| LOG Cabin Holidays Ltd | Hospitality | 2021 |
| Loomes Roofing Contractors Limited | Construction | 2019 |
| Louis Joes Ltd | Hospitality | 2019 |
| Louise Goulding Nutrition Ltd | Health & social care | 2023 |
| Lowery IT Business Solutions Ltd | Information & communication | 2019 |
| LU Suli UK Limited | Manufacturing | 2023 |
| M D Saunders Motor Repairs Ltd | Wholesale & retail | 2012 |
| M Fuller Building Services Limited | Construction | 2022 |
| M.Draper Construction Limited | Manufacturing | 2002 |
| M3 Property Partners Ltd | Real estate | 2012 |
| Mack Publishing Limited | Information & communication | 2012 |
| Magdalen Street Management Limited | Real estate | 1997 |
| Mallettea Ltd | Agriculture & fishing | 1997 |
| Malthouse Security Limited | Administrative & support | 2009 |
| Maltsters' Yard Residents Management Company Limited | Households | 2013 |
| Manazilna Ltd | Real estate | 2023 |
| MAP Portfolio Ltd | Construction | 2022 |
| Market Cross House Limited | Real estate | 2010 |
| Martin Edward Ltd | Financial services | 2022 |
| Matspace Studios Ltd | Arts & recreation | 2022 |
| Matt Duddleston SET Design Limited | Construction | 2013 |
| Mccallums Services Ltd | Professional & scientific | 2020 |
| Meles Meles Limited | Information & communication | 2016 |
| Mellis Welding Supplies Limited | Wholesale & retail | 1985 |
| Mellowford Services Limited | Professional & scientific | 1934 |
| Mercatus Marketing Limited | Information & communication | 2001 |
| Metavoxx Business Ltd | Information & communication | 2018 |
| MIB Flat Roofing Limited | Construction | 2022 |
| Microfi Limited | Professional & scientific | 2012 |
| MID Suffolk Poultry Limited | Agriculture & fishing | 2003 |
| MID Suffolk PUB Co Ltd | Hospitality | 2021 |
| Mikesmood Investments Limited | Financial services | 2013 |
| Mill Street Management (Gislingham) Company Limited | Households | 2018 |
| Moat Yard Limited | Agriculture & fishing | 2025 |
| Mode Engineers Limited | Professional & scientific | 2024 |
| Mondo Finance Limited | Financial services | 2015 |
| Moores Holdings Limited | Financial services | 2019 |
| Moores Refrigeration Controlled Transport Limited | Transport & logistics | 1974 |
| Moors Watering Hole Ltd | Hospitality | 2016 |
| More Moto Limited | Wholesale & retail | 2011 |
| Mpsunshine Ltd | Transport & logistics | 2019 |
| Mrct Holdings Limited | Financial services | 2019 |
| Mrct Limited | Extraterritorial | 2023 |
| MRM Finance Ltd | Financial services | 2025 |
| Mudie & Troughton Farms Limited | Agriculture & fishing | 1964 |
| Muta Limited | Other services | 1919 |
| MV & Sons Forklift Training Services Ltd | Other services | 2012 |
| Mxpro Limited | Construction | 2016 |
| Myworkhive Ltd | Professional & scientific | 2016 |
| Napier Quill Limited | Health & social care | 1987 |
| NBC Design, Manage & Construct Ltd | Construction | 2021 |
| NHH Takeaway Ltd | Hospitality | 2026 |
| Nibbana Mantra Ltd | Professional & scientific | 2024 |
| Nick Cook Design Ltd | Construction | 2015 |
| Nick Dale Naturopath Ltd | Health & social care | 2025 |
| Nikita Ltd | Health & social care | 2024 |
| Nimble Studio Limited | Information & communication | 2011 |
| Noblebarns Ltd | Construction | 2024 |
| Norfolk & Suffolk Farms Ltd | Agriculture & fishing | 1975 |
| Norfolk and Suffolk Pigs Limited | Agriculture & fishing | 1976 |
| Oaksmere Investments Limited | Real estate | 2018 |
| Oaksmere Limited | Hospitality | 2014 |
| OCF Imports Limited | Wholesale & retail | 2019 |
| Old Dairy Court Management Limited | Households | 2012 |
| One for FUN International Limited | Financial services | 2015 |
| Optimal Heating Suffolk Ltd | Construction | 2026 |
| Original Homewares Limited | Wholesale & retail | 2021 |
| Oryx Brickwork Limited | Construction | 2022 |
| Overridge Ltd | Wholesale & retail | 2025 |
| OYO Land Management (Belvedere) Limited | Real estate | 2009 |
| OYO Land Management (Castle Vale) Limited | Real estate | 2008 |
| OYO Land Management (Littlehampton) Limited | Real estate | 2008 |
| OYO Land Management (Sittingbourne) Limited | Real estate | 2009 |
| Ozbozz Limited | Administrative & support | 2015 |
| P J Fenning Limited | Agriculture & fishing | 2025 |
| Palfrey & Co Limited | Wholesale & retail | 2024 |
| Peac Services Ltd | Other services | 2026 |
| Pentacle Consulting UK Limited | Information & communication | 2019 |
| Permastore Agricultural Products Limited | Professional & scientific | 1984 |
| Permastore Group Limited | Professional & scientific | 2001 |
| Permastore Holdings Limited | Professional & scientific | 1990 |
| Permastore Limited | Manufacturing | 1931 |
| Pioneer Caravans Limited | Professional & scientific | 1960 |
| Place Farm Barns Ltd | Professional & scientific | 2000 |
| Plena Social Value Solutions Limited | Professional & scientific | 2019 |
| Plinth Medical Limited | Manufacturing | 2016 |
| PMA Solutions Limited | Wholesale & retail | 2022 |
| Premier Labelling Solutions Limited | Manufacturing | 2004 |
| Prestige Pool Floors Ltd | Extraterritorial | 2008 |
| Pro Driver Hire Ltd | Transport & logistics | 2015 |
| Progress Commercial Property Ltd | Real estate | 2025 |
| Progress EYE Ltd | Professional & scientific | 2026 |
| Promedia Equipment Ltd | Administrative & support | 2025 |
| Promising Properties Ltd | Real estate | 2023 |
| Property Care (East Anglia) Limited | Administrative & support | 2003 |
| Proponics Ltd | Professional & scientific | 2021 |
| Pumpkin Barn Ltd | Wholesale & retail | 2023 |
| Purple 1982 Ltd | Real estate | 2020 |
| Py@Work Limited | Hospitality | 2006 |
| Quantellia DI (UK) Ltd | Extraterritorial | 2025 |