| Mylily Designs UK Ltd | Wholesale & retail | 2021 |
| Myriad Consultants Limited | Professional & scientific | 2016 |
| Myrtle Property's Ltd | Real estate | 2024 |
| N H Pain Ltd | Agriculture & fishing | 2023 |
| Nalla Design Ltd | Information & communication | 2010 |
| Natural Touch Holistic Therapies Ltd | Other services | 2023 |
| Navac Ltd | Wholesale & retail | 2018 |
| Nazeing Ltd | Other services | 2017 |
| Nebari Ltd | Information & communication | 2018 |
| Neliv Ltd | Professional & scientific | 2026 |
| Netman Ltd | Information & communication | 2023 |
| New Bevan Homes Limited | Construction | 2019 |
| New Bevan Prospect Limited | Real estate | 2024 |
| New Songs Administration Limited | Information & communication | 2014 |
| NGL IT Consultancy Ltd | Administrative & support | 2024 |
| NIC Ford Studios Ltd | Professional & scientific | 2024 |
| Nicholls & ROE Ltd | Financial services | 2010 |
| Nifty GAS Ltd | Construction | 2012 |
| Nimo Services Ltd | Real estate | 2022 |
| NJP Consulting Ltd | Health & social care | 2010 |
| NK & Partners Limited | Education | 2020 |
| NMR London Limited | Wholesale & retail | 2019 |
| NO 1 London Property Company Limited | Other services | 2018 |
| NO. 1 London Limited | Construction | 1998 |
| NO.4 Cambridge Drive Management Limited | Administrative & support | 1983 |
| Node Nine Limited | Information & communication | 2023 |
| Noelle Blackman Consultancy Ltd | Education | 2024 |
| Noisnep Capital Limited | Financial services | 2008 |
| Noisnep Limited | Financial services | 2009 |
| Norma Heart Limited | Information & communication | 2026 |
| Norris Grove Residents Association Limited | Households | 2000 |
| Northern Maltings (Ware) Limited | Real estate | 2013 |
| NRR Medical Services Ltd | Health & social care | 2013 |
| Nurture & Harmony Ltd | Information & communication | 2022 |
| Nvonal Limited | Hospitality | 2025 |
| NXC Collective Ltd | Wholesale & retail | 2025 |
| O.K.U Medical Limited | Health & social care | 2022 |
| Oak Building Consultancy Limited | Construction | 2020 |
| Oak Project Management Services Limited | Professional & scientific | 2023 |
| OAS Homes and Properties Limited | Households | 2025 |
| Oasis Care Group Ltd | Administrative & support | 2025 |
| OBK Limited | Professional & scientific | 2005 |
| Ocean 56 Property Investments Limited | Real estate | 2026 |
| Oculus Wealth Management (Bishop's Stortford) Limited | Financial services | 2023 |
| Oculus Wealth Management (Colchester) Limited | Financial services | 2024 |
| Offerco Limited | Extraterritorial | 2009 |
| OH Honey Bees Ltd | Agriculture & fishing | 2023 |
| Olba Business Ltd | Wholesale & retail | 2025 |
| Old Stables Management Company (2024) Ltd | Real estate | 2024 |
| Olive Tree Property Developments Limited | Construction | 2017 |
| Oliver Jack Properties Ltd | Real estate | 2021 |
| Olivia Anne Ltd | Information & communication | 2023 |
| Ollybet Limited | Hospitality | 2017 |
| Ollybet-Qsr Limited | Wholesale & retail | 2025 |
| Olseen Electrical Ltd | Wholesale & retail | 2022 |
| Omeek Afro Caribbean Food Ltd | Wholesale & retail | 2023 |
| Ompi INK Ltd | Other services | 2025 |
| ON PAR Nutrition Ltd | Manufacturing | 2020 |
| ON Point Hair Limited | Other services | 2022 |
| One Call Does IT ALL Limited | Construction | 2016 |
| OPD Group Limited | Financial services | 1996 |
| Openspdm Limited | Information & communication | 2016 |
| Operators Vault Ltd | Wholesale & retail | 2025 |
| Optimised Operations Consultant Ltd | Professional & scientific | 2023 |
| Orisami Ltd | Manufacturing | 2025 |
| ORN Holdings Ltd | Construction | 2018 |
| Otic Global Limited | Professional & scientific | 2003 |
| Outside Rooms London Limited | Administrative & support | 2022 |
| Overperform Ltd | Information & communication | 2021 |
| OWF Group Limited | Administrative & support | 2016 |
| Oxygen Property Investments Limited | Real estate | 2018 |
| P Munson Automotives Ltd | Wholesale & retail | 2020 |
| P&J Selby Property Management Ltd | Real estate | 2024 |
| Padel Ace Ltd | Arts & recreation | 2024 |
| Palm Automations Ltd | Information & communication | 2025 |
| Paradise Plants Limited | Administrative & support | 2010 |
| Paradise Wildlife Park Limited | Arts & recreation | 1981 |
| Parallel 51 Logistics Limited | Wholesale & retail | 2024 |
| Parker Security Solutions Ltd | Administrative & support | 2019 |
| Parkside Construction Services Limited | Extraterritorial | 2019 |
| Parkside Leisure Limited | Financial services | 1965 |
| Paul M Kennedy Limited | Professional & scientific | 2002 |
| PC Executives Ltd | Administrative & support | 2014 |
| PC Industries Ltd | Wholesale & retail | 2020 |
| Peace World Ltd | Wholesale & retail | 2021 |
| Pearl Organisation Ltd | Administrative & support | 2019 |
| Pentonville Management Company Limited | Households | 2008 |
| Percepta Aviation Ltd | Professional & scientific | 2020 |
| Peter Schiazza Photography Ltd | Professional & scientific | 2012 |
| Peyce Construction Ltd | Construction | 2025 |
| PG Commercial Limited | Information & communication | 2012 |
| PG Film Productions Limited | Information & communication | 2011 |
| Pharmawatch Consultancy Ltd | Professional & scientific | 2024 |
| Phoenix M Ltd | Other services | 2013 |
| Photo Date Rescue Ltd | Information & communication | 2025 |
| Phrixus Associates Ltd | Administrative & support | 2026 |
| Pink Property Maintenance Ltd | Real estate | 2025 |
| Pink Ribbon Limited | Extraterritorial | 2020 |
| Pink Ribbon Partnerships C.I.C. | Health & social care | 2025 |
| Pivot Forward Ltd | Administrative & support | 2025 |