| Mobius Group Limited | Professional & scientific | 2020 |
| Modus Operandi Films Limited | Information & communication | 1993 |
| Molz Gynae Limited | Health & social care | 2023 |
| Monks Oak Limited | Real estate | 2022 |
| More Time to DO Less Ltd | Information & communication | 2025 |
| More-Build Ltd | Construction | 2019 |
| Morgan's Farm Limited | Hospitality | 2014 |
| Mortgage Advice Gallery Ltd | Financial services | 2022 |
| Mortgage Link Limited | Financial services | 2006 |
| Mossford Properties Limited | Real estate | 2017 |
| Moxa Hospitality & Leisure Limited | Professional & scientific | 2010 |
| MP Chartered Architects Ltd | Professional & scientific | 2022 |
| MR. M Male Grooming Limited | Other services | 2013 |
| Mrcs Bathrooms & Kitchens Ltd | Construction | 2024 |
| Mreinvest Ltd | Financial services | 2024 |
| MS Fire Protection Ltd | Construction | 2020 |
| Msurveying Ltd | Professional & scientific | 2026 |
| MTS Property Limited | Real estate | 2017 |
| Mulberry Retreat and Leisure Limited | Hospitality | 1997 |
| Munjeet.Com Limited | Information & communication | 2007 |
| Murphyz Ltd | Professional & scientific | 2011 |
| My Lane Investments Limited | Real estate | 2019 |
| N & B Export Trading Limited | Wholesale & retail | 2010 |
| N&C Catering Ltd | Hospitality | 2016 |
| Nails 21 Ltd | Other services | 2021 |
| Nalvic Travel Limited | Administrative & support | 2016 |
| Nancy Chandler Limited | Other services | 2018 |
| Nashira Topco Limited | Financial services | 2023 |
| Naturalawns Limited | Wholesale & retail | 2016 |
| Nearly There Holdings Ltd | Manufacturing | 2018 |
| Neon Electrical Services Limited | Construction | 2017 |
| Netteswell Limited | Other services | 2018 |
| Network Tours Limited | Administrative & support | 1997 |
| Network Training & Recruitment Group Ltd | Education | 2026 |
| Never Forget Yvette Ltd | Professional & scientific | 2012 |
| Newson Construction Limited | Construction | 2017 |
| Nicks Wheels Ltd | Wholesale & retail | 2025 |
| Night Storm Holdings Limited | Financial services | 2025 |
| NMJ Property Limited | Real estate | 2022 |
| NO Rarity Limited | Wholesale & retail | 2023 |
| Nomad Electrical Services Ltd | Construction | 2017 |
| Nori Sushi Limited | Wholesale & retail | 2013 |
| Normans Way Management Limited | Real estate | 2004 |
| Norris Properties Limited | Construction | 2015 |
| Northbridge Trade Limited | Wholesale & retail | 2025 |
| Nourezay Limited | Wholesale & retail | 2026 |
| NSS Trading Limited | Hospitality | 2020 |
| Nucentz Clothing Limited | Wholesale & retail | 2016 |
| Nucifera Limited | Professional & scientific | 2021 |
| O C Combustion Limited | Professional & scientific | 2015 |
| O Donovan Properties Ltd | Construction | 2020 |
| Oakbridge Facility Maintenance Ltd | Construction | 2022 |
| Oakland Home Improvements Limited | Construction | 2012 |
| Oaklands (Chipping Ongar) Management Limited | Households | 1999 |
| Oaktree IT Solutions Ltd | Information & communication | 2019 |
| Observe Solutions Limited | Water & waste | 2004 |
| Oliver Rolfe Property Services Limited | Real estate | 2023 |
| One & Only Events Ltd | Hospitality | 2025 |
| Ongar Bridge Holdings Limited | Wholesale & retail | 2002 |
| Ongar Bridge Motor Company Limited | Wholesale & retail | 1996 |
| Ongar Business Solutions Limited | Professional & scientific | 2016 |
| Ongar Catering Ltd | Hospitality | 2018 |
| Ongar Community Sports Limited | Arts & recreation | 2016 |
| Ongar Cuts Ltd | Other services | 2025 |
| Ongar DRY Cleaning Ltd | Other services | 2025 |
| Ongar Food & Wine Ltd | Wholesale & retail | 2025 |
| Ongar Furniture Limited | Wholesale & retail | 2016 |
| Ongar Gents Barber Ltd | Other services | 2021 |
| Ongar Lawn Tennis Club Limited | Arts & recreation | 2016 |
| Ongar Pre-School, Breakfast & After School Club Ltd | Health & social care | 2023 |
| Ongar Prestige and 4 X 4 Ltd | Wholesale & retail | 2020 |
| Ongar Supermarkets Ltd | Wholesale & retail | 2018 |
| Ongar Thai Ltd | Hospitality | 2019 |
| Only Pure Ltd | Wholesale & retail | 2022 |
| Onlyway Green Ltd | Information & communication | 2024 |
| Opcure Limited | Health & social care | 2005 |
| Openshare Management Limited | Information & communication | 2003 |
| Optimal Fitness Training Limited | Other services | 2018 |
| Optimasensus Limited | Information & communication | 2024 |
| Orbit Care Solutions Limited | Health & social care | 2023 |
| Orchards Property Limited | Real estate | 2025 |
| Oseactive Ltd | Wholesale & retail | 2025 |
| Oulder Limited | Wholesale & retail | 2025 |
| OVAL3 Limited | Professional & scientific | 2025 |
| Oxford Food Supplies Ltd | Wholesale & retail | 2023 |
| P & L Business Development Limited | Administrative & support | 2014 |
| P & L French Ltd | Construction | 2014 |
| P&S Plumbing Limited | Other services | 2019 |
| P.B. Frost Limited | Agriculture & fishing | 1943 |
| P.H. Byproducts Ltd | Water & waste | 2020 |
| PAB Services Ltd | Administrative & support | 2024 |
| Padel Unites People Ltd | Administrative & support | 2025 |
| Page Paper Sales Limited | Wholesale & retail | 2014 |
| Pagepart Limited | Real estate | 1995 |
| Paladin Outsourcing Ltd | Professional & scientific | 2022 |
| Palladian Leisure Limited | Professional & scientific | 2010 |
| Palladian NXD Limited | Professional & scientific | 2017 |
| Paragon Contractors Ltd | Construction | 2026 |
| Paul Harries Limited | Professional & scientific | 2002 |
| Paul Parker Electrical Limited | Construction | 2010 |