| Mood Board Interiors Limited | Professional & scientific | 2013 |
| Moody Building Limited | Real estate | 2006 |
| Moody Investments Limited | Real estate | 1980 |
| Moody Venture Capital LLP | | 2014 |
| Moonstone Studio Ltd | Arts & recreation | 2025 |
| Morgan Reeves Limited | Real estate | 2023 |
| Moriarty Oak Limited | Construction | 2026 |
| Mortleys Dispense Ltd | Other services | 2018 |
| Mosscope Limited | Real estate | 1992 |
| Mount Street Developments Limited | Construction | 2012 |
| MSD Ashwells Ltd | Real estate | 2024 |
| MSD Downham Limited | Real estate | 2025 |
| MSD Epping Limited | Real estate | 2022 |
| MSD Lamberts Farm Limited | Real estate | 2024 |
| MSD Ramsden Heath Management Company Limited | Real estate | 2024 |
| MSS Childcare Ltd | Health & social care | 2023 |
| Murray Wood Limited | Professional & scientific | 2015 |
| Mustang Wedding Cars Essex Limited | Administrative & support | 2024 |
| MVC Development Finance Ltd | Financial services | 2024 |
| MW Home Services Ltd | Construction | 2024 |
| Mwcrook Transport Limited | Transport & logistics | 2018 |
| My Counselling & Psychology Services LLP | | 2012 |
| My Talent Platform Limited | Information & communication | 2018 |
| Myanmar Community U.K. Limited | Public administration | 2021 |
| N & L Property Ltd | Real estate | 2018 |
| N G Moloney Accountants Limited | Professional & scientific | 2008 |
| N&Z Building Ltd | Administrative & support | 2015 |
| NAILS66 Ltd | Other services | 2022 |
| NAILS@66 Ingatestone Ltd | Other services | 2022 |
| National Insulation Supplies Ltd | Wholesale & retail | 2022 |
| Natural Foundations | Arts & recreation | 2013 |
| Nava + ME Ltd | Wholesale & retail | 2023 |
| Navarre Interiors Limited | Construction | 1978 |
| NC Wealth Management Services Limited | Professional & scientific | 2018 |
| NCU Construction & Renovation Limited | Construction | 2024 |
| NCU Properties Limited | Construction | 2025 |
| Nelson ST Properties Ltd | Real estate | 2015 |
| NET Zero Foods Limited | Hospitality | 2023 |
| Network Training Partnership Ltd | Education | 2017 |
| Nevest Limited | Hospitality | 2015 |
| New Hall Properties (Eastern) Ltd | Real estate | 2011 |
| New Hall Properties (Southern) Limited | Real estate | 2004 |
| New Leaf Landscapes & Designs Ltd | Administrative & support | 2023 |
| New Road Gosfield Residents Limited | Households | 2023 |
| New Water Labs Ltd | Professional & scientific | 2025 |
| Newman Empire Limited | Construction | 2005 |
| Next Door Estates Ltd | Real estate | 2022 |
| Next Generation Sustainable Technology and BIO Labs Ltd | Professional & scientific | 2026 |
| Nine Ashes Accounting Limited | Professional & scientific | 2016 |
| Noise PR Limited | Professional & scientific | 2013 |
| Northbeck Investments Ltd | Financial services | 2022 |
| Norton Heath Development Limited | Extraterritorial | 2015 |
| Nott Office Limited | Wholesale & retail | 2010 |
| Novameat Tech (UK) Ltd | Manufacturing | 2023 |
| Noventus Partners Limited | Administrative & support | 2001 |
| Novus Risk Solutions Limited | Financial services | 2009 |
| Ns&A Ltd | Professional & scientific | 2025 |
| NU Squared Limited | Real estate | 2006 |
| NU Twyford Limited | Real estate | 2023 |
| Nunn Construction Ltd | Construction | 2023 |
| Nunn Property Group Ltd | Construction | 2022 |
| Nuovant Ltd | Wholesale & retail | 2023 |
| Nusic Sounds LLP | | 2011 |
| O4Y Agency L.P. | | 2024 |
| OCQ Construction Ltd | Construction | 2025 |
| OCR Sprint Limited | Arts & recreation | 2026 |
| Octo Recruitment Limited | Administrative & support | 2024 |
| Office Furniture & Supplies Limited | Wholesale & retail | 2009 |
| OH HI Tomorrow Ltd | Professional & scientific | 2024 |
| OH ME OH My Ltd | Professional & scientific | 2023 |
| Oikos Partnership Limited | Real estate | 2023 |
| Old Granary Stables Limited | Agriculture & fishing | 2023 |
| Oliver William Jones Limited | Administrative & support | 2010 |
| OMA Electrical Limited | Construction | 2014 |
| Omen Limited | Arts & recreation | 2024 |
| ON Broadcast Ltd | Professional & scientific | 2024 |
| Oncoexcellence Limited | Health & social care | 2014 |
| Osprey House (Management) Limited | Real estate | 2002 |
| Ourcity Construction Ltd | Real estate | 2016 |
| Ourcity Developments Ltd | Real estate | 2018 |
| Ourcity Estate Ltd | Real estate | 2023 |
| Ourcity Letting Ltd | Real estate | 2024 |
| Oxovi Limited | Information & communication | 2025 |
| Ozer Property Limited | Real estate | 2021 |
| P & P Building Solutions Ltd | Construction | 2015 |
| P J Coffey Limited | Professional & scientific | 2009 |
| P Van DEN Brande Ltd | Financial services | 2024 |
| P&W Group Holdings Limited | Financial services | 2022 |
| Palmers Barbers Ltd | Other services | 2022 |
| Palmtree Associates Limited | Real estate | 2004 |
| Paramount Flooring Ltd | Construction | 2022 |
| Parish Ventures Limited | Real estate | 2017 |
| Parking Personnel Ltd | Administrative & support | 2019 |
| Parklanes Wykeham Childcare Limited | Education | 2006 |
| Patam Group Ltd | Professional & scientific | 2018 |
| Patrick Green Limited | Wholesale & retail | 2000 |
| PCP Real Estates Limited | Real estate | 2017 |
| PD Donnelly Properties Ltd | Real estate | 2025 |
| Peachey Media Consultancy Limited | Information & communication | 2017 |
| Peanuts Properties Limited | Real estate | 2015 |