| Novumtrade Ltd | Administrative & support | 2016 |
| Noyes Consulting Ltd | Public administration | 2023 |
| NP Broadcasting Limited | Information & communication | 2021 |
| NPA Legal Ltd | Professional & scientific | 2022 |
| Nplb Community Interest Company | Professional & scientific | 2024 |
| NPW Photo Media Ltd | Professional & scientific | 2025 |
| NRD Ventures Limited | Real estate | 2017 |
| NRG Arborists Ltd | Agriculture & fishing | 2024 |
| NRG Focus Limited | Professional & scientific | 2017 |
| NRO Electrical Limited | Manufacturing | 2024 |
| NRP Engineering Services Limited | Manufacturing | 2020 |
| NRS Property Holdings Ltd | Real estate | 2022 |
| Nrwl LLC Ltd | Information & communication | 2021 |
| NS Cargo Ltd | Transport & logistics | 2023 |
| NS Fabrications Limited | Manufacturing | 2010 |
| NS Haulage Limited | Transport & logistics | 2013 |
| NS Hospitality Ltd | Hospitality | 2026 |
| NS Logistics Solutions Limited | Transport & logistics | 2016 |
| NSA Consortium Ltd | Financial services | 2019 |
| NSB Flooring Ltd | Construction | 2025 |
| NSL Coaching Ltd | Education | 2021 |
| NSN Skin Ltd | Health & social care | 2025 |
| Nst&T Care Ltd | Health & social care | 2023 |
| NTN Properties Ltd | Real estate | 2021 |
| Ntpq Ltd | Education | 2018 |
| Ntwine Enterprises Limited | Professional & scientific | 2025 |
| Ntwine Limited | Wholesale & retail | 2020 |
| NU Ground Education Ltd | Administrative & support | 2026 |
| Nu-Con RMC Limited | Manufacturing | 2024 |
| Nubrick Developments Ltd | Construction | 2015 |
| Nufish Limited | Wholesale & retail | 2011 |
| Nulake Services Ltd | Health & social care | 2004 |
| Number 3 Whitby Limited | Real estate | 2024 |
| Nuptam Limited | Health & social care | 2019 |
| Nursery Covent Ltd | Real estate | 2012 |
| Nurshive Ltd | Administrative & support | 2023 |
| Nusa Analytics Ltd | Information & communication | 2023 |
| Nutrabaits International Limited | Manufacturing | 2017 |
| Nutrimind Life Ltd | Information & communication | 2025 |
| Nutriplanner Limited | Information & communication | 2005 |
| Nutrition Giants Ltd | Health & social care | 2025 |
| NV Qualifications Ltd | Education | 2015 |
| Nwaz Limited | Transport & logistics | 2019 |
| NXN Groundworks and Civils Ltd | Construction | 2023 |
| Nyky Drivers Ltd | Transport & logistics | 2015 |
| NZ Trans Logistics Limited | Transport & logistics | 2025 |
| O & P Construction Services (Holdings) Ltd | Financial services | 2024 |
| O & P Construction Services Limited | Construction | 1971 |
| O Fareed ROR FBA Limited | Wholesale & retail | 2021 |
| O Sharpe Holdings Limited | Financial services | 2026 |
| O&Kf Properties Ltd | Financial services | 2024 |
| O&M Medical Ltd | Health & social care | 2021 |
| O'Neills GAS Limited | Construction | 2022 |
| O.C.L. Properties Limited | Real estate | 2019 |
| O2 Ventilation Systems Ltd | Construction | 2018 |
| OAC Environmental Limited | Water & waste | 2016 |
| Oak Brook Motors Ltd | Wholesale & retail | 2020 |
| Oak Financial Solutions Ltd | Financial services | 2008 |
| Oak Tree Moorgate Limited | Health & social care | 2019 |
| Oakbrook Developments Limited | Professional & scientific | 1997 |
| Oakbrook Introductions Limited | Professional & scientific | 1998 |
| Oaken Lodge Developments Limited | Real estate | 2005 |
| Oakham Homes Limited | Real estate | 2015 |
| Oakley's Site Services Ltd | Construction | 2017 |
| Oakmont Building Contractors Limited | Construction | 2024 |
| Oakvilla Ltd | Real estate | 2026 |
| Oakwood Joinery Services (Sheffield) Limited | Construction | 2015 |
| Oasis Pet Products Ltd | Wholesale & retail | 2024 |
| Oasis Property Holdings Limited | Real estate | 2023 |
| Oasis Softdrinks Limited | Wholesale & retail | 2010 |
| Oasis Trade Ltd | Wholesale & retail | 2025 |
| OB Plumbing and Heating (South Yorkshire) Ltd | Construction | 2025 |
| Obaa YAA Papabi Groceries Ltd | Wholesale & retail | 2025 |
| Occasional Recursion Ltd | Information & communication | 2022 |
| Ocean Colour Developments Ltd | Real estate | 2021 |
| Oconnor Broadcast Engineering Services Ltd | Information & communication | 2025 |
| Octavo Gate Limited | Information & communication | 2008 |
| Octopus Campers Ltd | Manufacturing | 2023 |
| Odmarketingu.Pl Ltd | Professional & scientific | 2026 |
| ODS Motors Ltd | Wholesale & retail | 2026 |
| Odyssey Coaching Limited | Arts & recreation | 2024 |
| Oepe Ltd | Information & communication | 2024 |
| OFF the Beaten Path Ltd | Wholesale & retail | 2025 |
| Offhood Limited | Wholesale & retail | 2025 |
| Office 106 Limited | Wholesale & retail | 2022 |
| Offplan Dwellings Ltd | Extraterritorial | 2019 |
| Offset Strength Ltd | Manufacturing | 2024 |
| Offshore Works Limited | Professional & scientific | 2018 |
| Ofibo TF Ltd | Construction | 2022 |
| OFK Visa Consultancy Ltd | Professional & scientific | 2025 |
| OH Rendering Ltd | Construction | 2023 |
| Ohana Cooke Ltd | Real estate | 2024 |
| Ohsca Ltd | Information & communication | 2024 |
| OK YAY Ltd | Hospitality | 2022 |
| OK22 Ltd | Hospitality | 2021 |
| Okaeri Limited | Construction | 2022 |
| Oksidia Ltd | Information & communication | 2024 |
| Old Brewers Court RTM Company Limited | Households | 2024 |
| Old Flatts Farm Canine Lodge Ltd | Other services | 2024 |
| Old Flatts Farm Feline Retreat Ltd | Other services | 2024 |