| Mighty Home Group Ltd | Wholesale & retail | 2025 |
| Migliori Ltd | Administrative & support | 2023 |
| Migrate Group Limited | Administrative & support | 2021 |
| Mihady Limited | Transport & logistics | 2024 |
| Mihaella Ltd | Health & social care | 2018 |
| Mihaidaniel Transport Limited | Administrative & support | 2016 |
| Miig Haulage Limited | Transport & logistics | 2025 |
| Miko United Group Limited | Transport & logistics | 2025 |
| Mikrobi Transport Ltd | Transport & logistics | 2019 |
| Miksa Limited | Transport & logistics | 2016 |
| Mila & Sybil Limited | Real estate | 2024 |
| Mila Homes Limited | Real estate | 2017 |
| Milcho Ltd | Transport & logistics | 2023 |
| Mildmay Road (Chelmsford) Management Limited | Households | 1999 |
| MILENIUM82 Limited | Transport & logistics | 2020 |
| Miles Drainage 20 Ltd | Construction | 2011 |
| Milestone Ipswich Limited | Real estate | 2007 |
| Military Performance Coach Ltd | Other services | 2021 |
| Milk & Moore Ltd | Wholesale & retail | 2024 |
| Milks Comic Limited | Information & communication | 2025 |
| Mill Acres Limited | Hospitality | 1999 |
| Mill Construction (East Anglia) Ltd | Construction | 2000 |
| Mill Farm Place Management Company Limited | Households | 2018 |
| Mill Grove (Stowmarket) Management Company Limited | Households | 2021 |
| Mill Lane Pubs Ltd | Hospitality | 2017 |
| Mill Road Drive Management Company Limited | Households | 1999 |
| Millbank Livery Limited | Agriculture & fishing | 2018 |
| Millday Limited | Hospitality | 2011 |
| Miller - Jones Limited | Real estate | 1949 |
| Millers Family Ltd | Hospitality | 2025 |
| Millers Fish & Chips Limited | Hospitality | 2017 |
| Millers Gate (Soham) Management Company Limited | Households | 2021 |
| Millers Grill Ltd | Hospitality | 2025 |
| Millers Windows and Doors Ltd | Construction | 2025 |
| Millie and Belle Designs Ltd | Wholesale & retail | 2023 |
| Millie Asset Holdings Ltd | Real estate | 2025 |
| Milligan Consultants Limited | Information & communication | 2015 |
| Milling and Turning Limited | Extraterritorial | 2014 |
| Mills Heating Limited | Construction | 2012 |
| Mills Property Ipswich Ltd | Real estate | 2023 |
| Millsopps Limited | Real estate | 2004 |
| Millstream Properties Ltd | Real estate | 2015 |
| Milly Property Solutions Limited | Real estate | 2018 |
| Milner Strategic Marketing Limited | Professional & scientific | 2006 |
| Mimi MAY Foundation Ltd | Education | 2026 |
| Mimi MAY Media Group Ltd | Information & communication | 2026 |
| Mimibear Ltd | Wholesale & retail | 2018 |
| Mimobileclub Store Ltd | Wholesale & retail | 2023 |
| MIN Transport Services Ltd | Transport & logistics | 2023 |
| Minagabeena Ltd | Wholesale & retail | 2026 |
| Minchins Catering Limited | Hospitality | 2016 |
| Mindai Limited | Information & communication | 2023 |
| Mindfidelity Ltd | Professional & scientific | 2023 |
| Mindfield International Ltd | Professional & scientific | 2020 |
| Mindful Fitness Academy Ltd | Health & social care | 2025 |
| Mindful Naturals Ltd | Other services | 2020 |
| Mindlink TEC Ltd | Information & communication | 2023 |
| Mindsync Ltd | Education | 2026 |
| Minerva Law Limited | Professional & scientific | 2012 |
| Minhas Painting & Decorating Limited | Construction | 2023 |
| Minime Mindfulness Suffolk Ltd | Other services | 2024 |
| Minimum Fitness Limited | Wholesale & retail | 2021 |
| Ministry of Pet Ltd | Manufacturing | 2023 |
| Minstrel's Motors UK Ltd | Wholesale & retail | 2025 |
| Mint Cars Ipswich Ltd | Wholesale & retail | 2023 |
| Minute Work Limited | Education | 2024 |
| Miraly Ltd | Transport & logistics | 2019 |
| Miramat Barbers and Beauty Lounge Ltd | Other services | 2026 |
| Miran Fish Ltd | Hospitality | 2025 |
| Miraya Enterprise Ltd | Real estate | 2024 |
| Mirezra Beauty Ltd | Other services | 2024 |
| Mirkomil for Trade Ltd | Real estate | 2024 |
| Mirrormaze Communications Ltd | Information & communication | 2023 |
| MIS Focul Duhului Sfant Ltd | Other services | 2025 |
| Misbahullah Ltd | Health & social care | 2024 |
| Misfuelled Car Fixer Ltd | Wholesale & retail | 2021 |
| Misha Impex Ltd | Wholesale & retail | 2022 |
| Mishiraya's Kitchen Ltd | Hospitality | 2026 |
| Misote Technologies Ltd | Information & communication | 2025 |
| Miss Pears Limited | Wholesale & retail | 2021 |
| Miss Quirky Kicks Limited | Wholesale & retail | 2018 |
| Mission Home Care Ltd | Health & social care | 2025 |
| Mission to Music CIC | Education | 2023 |
| Mistarus LP | | 2021 |
| Mistley Place Limited | Real estate | 2015 |
| Misurare Limited | Professional & scientific | 2003 |
| Mitoba Computer Systems Limited | Extraterritorial | 2017 |
| Mitoba Property Service Limited | Real estate | 2020 |
| MIX and Munch Limited | Hospitality | 2019 |
| Mixbrow Limited | Construction | 1973 |
| Mixentra Ltd | Wholesale & retail | 2025 |
| Miyabeh Express Kebab Ltd | Hospitality | 2025 |
| Mizu Ipswich Limited | Hospitality | 2015 |
| Mizu NB Limited | Hospitality | 2025 |
| Mizzen Ventures LLP | | 2025 |
| MJ Grant Group Limited | Construction | 2026 |
| Mj's Nordic Bakery Limited | Wholesale & retail | 2026 |
| MJ10 Properties Ltd | Households | 2026 |
| MJB Accounting Ltd | Professional & scientific | 2020 |
| MJB Asset Management Ltd | Real estate | 2019 |