| M Eldridge Consultancy Ltd | Professional & scientific | 2022 |
| M L Panels Ltd | Wholesale & retail | 2016 |
| M&L Davy Limited | Construction | 2010 |
| M&P Models.Com Limited | Administrative & support | 2005 |
| M.P.H. Limited | Other services | 1986 |
| M.R.A.Automotive Ltd | Wholesale & retail | 2018 |
| M.T. Pearce Plumbing & Heating Services Limited | Manufacturing | 2003 |
| Mads Consulting Limited | Professional & scientific | 2017 |
| Magnalute Ltd | Manufacturing | 2024 |
| Magnitech (UK) Limited | Wholesale & retail | 2014 |
| Maison Postel LLP | | 2016 |
| Maiz Cafe Limited | Hospitality | 2023 |
| Mammoth Creative Ltd | Professional & scientific | 2020 |
| Manningtree and District Foodbank | Health & social care | 2014 |
| Manningtree Arts Ltd | Wholesale & retail | 2022 |
| Manningtree EYE & Hearing Centre Limited | Wholesale & retail | 2024 |
| Manningtree House Limited | Hospitality | 2024 |
| Manningtree Pizza Ltd | Hospitality | 2024 |
| Manningtree Practice Limited | Health & social care | 2010 |
| Manningtree Tyre & Service Centre Limited | Wholesale & retail | 2004 |
| Marc Robson Limited | Real estate | 2020 |
| Margaret's Place Management Company Limited | Real estate | 2017 |
| Marvel Associates Limited | Professional & scientific | 2016 |
| Master Saddle Fitters International Limited | Arts & recreation | 2016 |
| Mayflower Lighting Limited | Manufacturing | 2017 |
| Mbrl UK Limited | Construction | 2020 |
| Mccartney Arts Ltd | Arts & recreation | 2018 |
| MD Finance Limited | Professional & scientific | 2013 |
| Medusahair Ltd | Other services | 2007 |
| Melons Limited | Construction | 2014 |
| Mezzanine Floor Engineering Limited | Construction | 2009 |
| Middlebrook Accountancy Limited | Professional & scientific | 2025 |
| Milliphia Ltd | Wholesale & retail | 2026 |
| Minoro Consulting Limited | Professional & scientific | 2023 |
| Mirror MAN (Marylebone) Limited | Wholesale & retail | 2007 |
| Mistley Fisheries Ltd | Hospitality | 2024 |
| Mistley Kids Club Limited | Administrative & support | 2010 |
| Mistley Marine & Leisure Ltd. | Manufacturing | 1994 |
| Mitchell Training Services Ltd | Other services | 2024 |
| MJS Engineering & Fabrication Ltd | Manufacturing | 2021 |
| Moby'Z INK Ltd | Arts & recreation | 2011 |
| Model Rail Works Ltd | Manufacturing | 2025 |
| Moontree Yoga & Wellbeing Ltd | Education | 2019 |
| Morgan Levison Design Ltd | Professional & scientific | 2025 |
| Mosaic Web Design Studios Ltd | Information & communication | 2021 |
| Motorhome and Caravan Services Ltd | Wholesale & retail | 2023 |
| MPH Holdings 2020 Limited | Other services | 2020 |
| Mulligan Bros Ltd | Wholesale & retail | 2025 |
| Murray Developments Limited | Real estate | 1988 |
| Myland Management Ltd | Real estate | 2010 |
| Nathan Ashton Architectural Services Ltd | Professional & scientific | 2019 |
| Nature Optics Ltd | Wholesale & retail | 2025 |
| Navarn Limited | Administrative & support | 1997 |
| Navistitch Ltd | Wholesale & retail | 2018 |
| NCH & Partners Ltd | Professional & scientific | 2021 |
| Neptune Digital Ltd | Information & communication | 2022 |
| Nexus Infotech Ltd | Information & communication | 2024 |
| NJC Energy Consultancy Ltd | Professional & scientific | 2024 |
| Nowlan Plumbing & Heating Solutions Ltd | Construction | 2021 |
| Oak House RTM Company Limited | Extraterritorial | 2011 |
| Oakfield Wood Construction Limited | Construction | 2025 |
| Oakfield Wood Wrabness Ltd | Construction | 2024 |
| Oaktree Garage (Lawford) Limited | Wholesale & retail | 2014 |
| OMP Building Services Limited | Construction | 2022 |
| ON a Plate Growth Limited | Administrative & support | 2025 |
| One Stop Chandlery Limited | Wholesale & retail | 1998 |
| Onpoint Projects and Consulting Ltd | Construction | 2026 |
| Open Access Expeditions Ltd | Education | 2019 |
| Optimum Print Limited | Information & communication | 2014 |
| Orchard @ the Nook Limited | Manufacturing | 2021 |
| Organise My Car Ltd | Wholesale & retail | 2016 |
| Orman Landscapes Ltd | Administrative & support | 2023 |
| Orter Marketing Limited | Administrative & support | 2025 |
| OWL Marketing Solutions Limited | Professional & scientific | 2010 |
| Page Professional Resource Ltd | Professional & scientific | 2015 |
| Paradon Developments Ltd | Construction | 2020 |
| Pauls Caravan Parts Ltd | Wholesale & retail | 2017 |
| Paws and Provisions Ltd | Wholesale & retail | 2025 |
| PAY Blessed Contracts Ltd | Professional & scientific | 2014 |
| PCB Recycling Ltd | Wholesale & retail | 2017 |
| Pebble CAB Limited | Transport & logistics | 2026 |
| Penn Design Architects Limited | Professional & scientific | 2014 |
| Pentagon (Manningtree) Limited | Manufacturing | 2011 |
| Pentatope Consulting Limited | Professional & scientific | 2024 |
| Perfect Payrolls Limited | Professional & scientific | 2008 |
| Phat White Ltd | Manufacturing | 2026 |
| Physio@Home Limited | Health & social care | 2013 |
| Pickering Plumbing Services Limited | Construction | 2012 |
| Pickford Portfolio Ltd | Real estate | 2025 |
| Picts Industrial Limited | Construction | 2000 |
| Pippin Property Solutions Ltd | Real estate | 2017 |
| Plastic Collective Consulting Limited | Professional & scientific | 2026 |
| Plastic Objects Limited | Information & communication | 2013 |
| Play Consultancy & Management Ltd | Professional & scientific | 2025 |
| Play Mats Direct Limited | Wholesale & retail | 2020 |
| Plumb Bitz Limited | Extraterritorial | 2009 |
| Pontoon Hire Ltd | Administrative & support | 2008 |
| POP POP Stitches Ltd | Manufacturing | 2025 |
| PP Management Limited | Hospitality | 2024 |
| Praetory Ltd | Wholesale & retail | 2025 |