| Move IT Recovery Limited | Transport & logistics | 2025 |
| Moving Digital Limited | Information & communication | 2024 |
| MP Electrical Solutions Ltd | Construction | 2025 |
| MPD Solutions Ltd | Professional & scientific | 2020 |
| MPG Building Services Ltd | Construction | 2007 |
| MPK Plastering and Rendering Ltd | Construction | 2021 |
| MPS Commercial Management Limited | Construction | 2012 |
| MQA Technologies Ltd | Information & communication | 2016 |
| MR Property Portsmouth Ltd | Real estate | 2020 |
| MR TEE Removals Services Ltd | Transport & logistics | 2019 |
| Mradafm Ltd | Health & social care | 2026 |
| Mreh Ltd | Health & social care | 2019 |
| MRG Effitas Limited | Administrative & support | 2016 |
| MRH PUB Company Limited | Hospitality | 2021 |
| MRL Installations Limited | Construction | 2006 |
| Mrlong Ltd | Hospitality | 2019 |
| MRN Electrical Services Ltd | Construction | 2023 |
| MS Creative Media Limited | Financial services | 2024 |
| MS Funfairs Ltd | Arts & recreation | 2025 |
| MS Khan Enterprises Ltd | Manufacturing | 2026 |
| MS Logit Ltd | Administrative & support | 2016 |
| MSB Property Consultancy Ltd | Real estate | 2019 |
| MSD Properties Limited | Real estate | 2014 |
| Msjw Properties Limited | Real estate | 2021 |
| MSK Cleaning Solutions Limited | Transport & logistics | 2024 |
| MSL Recruitment Ltd | Administrative & support | 2015 |
| Msquared South Ltd | Construction | 2022 |
| MST UK Holdings Ltd | Professional & scientific | 2024 |
| Mstm Developments Limited | Professional & scientific | 2003 |
| MT Mechanical and Electrical Services Limited | Manufacturing | 2007 |
| MTC Online Ltd | Wholesale & retail | 2025 |
| Mtec Property Ltd | Real estate | 2014 |
| Mtek Paving & Groundwork Specialists Ltd | Construction | 2023 |
| MTK Electrical Services Ltd | Administrative & support | 2019 |
| MTL Software Ltd | Information & communication | 2023 |
| MTS Medical Limited | Health & social care | 2026 |
| MU Property Facilities Limited | Construction | 2012 |
| Mubuz Vision Ltd | Information & communication | 2026 |
| Muchie Limited | Health & social care | 2018 |
| Mucworx Limited | Construction | 2024 |
| Mufarowashe Ltd. | Health & social care | 2016 |
| Muir Libations Ltd | Hospitality | 2022 |
| Mulberry Court PRE School Limited | Education | 2018 |
| Multihull International Limited | Wholesale & retail | 1992 |
| Multiples UK. Ltd | Transport & logistics | 2025 |
| Mumbles Health Limited | Health & social care | 2023 |
| Mumms Lounge Ltd | Hospitality | 2026 |
| Munchies Kitchen Bournemouth Limited | Hospitality | 2022 |
| Munchies Kitchen Croydon Ltd | Hospitality | 2024 |
| Munchies Kitchen Limited | Hospitality | 2014 |
| Munchies Kitchen Salisbury Limited | Hospitality | 2022 |
| Munchies Kitchen Winchester Limited | Hospitality | 2022 |
| Munchus Balloon Limited | Health & social care | 2019 |
| Mundo Care Limited | Health & social care | 2010 |
| Museotechniki Ltd | Wholesale & retail | 2015 |
| Muslim Ameer Ltd | Professional & scientific | 2022 |
| Muslimah Hearts Limited | Arts & recreation | 2026 |
| Musoni (PVT) Limited | Health & social care | 2014 |
| Musselwhite Photography Limited | Professional & scientific | 2014 |
| Mutero Limited | Health & social care | 2025 |
| Muthjane Limited | Health & social care | 2022 |
| Mutual Associates Limited | Real estate | 1987 |
| Mutual Services (Portsmouth) Limited | Other services | 2006 |
| MVF Solutions Limited | Administrative & support | 2025 |
| MVM Events Limited | Administrative & support | 2023 |
| MVP Design Ltd | Manufacturing | 2019 |
| MW Hampshire Ltd | Construction | 2026 |
| Mwaka Company Limited | Health & social care | 2011 |
| Mwjroy Limited | Administrative & support | 2015 |
| MWV Aviation Limited | Administrative & support | 2007 |
| My Fruitful Fingers Limited | Administrative & support | 2016 |
| My Mobile Tech Ltd | Wholesale & retail | 2023 |
| My-Direction Ltd | Health & social care | 2014 |
| Myaccountantuk Ltd | Professional & scientific | 2016 |
| Myatts Management Limited | Financial services | 2012 |
| Mybestfriendsfriends Ltd | Professional & scientific | 2025 |
| Myelae Limited | Hospitality | 2025 |
| Mynt Image Ltd | Administrative & support | 2013 |
| Myomb Limited | Professional & scientific | 2020 |
| Myriam Coupard Advisory Limited | Professional & scientific | 2020 |
| Mysl Limited | Hospitality | 2024 |
| Mysolvo Contracts Limited | Extraterritorial | 2017 |
| Mysolvo Limited | Administrative & support | 2014 |
| Mywebtonet Webhosting Ltd | Information & communication | 2012 |
| MZ Accountancy & Bookkeeping Services Ltd | Professional & scientific | 2024 |
| N & D Padbury Limited | Agriculture & fishing | 2020 |
| N & V Associates Ltd | Real estate | 2014 |
| N Cube B Limited | Real estate | 2018 |
| N Idris Solutions Limited | Professional & scientific | 2014 |
| N J Elite Goalkeeper Academy Ltd | Education | 2025 |
| N&L Couriers Ltd | Transport & logistics | 2020 |
| N-Viro Limited | Administrative & support | 1995 |
| N.E.G. Windows and Property Services Limited | Construction | 2018 |
| N.P. Brown Consulting Limited | Professional & scientific | 2003 |
| N.P. Electrical Limited | Manufacturing | 1999 |
| N.Wojewoda Ltd | Professional & scientific | 2025 |
| N21 Property Limited | Real estate | 2015 |
| NAB Court Management Company Limited | Households | 2005 |
| NAB Tower Investments Limited | Real estate | 2016 |
| Nabeel Shafique Ltd | Information & communication | 2023 |