| MSB Contracts Ltd | Construction | 2019 |
| MSC Worldwide Limited | Wholesale & retail | 2017 |
| Mscrecruitment Limited | Construction | 2024 |
| MSD Transport Ltd | Transport & logistics | 2024 |
| Msdc (Suffolk Holdings) Limited | Financial services | 2017 |
| Msfitnesss Limited | Education | 2025 |
| MSH Logistics Ltd | Transport & logistics | 2003 |
| MSM Direct Ltd | Wholesale & retail | 2024 |
| MSR Property Sourcing Limited | Real estate | 2025 |
| MST Recruitment Ltd | Administrative & support | 2021 |
| MT 53 Limited | Wholesale & retail | 2014 |
| MT Suffolk Property Services Ltd | Real estate | 2025 |
| MTB Management Services Ltd | Construction | 2016 |
| MTC Solutions Ltd | Professional & scientific | 2024 |
| Mtck Limited | Wholesale & retail | 2024 |
| Mtec Electrical Services Ltd | Construction | 2023 |
| Mtentertainments Limited | Arts & recreation | 2019 |
| MTF Generator Services Limited | Professional & scientific | 2015 |
| MTG Investments Ltd | Professional & scientific | 2021 |
| MTO Contracting Ltd | Construction | 2026 |
| MTS Ipswich Ltd | Transport & logistics | 2021 |
| MU K Flame Ltd | Hospitality | 2025 |
| Mucha Murapa Ltd | Professional & scientific | 2021 |
| Muchimba Ltd | Health & social care | 2019 |
| Muchoarte Ltd | Hospitality | 2024 |
| Mufasa Shop NET Ltd | Wholesale & retail | 2025 |
| Muffin ME Limited | Wholesale & retail | 2024 |
| Muhdo Group Ltd | Financial services | 2025 |
| Muktader Ltd | Wholesale & retail | 2026 |
| Mullquest Limited | Wholesale & retail | 1993 |
| Multifreight Holdco Limited | Information & communication | 2023 |
| Multifreight Limited | Information & communication | 1994 |
| Multimotion Forwarding Ltd | Transport & logistics | 2022 |
| Multiquotetime Ltd | Wholesale & retail | 2022 |
| Multiserve (E.A.) Limited | Construction | 2004 |
| Multisys Limited | Administrative & support | 2021 |
| Multithread Holdings Limited | Financial services | 2021 |
| Multitrance Build Ltd | Manufacturing | 2022 |
| Multitrans Group Ltd | Wholesale & retail | 2019 |
| Multoplat Ltd | Manufacturing | 2002 |
| Mung Bean Ltd | Wholesale & retail | 2024 |
| Munro Importers Limited | Wholesale & retail | 2006 |
| Munro Medical Solutions Limited | Wholesale & retail | 2020 |
| Murapa Brothers (UK) Ltd | Financial services | 2012 |
| Murray Gibson Associates Ltd | Administrative & support | 2016 |
| Murrayside Community Development C.I.C. | Other services | 2021 |
| Murrayside Spartans Academy CIC | Education | 2025 |
| Murrill Forge Limited | Education | 2023 |
| Muscade Limited | Professional & scientific | 1994 |
| Museum of the Environment - Mote Community Interest Company | Arts & recreation | 2023 |
| Museum Street Developments Ltd | Construction | 2018 |
| Music Events Services Ltd | Arts & recreation | 2025 |
| Music Prescription CIC | Arts & recreation | 2023 |
| Music World Ltd | Wholesale & retail | 2011 |
| Musicool Activities CIC | Health & social care | 2026 |
| Musketeers Tech Limited | Information & communication | 2023 |
| Musna Limited | Professional & scientific | 2025 |
| Mutual Media (UK) Limited | Administrative & support | 2007 |
| Mutual Media Limited | Administrative & support | 2008 |
| MV Amuda Limited | Administrative & support | 2026 |
| MV Assets Ltd | Real estate | 2019 |
| MVG Plants Limited | Wholesale & retail | 2023 |
| Mvjw Limited | Health & social care | 2024 |
| MVS Recovery Ltd | Transport & logistics | 2020 |
| MW Trade Marks Limited | Professional & scientific | 2009 |
| MWP Limited | Professional & scientific | 1973 |
| MWT Wealth Management Limited | Financial services | 2017 |
| My 96 Ltd | Hospitality | 2023 |
| My Big FAT Wedding Disco.Com Ltd | Administrative & support | 2014 |
| My Boatworld Ltd | Wholesale & retail | 2023 |
| My Car World Ltd | Wholesale & retail | 2026 |
| My Green Energy Group Limited | Construction | 2024 |
| My Hakka Ltd | Hospitality | 2025 |
| My Light Electrical Services Ltd | Construction | 2011 |
| My Marketing Horizon Limited | Information & communication | 2025 |
| My Mystery Limited | Information & communication | 2006 |
| My ND Place Ltd | Education | 2020 |
| My Online Accountant Ltd | Professional & scientific | 2023 |
| My Phone Universe Ltd | Wholesale & retail | 2021 |
| My Tech VA Limited | Administrative & support | 2022 |
| My the 24 Ltd | Transport & logistics | 2019 |
| Myaj Property Limited | Real estate | 2017 |
| Mybest Local Ltd | Wholesale & retail | 2021 |
| Mydriver Ltd | Transport & logistics | 2015 |
| Myers Orthopaedics Limited | Health & social care | 2024 |
| Myfika Limited | Education | 2024 |
| Mygiftstore Ltd | Wholesale & retail | 2025 |
| Mykotype Designs Ltd | Manufacturing | 2025 |
| Mylo's Pizza Ltd | Hospitality | 2024 |
| Mymz Furniture Gallery Ltd | Wholesale & retail | 2026 |
| Myrese Limited | Health & social care | 2022 |
| Myriad Properties Ltd | Real estate | 2017 |
| Myrtle Property Partnership Ltd | Real estate | 2025 |
| Mysmartobject Limited | Administrative & support | 2020 |
| Mysteries With a Heart Ltd | Information & communication | 2025 |
| Mystery Inc Ltd | Arts & recreation | 2023 |
| Mythic Forge Limited | Wholesale & retail | 2025 |
| Mythical Origins Group Limited | Information & communication | 2024 |
| MZR Transport Ltd | Transport & logistics | 2025 |
| Mélangelarou Ltd | Wholesale & retail | 2024 |