 2008 |
| Millhoppers Group Ltd | Transport & logistics | 2026 |
| Mills Paints Limited | Wholesale & retail | 2014 |
| Milton Keynes Builders Limited | Extraterritorial | 2014 |
| Minerva Education Consultancy Ltd | Education | 2017 |
| Minerva Support Limited | Arts & recreation | 2010 |
| Ming Stove Ltd | Hospitality | 2022 |
| Mini Monster Stunts Limited | Information & communication | 2021 |
| Minka London Ltd | Professional & scientific | 2013 |
| Mint Digital Consultancy Ltd | Information & communication | 2022 |
| Miraniya Consultancy Ltd | Professional & scientific | 2025 |
| Mirflow Ltd | Professional & scientific | 2026 |
| Miro Infrastructure Ltd | Construction | 2026 |
| Mitt Limited | Professional & scientific | 2024 |
| MJM Property Group Ltd | Real estate | 2024 |
| MK Construction and Groundwork Limited | Construction | 2026 |
| MKA Contracting Ltd | Professional & scientific | 2024 |
| MKG Property Limited | Real estate | 2018 |
| Mleuk Ltd | Extraterritorial | 2017 |
| MM Design Engineering Ltd | Professional & scientific | 2020 |
| Mmat Limited | Financial services | 2024 |
| Mmcc Ltd | Information & communication | 2023 |
| Mofohifi Records Limited | Information & communication | 2006 |
| MOH Tech Services Ltd | Information & communication | 2023 |
| Monavis Ltd | Professional & scientific | 2023 |
| Mond Contemporary Ltd | Arts & recreation | 2025 |
| Mondays Occupational Psychologists Limited | Education | 2007 |
| Mono Technology Limited | Information & communication | 2018 |
| Moorhouse Pallets Limited | Manufacturing | 2022 |
| Moral Fibre Food Ltd | Manufacturing | 2012 |
| More Flowers Less Drama Ltd | Wholesale & retail | 2023 |
| More Tars Investments Ltd | Real estate | 2019 |
| More Than Pixels Ltd | Information & communication | 2024 |
| Morgan Retail Services Limited | Hospitality | 2016 |
| Morley IT Limited | Information & communication | 2023 |
| Most Contentious Limited | Professional & scientific | 2024 |
| Mother Cuppa Tea Ltd | Manufacturing | 2022 |
| Mount Design Limited | Professional & scientific | 2018 |
| Mountaincreek Limited | Professional & scientific | 2014 |
| Movement Bliss Limited | Health & social care | 2008 |
| MP Design & Build Ltd | Construction | 2024 |
| Mpep Consulting Limited | Professional & scientific | 2024 |
| Mpfe Consultancy Ltd | Information & communication | 2018 |
| MPG Complete Construction Ltd. | Construction | 2012 |
| MPR Groundworks Ltd | Extraterritorial | 2017 |
| Mpsa Consultancy Limited | Information & communication | 2008 |
| MR SIB Ltd | Administrative & support | 2019 |
| MRK Talent Solutions Ltd | Administrative & support | 2025 |
| MRW Group Servicing Ltd | Financial services | 2023 |
| MS Aerospace Ltd | Professional & scientific | 2024 |
| Ms&E Limited | Real estate | 2025 |
| Ms&N Ltd | Wholesale & retail | 2018 |
| Mscm Subsea Solutions Ltd | Manufacturing | 2015 |
| MSK Practitioner Ltd | Health & social care | 2024 |
| Mumbloom Ltd | Wholesale & retail | 2026 |
| Musa-Uk Ltd | Hospitality | 2024 |
| Musclesmith Ltd | Other services | 2024 |
| Music, Marketing & Media Ltd | Information & communication | 2020 |
| N & G Autos Limited | Wholesale & retail | 2014 |
| NAD Consultants Ltd. | Administrative & support | 2014 |
| Nakatomi Corporation Limited | Information & communication | 2015 |
| Namastow Ltd | Professional & scientific | 2019 |
| Nasser Corp Ltd | Information & communication | 2024 |
| Natalie Lynn Ltd | Professional & scientific | 2021 |
| Nately Research Ltd | Information & communication | 2023 |
| Natural Colours Limited | Extraterritorial | 1995 |
| Nazary Properties Ltd | Real estate | 2023 |
| NBA Consulting Ltd | Administrative & support | 2023 |
| NC4T Ltd | Professional & scientific | 2017 |
| NCL Rail Ltd | Professional & scientific | 2026 |
| Nemesis Events Ltd | Arts & recreation | 2026 |
| Neritic Ltd | Information & communication | 2017 |
| Netquest Consulting Limited | Other services | 2002 |
| Neutral Host Networks CIC | Information & communication | 2023 |
| Nextwave Programmes Ltd | Professional & scientific | 2025 |
| NH Autos Limited | Wholesale & retail | 2015 |
| Niblicks Consultancy Limited | Professional & scientific | 2010 |
| NIC Construction Ltd | Construction | 2026 |
| Nightip Networks Limited | Information & communication | 2010 |
| Nikodax Limited | Information & communication | 2018 |
| Nikon X-Tek Systems Limited | Manufacturing | 1986 |
| Nile Spring Limited | Information & communication | 2019 |
| NJB Consultancy Services Limited | Professional & scientific | 2018 |
| NJB Video Limited | Information & communication | 2015 |
| NJS Embedded Systems & Control Limited | Professional & scientific | 2022 |
| Nkwellness Ltd | Health & social care | 2025 |
| NO Wood Gets Wasted Ltd | Construction | 2024 |
| Noble Endeavours Ltd | Professional & scientific | 2023 |
| Noble Foods (WE) Limited | Energy | 1991 |
| Noble Pullet Finance Limited | Financial services | 2013 |
| NOI Dining Ltd. | Hospitality | 2018 |
| Nomadic Spirits Collective Ltd | Professional & scientific | 2021 |