| MJD Agri Services Ltd | Construction | 2024 |
| MJF Joinery Ltd. | Construction | 2014 |
| Mjhl Property Investments Limited | Real estate | 2017 |
| MJL Plumbing & Heating (Suffolk) Limited | Construction | 2010 |
| MKB Automotive Ltd | Wholesale & retail | 2026 |
| MNJ Ltd | Wholesale & retail | 2026 |
| Moat View (Ringshall) Management Company Limited | Households | 2006 |
| Mojo Administration Solutions Limited | Administrative & support | 2010 |
| Monetr Limited | Information & communication | 2022 |
| Mongrelcroc Clothing Limited | Wholesale & retail | 2011 |
| Monocle EYE Care Ltd | Wholesale & retail | 2019 |
| Montys Imagination Ltd | Wholesale & retail | 2025 |
| Moog Properties Ltd | Real estate | 2020 |
| Moongrace Ltd | Hospitality | 2016 |
| Moor-Art Gallery Ltd | Wholesale & retail | 2020 |
| Moore Reinforced Concrete Limited | Construction | 2012 |
| Morton & Trent Limited | Real estate | 1950 |
| Moss HR Limited | Administrative & support | 2019 |
| Mototechniks Limited | Wholesale & retail | 2005 |
| Mottram Business Solutions Limited | Construction | 2015 |
| MP Plumbing & Heating Suffolk Limited | Construction | 2020 |
| MPD Tanks Ltd | Construction | 2015 |
| Mpirriecal Safety & Training Ltd | Professional & scientific | 2007 |
| MPS Solutions Limited | Information & communication | 2025 |
| MR Handy Bags Ltd | Water & waste | 2023 |
| MR RAE Limited | Construction | 2024 |
| MRB Projects Limited | Professional & scientific | 2017 |
| MRC Plant Limited | Administrative & support | 2025 |
| MRD Plumbing (Essex) Limited | Construction | 2023 |
| MRN Race Technologies Ltd | Manufacturing | 2020 |
| MTM Medica Limited | Information & communication | 2016 |
| MTP Garden Maintenance Limited | Administrative & support | 2023 |
| MTP Landscapes Limited | Administrative & support | 2023 |
| MTP Property Services Limited | Administrative & support | 2025 |
| MTY DRY Lining Ltd | Construction | 2021 |
| Muktar Ltd | Hospitality | 2020 |
| Mulbar Holdings Limited | Construction | 2024 |
| Multi-Project.Co.Uk Limited | Information & communication | 2002 |
| Muntons Pension Trustees Limited | Professional & scientific | 2009 |
| Mxchange Ltd | Wholesale & retail | 2025 |
| My Call 2 Care Limited | Administrative & support | 2019 |
| My Care at Home Limited | Health & social care | 2013 |
| My Coach Team Ltd | Professional & scientific | 2024 |
| My Gathering Limited | Hospitality | 2020 |
| My Twirl Ltd | Wholesale & retail | 2016 |
| Myanchor Ltd | Health & social care | 2026 |
| Myriad Lifestyle Ltd | Administrative & support | 2021 |
| N1 Writer Limited | Information & communication | 2014 |
| Nabab Tandoori Ltd | Hospitality | 2023 |
| Naked House Limited | Construction | 2015 |
| Nama Traders Ltd | Wholesale & retail | 2022 |
| Nano Property Limited | Real estate | 2019 |
| Narvik AI Limited | Information & communication | 2024 |
| NC Property Solutions Ltd | Construction | 2024 |
| Needham Logistics Training Ltd | Administrative & support | 2010 |
| Netherton Kwiatkowski Limited | Health & social care | 2013 |
| Network Power Installations Limited | Energy | 2008 |
| New Life Church (Suffolk) | Health & social care | 1998 |
| Newbury Pigs Limited | Agriculture & fishing | 2013 |
| Newlyn Ware Accountants Limited | Professional & scientific | 2010 |
| Newton Rose Holdings Limited | Extraterritorial | 2023 |
| Newts Property Ltd | Real estate | 2025 |
| Nexgen Engineering Solutions Limited | Construction | 2023 |
| Next Generation Flat Roofing Limited | Construction | 2014 |
| Next Spaces Property Limited | Real estate | 2022 |
| NGC Hybrid & EV Limited | Wholesale & retail | 2023 |
| Ngen Group Limited | Professional & scientific | 2018 |
| Ngpc Limited | Real estate | 2019 |
| Nick Todd Plumbing & Heating Ltd. | Construction | 2018 |
| Nigel Hefferman Designs Limited | Professional & scientific | 2011 |
| Nightwood Ltd | Financial services | 2016 |
| Nightwood Property Ltd | Construction | 2020 |
| Nightwood Real Estate Limited | Real estate | 2021 |
| NJR Tubular Solutions Limited | Manufacturing | 2009 |
| Noanknital Ltd | Professional & scientific | 2025 |
| Noble Property and Lettings Limited | Real estate | 2025 |
| Node 3 Design Limited | Professional & scientific | 2009 |
| Nolleen Properties Ltd | Real estate | 2022 |
| Nonsuch Shrubs Limited | Manufacturing | 2017 |
| Nordgen Ltd | Manufacturing | 2026 |
| Norfolk Signature Homes Ltd | Construction | 2023 |
| Norfolk Work Solutions Ltd | Construction | 2025 |
| Norson Construction Holdings Limited | Financial services | 2016 |
| North Barn Developments Limited | Real estate | 2023 |
| North Eleven Media Limited | Information & communication | 2017 |
| Northern View Properties Limited | Real estate | 2018 |
| Northgate Building Design Limited | Construction | 2019 |
| Northgate Mortgage Services Limited | Financial services | 2016 |
| Northgate Podiatry Limited | Health & social care | 2025 |
| NPR Solutions Ltd | Transport & logistics | 2021 |
| NR Live Events Limited | Arts & recreation | 2023 |
| NRG Fitness Limited | Arts & recreation | 2012 |
| Nsew Developments Ltd | Construction | 2020 |
| Nu-Digs Developments Limited | Construction | 2016 |
| NU2U Cars Limited | Wholesale & retail | 2020 |
| Nunnen Wood Property Limited | Real estate | 2024 |
| Nutshell Nursing Care Limited | Administrative & support | 2026 |
| Oakbury Management Company Limited | Real estate | 2023 |
| Oakes & Wade Limited | Professional & scientific | 2016 |
| Oakridge Environmental Services Limited | Professional & scientific | 2010 |