| Nexus Mechanical & Plumbing Services (South East) Ltd | Construction | 2025 |
| NFB DE Korczak Limited | Real estate | 2015 |
| Nichola Bruce Archive & Production Limited | Professional & scientific | 2004 |
| Nicky Percival Limited | Arts & recreation | 2015 |
| Night Owls Cave Ltd | Wholesale & retail | 2023 |
| Night School Limited | Information & communication | 2017 |
| Niltex Ltd | Information & communication | 2025 |
| Nixey-Cushing Retail Consulting Limited | Wholesale & retail | 2009 |
| NMZ Construction Limited | Construction | 2025 |
| NO 26 Priory Avenue Management Co Limited | Households | 2017 |
| Noahs Goat Ltd | Wholesale & retail | 2024 |
| Noble Ground Management Ltd | Professional & scientific | 2016 |
| Northridge Sales and Restoration Limited | Wholesale & retail | 2018 |
| Novanax Wholesale Ltd | Wholesale & retail | 2026 |
| Nowhere Fast Ltd | Professional & scientific | 2022 |
| Nowy UK Limited | Wholesale & retail | 2019 |
| Nphora Ltd | Information & communication | 2014 |
| Nrjtech Ltd | Information & communication | 2018 |
| Nukhbat AL Iraq for Information Technology and Software Ltd | Administrative & support | 2025 |
| Nulevel Limited | Wholesale & retail | 2020 |
| Nurseflex Ltd | Administrative & support | 2026 |
| Nursing Hands Limited | Health & social care | 2025 |
| O'Sullivans Snooker Limited | Arts & recreation | 2010 |
| Oak Verde Carpentry Ltd | Construction | 2022 |
| Oakbridge Accountants Ltd | Wholesale & retail | 2025 |
| Oakhurst Homes & Property Limited | Construction | 2017 |
| Oaklands (Sedlescombe) Limited | Extraterritorial | 2013 |
| Oakley Services 1066 Limited | Construction | 2018 |
| Oakly Holdings Limited | Real estate | 2015 |
| Oakprism Ltd | Other services | 2025 |
| Oaks Martial Arts Ltd | Other services | 2012 |
| Oars Ltd | Information & communication | 2026 |
| OB Barker Construction Ltd | Construction | 2025 |
| OB1 Robotics Limited | Professional & scientific | 2014 |
| Oborne Asset Management Limited | Professional & scientific | 2021 |
| Octane Studios Limited | Information & communication | 2026 |
| Odysseuscapital Ltd | Wholesale & retail | 2022 |
| OFF Grid Developments Ltd | Construction | 2024 |
| Ohmj Limited | Wholesale & retail | 2019 |
| Ohps & FM Trading Co Ltd | Wholesale & retail | 2013 |
| OJ Liquor Co Ltd | Real estate | 2014 |
| Old Bean Studios Ltd | Information & communication | 2024 |
| Old Halloway House Management Company Limited | Health & social care | 1999 |
| Old Town Osteopathy Ltd | Health & social care | 2021 |
| Old Town Sweet Shop Limited | Other services | 2018 |
| OLI Kellett Ltd | Professional & scientific | 2013 |
| Omnira Commerce Ltd | Wholesale & retail | 2026 |
| ON Track Recruitment Ltd | Administrative & support | 2000 |
| One Wellington Square Management Company Limited | Households | 2013 |
| ONE4LUCK Limited | Professional & scientific | 2015 |
| Onguard Protection Security Ltd | Administrative & support | 2025 |
| Onlinetoget Ltd | Administrative & support | 2026 |
| Onpoint Staff Recruitment Ltd | Administrative & support | 2021 |
| Ontario UK Partnership Ltd | Wholesale & retail | 2024 |
| Onyourhike Limited | Extraterritorial | 2015 |
| Open Design Limited | Professional & scientific | 2013 |
| Open Door Communications Ltd | Administrative & support | 2008 |
| OPS Plastering and Property Services Ltd | Construction | 2026 |
| Optology Limited | Extraterritorial | 2009 |
| Orchard Lodge Property Developments Ltd | Real estate | 2025 |
| Orderdash Ltd | Wholesale & retail | 2025 |
| ORE Mini Market Ltd | Wholesale & retail | 2023 |
| Orna Ross Publications & Programmes Ltd | Information & communication | 2020 |
| Oryanacare Ltd | Administrative & support | 2017 |
| Osborne Energy Funding Solutions Limited | Other services | 2021 |
| Osborne Energy Holdings Ltd | Financial services | 2019 |
| Osborne Energy Limited | Administrative & support | 1996 |
| Osborne House (Littlestone) Limited | Hospitality | 2004 |
| Osity Limited | Administrative & support | 2022 |
| Osky Limited | Wholesale & retail | 2025 |
| Ossomed Ltd | Wholesale & retail | 2022 |
| OUR Building Design Limited | Professional & scientific | 2018 |
| OUR Pioneer Care Ltd | Administrative & support | 2015 |
| OUR Small Planet Ltd | Administrative & support | 2024 |
| Outdoorsman Supplies Limited | Wholesale & retail | 2013 |
| Oval Wealth Partners Limited | Financial services | 2014 |
| Ovimit Logistics Limited | Transport & logistics | 2022 |
| Oxygen O2 Hbot Limited | Wholesale & retail | 2023 |
| Oyster Creatives LLP | | 2017 |
| Ozgu Investment Hastings Ltd | Real estate | 2026 |
| P B Brickwork Limited | Construction | 2014 |
| P H Motors Limited | Wholesale & retail | 2003 |
| P J Clifford Ltd | Construction | 2012 |
| Pada Hanlon Limited | Real estate | 2016 |
| Pada Hanlon Portfolio B Limited | Real estate | 2019 |
| Padgham Consulting Ltd | Professional & scientific | 2024 |
| Pain Free Movement Limited | Other services | 2019 |
| Painted Matter Ltd | Construction | 2024 |
| Palace Building Services Ltd | Construction | 2015 |
| Palace Court Commercial Property Limited | Construction | 2021 |
| Panda Technologies Limited | Information & communication | 2015 |
| Pandora's Boxers Ltd | Wholesale & retail | 2017 |
| Panic Apps (UK) Limited | Information & communication | 2016 |
| Paradigm Consultancy Limited | Information & communication | 2017 |
| Paradise on Sea Ltd | Hospitality | 2025 |
| Paramount Medical Solutions Limited | Manufacturing | 2005 |
| Parcelboxes Installed Limited | Households | 2017 |
| Parcelboxes Limited | Households | 2017 |
| Parchment Trust | Health & social care | 2000 |
| Paren Ltd | Information & communication | 2018 |