| Novobelle Counselling Ltd | Health & social care | 2026 |
| NPM Electrical Ltd | Construction | 2019 |
| NQJ Services Ltd | Construction | 2025 |
| Nrtt Ltd | Construction | 2023 |
| NTR Planning Limited | Professional & scientific | 2009 |
| Ntrust Infotech Ltd | Information & communication | 2019 |
| NUB Technologies Ltd | Manufacturing | 2021 |
| Nucleus Interactive Limited | Information & communication | 2026 |
| Nuflow Ltd | Information & communication | 2026 |
| Nurse Nicole Aesthetics Limited | Other services | 2021 |
| Nush Homefeast Ltd | Hospitality | 2025 |
| Nutrigreen Health Products Limited | Health & social care | 2004 |
| NVC Engineering Services Ltd | Professional & scientific | 2014 |
| NVS Asset Finance Ltd | Financial services | 2026 |
| Nyetech Limited | Manufacturing | 2015 |
| O'Dwyer Consulting Services Limited | Agriculture & fishing | 2024 |
| Oak & Stone Carpentry and Building Ltd | Construction | 2023 |
| Oak Farm Place Limited | Households | 2006 |
| Oakhurst Builders Limited | Construction | 2013 |
| Objective Intelligence Limited | Information & communication | 2026 |
| Occupational Psychiatry Limited | Health & social care | 2011 |
| Octaeder Ltd | Wholesale & retail | 2026 |
| OFF the Mark Limited | Hospitality | 2024 |
| OFF Watch Limited | Real estate | 2024 |
| OFFICE10 LLP | | 2012 |
| Offman (2010) Limited | Professional & scientific | 2010 |
| Old Plaw Hatch Farm Limited | Agriculture & fishing | 1980 |
| Olivers Executive Travel Limited | Other services | 2025 |
| Olivia and Alice Ltd | Information & communication | 2021 |
| Ollerton Property Group Ltd | Real estate | 2025 |
| Ollivere Limited | Professional & scientific | 2016 |
| Omeg Limited | Manufacturing | 1958 |
| Omega Enterprises Ltd | Financial services | 2025 |
| Omni Rental Properties Ltd | Real estate | 2024 |
| Omnia Functional Fitness Ltd | Arts & recreation | 2025 |
| ON the Piste Limited | Extraterritorial | 1987 |
| ON the Spectrum Ltd | Professional & scientific | 2018 |
| ON Your Bike Birmingham Limited | Wholesale & retail | 2017 |
| ON Your Bike Group Limited | Wholesale & retail | 2018 |
| ON Your Bike Holdings Limited | Wholesale & retail | 1992 |
| ON Your Bike Limited | Wholesale & retail | 2002 |
| ON Your Bike London Bridge Limited | Wholesale & retail | 2017 |
| Once Upon a Wish Events Limited | Arts & recreation | 2018 |
| Once Upon a Wish Parties Limited | Hospitality | 2023 |
| One Reach Digital Marketing Limited | Professional & scientific | 2020 |
| Onlaw.Net Limited | Professional & scientific | 2003 |
| Only Dogs Ltd | Other services | 2023 |
| Only Tools and Boxes (Property) Ltd | Real estate | 2021 |
| Only Tools and Boxes Ltd | Wholesale & retail | 2021 |
| Onsegelyezo Megoldasok Tanacsado ES Szolgaltato KFT Ltd | Information & communication | 2022 |
| Onyx Building Services Ltd | Extraterritorial | 2016 |
| Openchain Solutions Ltd | Information & communication | 2019 |
| Openterm Property Management Limited | Households | 1988 |
| OPG001 Limited | Real estate | 2016 |
| Ophthalmos Medical Care Ltd | Health & social care | 2022 |
| Optimal Card Ltd | Extraterritorial | 2017 |
| Option Hire Ltd | Administrative & support | 2021 |
| Optiva Holdings Limited | Financial services | 2025 |
| Opulent Productions Ltd | Arts & recreation | 2024 |
| Orca WS Ltd | Information & communication | 2023 |
| Orchard Cottage Property Limited | Real estate | 2017 |
| Orchard Nursery Plant Centre Limited | Wholesale & retail | 2016 |
| Oremus Gold Ltd | Wholesale & retail | 2021 |
| Organoid UK Ltd. | Administrative & support | 2019 |
| Origin & Co UK Ltd | Manufacturing | 2026 |
| Orlando.J Limited | Education | 2025 |
| Otterburn Venue Limited | Hospitality | 2019 |
| OUR London Ltd | Professional & scientific | 2012 |
| Oxted New Builds Ltd | Construction | 2025 |
| Oxted Property Limited | Real estate | 2022 |
| OXY Insight Ltd | Professional & scientific | 2015 |
| P a Solutions Limited | Extraterritorial | 2005 |
| P D Retails Limited | Wholesale & retail | 2023 |
| P&D Group Limited | Financial services | 2025 |
| P.M.R. Technology Limited | Wholesale & retail | 2002 |
| Paglia E Fieno Limited | Hospitality | 2015 |
| Paice Group Limited | Real estate | 1960 |
| Palmco Limited | Information & communication | 2014 |
| Panda Optics Ltd | Wholesale & retail | 2015 |
| Pandey and Sons Properties Limited | Construction | 2025 |
| Pandey Brothers Properties Limited | Real estate | 2025 |
| Pandey Brothers Restaurant Ltd | Hospitality | 2025 |
| Pano Steel Construct Ltd | Manufacturing | 2024 |
| Parafix World Trade Ltd | Financial services | 2025 |
| Paragonimperium Ltd | Wholesale & retail | 2024 |
| Paramind Medical Ltd | Health & social care | 2025 |
| Parchmore Investments Ltd. | Extraterritorial | 2008 |
| Passive House 4U Ltd | Manufacturing | 2026 |
| Pasta Nostra Limited | Hospitality | 2016 |
| Paterna Properties Limited | Professional & scientific | 2002 |
| Pats Garage Limited | Wholesale & retail | 2021 |
| Paul Build Ltd | Construction | 2008 |
| Paul Cruse Music Limited | Information & communication | 2010 |
| PAX Music Ltd | Information & communication | 2005 |
| PD Beardall Consulting Limited | Professional & scientific | 2012 |
| PDC3 Ltd | Financial services | 2017 |
| PDP Groundworks Ltd | Construction | 2025 |
| Peaceful Planet Human Rights Education | Education | 2017 |
| Peak Impex Limited | Wholesale & retail | 1999 |
| Peakcon Ltd | Wholesale & retail | 2024 |