| Mysalonmanager Ltd | Other services | 2019 |
| Nadimi Properties Ltd | Real estate | 2021 |
| Nadmyr Invest Limited | Health & social care | 2010 |
| Naguvana Ltd | Real estate | 2022 |
| Nail Design Dunmow Limited | Other services | 2019 |
| Nalano Services Ltd | Transport & logistics | 2015 |
| Nanny Poppins Ltd | Administrative & support | 2023 |
| Nannying With Laura Limited | Health & social care | 2025 |
| Neurobridge Technologies Limited | Information & communication | 2026 |
| New Blue Horizon Limited | Professional & scientific | 2013 |
| New Frontier Systems Limited | Professional & scientific | 2025 |
| New Happy Garden Dunmow Limited | Hospitality | 2019 |
| Newfields Agricultural Holdings Limited | Agriculture & fishing | 2016 |
| Newhall Retail Limited | Wholesale & retail | 2018 |
| Newman Personnel Ltd | Administrative & support | 2009 |
| Newmond Properties Limited | Professional & scientific | 2016 |
| Nexalink Digital Ltd | Information & communication | 2023 |
| Nexgen Air Systems Ltd | Construction | 2022 |
| Next Key London Limited | Real estate | 2025 |
| NHO Consultancy Ltd | Wholesale & retail | 2019 |
| Nickolds Homes Ltd | Real estate | 2025 |
| Nicoara Covaci Ltd. | Transport & logistics | 2015 |
| Nicol Taylor Consulting Limited | Professional & scientific | 2010 |
| Nigel Smith Concept Consultancy Limited | Professional & scientific | 2018 |
| Nikola Driving Services Ltd | Transport & logistics | 2016 |
| Nisa Constructions Limited | Construction | 2015 |
| NM White Developments Ltd | Construction | 2023 |
| Nobber Village Limited | Hospitality | 2014 |
| Nodax UK Ltd | Wholesale & retail | 2011 |
| Nomis Consultancy Limited | Professional & scientific | 2011 |
| None for the Road Limited | Hospitality | 2025 |
| NOO YU CIC | Arts & recreation | 2016 |
| Norasport Supermoto Ltd | Arts & recreation | 2015 |
| North Essex Recycling Ltd | Water & waste | 2018 |
| North Essex Waste Recycling Ltd | Water & waste | 2026 |
| Novo Dental Limited | Health & social care | 2023 |
| Novus Nine Ltd | Information & communication | 2025 |
| NPB Associates Limited | Professional & scientific | 2013 |
| NRG Electrical Ltd | Construction | 2012 |
| Nurtured Foods Limited | Wholesale & retail | 2015 |
| NUT Safety Limited | Professional & scientific | 2013 |
| O 3 E Limited | Professional & scientific | 2011 |
| Oak & Rose Joinery Ltd | Construction | 2023 |
| Oak View Tree & Landscapes Services Ltd | Administrative & support | 2024 |
| Oaklands Investments (ST. Albans) Limited | Financial services | 1959 |
| Oakmont Logistics Ltd | Transport & logistics | 2026 |
| Oatech Ltd | Construction | 2020 |
| Occupational Therapy Plus Limited | Health & social care | 2009 |
| Ocean Industrial Flooring Services Limited | Wholesale & retail | 2004 |
| Octain Limited | Transport & logistics | 2000 |
| Octain Logistics Limited | Transport & logistics | 2020 |
| OG Conversions Limited | Construction | 2021 |
| OG Driver Programme Ltd | Education | 2026 |
| Ohsh Ltd | Education | 2025 |
| OJJ Essex Ltd | Administrative & support | 2025 |
| Oldworld Creative Limited | Information & communication | 2011 |
| Olin Limited | Construction | 2020 |
| Oliveswood Accountancy Ltd | Professional & scientific | 2018 |
| Omalleys Vehicle Recovery Limited | Wholesale & retail | 2017 |
| Omniscient Construction Ltd | Construction | 2021 |
| Omore Aesthetics Ltd | Other services | 2026 |
| ON and on Trading Limited | Manufacturing | 2019 |
| One Investment Group Limited | Real estate | 2002 |
| Ongar Road Number One Limited | Real estate | 2025 |
| Online Trade Sales Ltd | Wholesale & retail | 2020 |
| Ontrak Financial Planning Limited | Financial services | 2013 |
| OPC Building Services Ltd | Construction | 2018 |
| OPC Surveys Ltd | Extraterritorial | 2023 |
| Operon Flow Limited | Information & communication | 2015 |
| Operon Health Limited | Information & communication | 2016 |
| Optimal Wellness Limited | Health & social care | 2024 |
| Optimum Visual Solutions Ltd | Wholesale & retail | 2025 |
| Orca Global Solutions Ltd | Wholesale & retail | 2020 |
| Orchid Automotive Limited | Professional & scientific | 2018 |
| Orchid Construction Services Limited | Professional & scientific | 2023 |
| Origin Health and Lifestyle Ltd | Professional & scientific | 2025 |
| Orion Signs Ltd | Manufacturing | 2016 |
| OUR Garden Hens Ltd | Manufacturing | 2015 |
| OUR Vision, Your Future Ltd | Arts & recreation | 2020 |
| Outland Equestrian Limited | Agriculture & fishing | 2024 |
| Outland Group Limited | Wholesale & retail | 2020 |
| Overbrook Automotive Limited | Wholesale & retail | 2026 |
| Overbrook Solutions Limited | Construction | 2014 |
| Overload Events Limited | Arts & recreation | 2011 |
| Overseas Moving Limited | Other services | 1986 |
| OVT Pedicab Ltd | Transport & logistics | 2019 |
| OZA Concepts & Solutions Limited | Professional & scientific | 2014 |
| P & a Wood (UK) Limited | Wholesale & retail | 2009 |
| P & a Wood LLP | | 2003 |
| P & L Commissioning Services Limited | Information & communication | 2022 |
| P a Brock Ltd | Administrative & support | 2013 |
| P D Wheatland Limited | Administrative & support | 2003 |
| P W Builders Essex Limited | Construction | 2023 |
| P. Howard Heating Installations Limited | Real estate | 1964 |
| P. Howard Industrial Pipework Services Limited | Real estate | 1973 |
| P.J. Margle Heating Limited | Construction | 2002 |
| Pages Accountancy Solutions Limited | Professional & scientific | 2023 |
| Paintwerx Ltd | Wholesale & retail | 2021 |
| Palli Ltd | Health & social care | 2015 |
| Panache Constructions Ltd | Construction | 2018 |