| Nogar Ltd | Information & communication | 2015 |
| Nonnaromas Ltd | Hospitality | 2022 |
| Norsemen Courier Service Ltd | Transport & logistics | 2025 |
| North to South Rentals Ltd | Real estate | 2019 |
| Northsouth Design and Marketing Ltd | Information & communication | 2017 |
| Northwick Storage Limited | Transport & logistics | 2015 |
| Nostalgia Works Ltd | Professional & scientific | 1999 |
| NOT Under One Roof Ltd | Professional & scientific | 2013 |
| Noticepride Holdings Limited | Real estate | 2018 |
| Noticepride Limited | Information & communication | 1991 |
| Novomium Enterprises Ltd | Administrative & support | 2015 |
| NPS Trading Ltd | Wholesale & retail | 2020 |
| NPS UK Property Ltd | Real estate | 2025 |
| NSC Installations Limited | Construction | 2012 |
| NT Nails Rayleigh Limited | Other services | 2024 |
| Nursly Ltd | Information & communication | 2026 |
| Nvss Investments Ltd | Real estate | 2019 |
| NXT GEN Energy Ltd | Construction | 2022 |
| NXT GEN Externals Limited | Construction | 2020 |
| NXT GEN Futures Ltd | Construction | 2023 |
| NXT GEN Limited | Financial services | 2024 |
| NXT GEN Metachain Ltd | Administrative & support | 2023 |
| NXT GEN Scaffolding Limited | Construction | 2020 |
| NXT GEN TEK Recruitment Limited | Administrative & support | 2023 |
| NXT Generation Homes Limited | Real estate | 2018 |
| Nxtgen TEK Ltd | Administrative & support | 2023 |
| Oakborne Research Limited | Information & communication | 2016 |
| Oakenhurst Aircraft Services Limited | Manufacturing | 1989 |
| Oakenhurst Holdings Ltd | Financial services | 2022 |
| Occazions Flowers Limited | Wholesale & retail | 2024 |
| Octacet Limited | Wholesale & retail | 2024 |
| Octopus Express Group Limited | Wholesale & retail | 2012 |
| Odfb Holdings Limited | Financial services | 2020 |
| ODP Waste Management Ltd | Water & waste | 2026 |
| OEB Building Services Ltd | Construction | 2020 |
| Office Law 1 Limited | Professional & scientific | 2019 |
| Office Life Solutions Ltd | Manufacturing | 2010 |
| OJ Electrical Services Ltd | Construction | 2025 |
| OL Consultancy Ltd | Information & communication | 2025 |
| Old Chapel Clothing Ltd | Wholesale & retail | 2015 |
| Old Geezer Ltd | Manufacturing | 2022 |
| Ollie Glass Ltd | Professional & scientific | 2017 |
| OMG Event Hire Ltd | Arts & recreation | 2021 |
| Omni Lofts Ltd | Construction | 2025 |
| Omnia Education Limited | Education | 2019 |
| Omnia Sports Community Limited | Education | 2023 |
| Omnia Sports Education Limited | Construction | 2021 |
| Omnia Sports Group Limited | Financial services | 2024 |
| Omnia Sports Media Limited | Administrative & support | 2022 |
| Omnia Sports Services Limited | Information & communication | 2023 |
| Omnirocker Limited | Manufacturing | 2020 |
| Omtech Services Limited | Construction | 2018 |
| ON Plan Group Ltd | Manufacturing | 2011 |
| ON the Square Hertford Ltd | Hospitality | 2021 |
| One Stop Scouting Investments Limited | Financial services | 2022 |
| Online Venture Partners Limited | Professional & scientific | 2011 |
| Onsite Broadcast Ltd | Information & communication | 2025 |
| Onsite Facade Solutions Limited | Construction | 2020 |
| Ontime Onslow Services Ltd | Construction | 2014 |
| Onyl Lohr Holdings Limited | | 1962 |
| Open Door IFA Ltd | Financial services | 2006 |
| Opsafe Ltd | Mining & quarrying | 2021 |
| Optima.Ai Testing Ltd | Information & communication | 2025 |
| Optimise Your AGE Limited | Health & social care | 2024 |
| Orbit Financial Services Ltd | Financial services | 2015 |
| Orderly Services Ltd | Professional & scientific | 2025 |
| Ordway Ventures Ltd | Administrative & support | 2012 |
| Origami Holdings Limited | Professional & scientific | 2022 |
| Origin Film & Television Ltd | Information & communication | 2020 |
| Orion Bookkeepers Ltd | Professional & scientific | 2026 |
| Osburn’S Butchers Ltd | Wholesale & retail | 2021 |
| Osler Property Law Limited | Professional & scientific | 2024 |
| OTB Reactive Services Ltd | Water & waste | 2021 |
| OUM Station News Ltd | Wholesale & retail | 2021 |
| OUT in London Media Ltd | Professional & scientific | 2018 |
| OUT of Nowhere Limited | Arts & recreation | 2016 |
| Outstanding Leaders Ltd | Construction | 2010 |
| Outtaspace Construction Ltd | Construction | 2020 |
| OWL and Monkey Pink Tea Ltd | Wholesale & retail | 2024 |
| Owmax Ltd | Health & social care | 2024 |
| Oyster Creek Marina Ltd | Manufacturing | 2024 |
| P & W Homes Ltd | Real estate | 2023 |
| P G Groundcare Ltd | Administrative & support | 2015 |
| P R Auto Group Limited | Wholesale & retail | 2017 |
| P Simon Import Export Services Ltd | Transport & logistics | 2010 |
| P&A (Essex) Ltd | Real estate | 2024 |
| P.G.M. Carpentry Contractors Limited | Construction | 2004 |
| P.G.M. Carpentry Holdings Limited | Financial services | 2021 |
| PAB Business Solutions Ltd | Administrative & support | 2010 |
| Padel Tripper Ltd | Administrative & support | 2024 |
| Paint and Piercing Limited | Other services | 2023 |
| Paint Repair Solutions Ltd | Wholesale & retail | 2023 |
| Palmerkidneycare Ltd | Health & social care | 2011 |
| Pan-Web Limited | Wholesale & retail | 2017 |
| Pannbrook Properties Ltd | Real estate | 2026 |
| Parade Walk (Solar) Freehold Company Limited | Households | 2015 |
| Paradine Kane Property Ltd | Households | 2023 |
| Parker Pointing Limited | Construction | 2015 |
| Parkes Media Group Ltd | Professional & scientific | 2024 |
| Particulate Limited | Professional & scientific | 2022 |