| Norton Grange Limited | Construction | 2020 |
| Norway Lane Limited | Real estate | 2019 |
| Norwood Court Residents Company Limited | Real estate | 1992 |
| Norwoods Outsourcing Ltd | Administrative & support | 2017 |
| Nosi Baking Limited | Hospitality | 2025 |
| Noted Studio Ltd | Professional & scientific | 2025 |
| Notso BAO UK Ltd | Hospitality | 2023 |
| Notso Festivals Ltd | Hospitality | 2023 |
| Notso Sushi Ltd | Hospitality | 2010 |
| Nottingham Wine Buying Group Ltd. | Extraterritorial | 2004 |
| Nova Build (Sussex) Ltd | Construction | 2024 |
| Nova Homes (Sussex) Ltd | Construction | 2025 |
| Nova HUT Ltd | Hospitality | 2025 |
| Novawash Ltd | Other services | 2018 |
| Noviom Developments Limited | Construction | 2020 |
| Noviom Labs Limited | Information & communication | 2018 |
| Novium Limited | Professional & scientific | 2012 |
| Noviun Design Ltd | Professional & scientific | 2024 |
| Noviun Limited | Professional & scientific | 1996 |
| Novus Sourcing Limited | Wholesale & retail | 2023 |
| NOX Properties Ltd | Real estate | 2025 |
| NP Wilson Ltd | Wholesale & retail | 2022 |
| NSR Fleet Support Ltd | Professional & scientific | 2024 |
| NU Media Group Ltd | Professional & scientific | 2022 |
| NU Media Hub Limited | Professional & scientific | 2019 |
| Nucleo Group Limited | Construction | 2017 |
| Nudge Works XR Ltd | Information & communication | 2025 |
| Nultree Limited | Administrative & support | 1980 |
| Nurture Flow Ltd | Professional & scientific | 2019 |
| Nutbourne Construction Ltd | Construction | 2003 |
| Nutbourne Veterinary Centre Limited | Professional & scientific | 2024 |
| NWF Holdco Limited | Financial services | 2025 |
| NXA Logistics Ltd | Transport & logistics | 2025 |
| NYE Group Limited | Financial services | 2020 |
| Nyton House Limited | Health & social care | 2016 |
| O'Brien Homes Limited | Construction | 1996 |
| O.K. Computers Limited | Information & communication | 1983 |
| O2 Exhibitions Ltd | Administrative & support | 2003 |
| Oakdene Builders (Chidham) Limited | Construction | 2008 |
| Oakdene Gardens Management Company Limited | Households | 2017 |
| Oakhurst Farm Sidlesham Limited | Agriculture & fishing | 2018 |
| Oakland (Littlehampton) Limited | Health & social care | 1994 |
| Oakland Court Limited | Health & social care | 1997 |
| Oakland Limited | Construction | 1981 |
| Oaklands Communications Limited | Professional & scientific | 2016 |
| Oaklands Funeral Service Limited | Other services | 2012 |
| Oaklands Landscapes & Paving Ltd | Administrative & support | 2026 |
| Oaklands Pavilion Ltd | Hospitality | 2019 |
| Oaklands Workshop Limited | Administrative & support | 2015 |
| Oaksdynamics Events Ltd | Construction | 2019 |
| Oaktree Cottages Holdings Ltd | Real estate | 2021 |
| Oakway Secure Limited | Administrative & support | 2026 |
| Oakwood School | Education | 2004 |
| Oatlands Drive Limited | Real estate | 2008 |
| OBE Vision Ltd | Administrative & support | 2011 |
| Obtrada Limited | Professional & scientific | 2019 |
| OBX Gym Ltd | Arts & recreation | 2021 |
| Occupational Health Professionals LLP | | 2007 |
| Ocean FRY Group Ltd | Hospitality | 2026 |
| Ocean Ready Ltd | Manufacturing | 2017 |
| Ocean View Diving Services Limited | Wholesale & retail | 2004 |
| Octavia LDN Limited | Wholesale & retail | 2020 |
| Odin Professional Services Ltd | Professional & scientific | 2025 |
| Odin’S Marketing Strategies Ltd | Extraterritorial | 2024 |
| Odyssey Contracting Ltd | Manufacturing | 2020 |
| OE Global Parts UK Limited | Wholesale & retail | 2020 |
| Office Box Limited | Health & social care | 2017 |
| Office N1 Limited | Real estate | 2013 |
| Office World Ltd | Wholesale & retail | 2003 |
| Offsite Hire Ltd | Wholesale & retail | 2018 |
| OGW Event Catering Ltd | Hospitality | 2017 |
| OHB (Developments) Ltd | Construction | 2017 |
| Ohns Service Limited | Health & social care | 2015 |
| Ohsogreengardens Ltd | Water & waste | 2025 |
| Oikos Associates Limited | Construction | 2021 |
| Ojee Limited | Real estate | 2023 |
| OKB Medical Limited | Wholesale & retail | 2002 |
| Okla Homes Limited | Real estate | 2015 |
| Old Bakery Mews (Hampton) Management Ltd | Households | 2022 |
| Old Bakery Mews (Management) Limited | Households | 1987 |
| Old Dog Aviation Limited | Professional & scientific | 2015 |
| Old Haven Developments Limited | Construction | 2023 |
| Old Haven Limited | Financial services | 2025 |
| Old Market House Limited | Administrative & support | 2010 |
| Old Moat Construction Ltd | Construction | 2024 |
| Old Park Farm (Bosham) Limited | Agriculture & fishing | 2004 |
| Old Red Lion Welham Limited | Hospitality | 2025 |
| Old School Pubs Ltd | Hospitality | 2019 |
| Old Smithy Limited | Hospitality | 2025 |
| Oldlands Farm Promotions Limited | Professional & scientific | 2023 |
| Oldlands Properties Limited | Construction | 2019 |
| Oldwick Farm Limited | Administrative & support | 2000 |
| Olga Genc Beauty Ltd | Other services | 2024 |
| Olive Weddings Limited | Administrative & support | 2012 |
| Oliver Evans Ltd | Professional & scientific | 2020 |
| Olivia Creber Ltd | Professional & scientific | 2016 |
| Omorita Ltd | Health & social care | 2023 |
| OMS Chichester Ltd | Manufacturing | 2014 |
| OMS Marine Parts Ltd | Manufacturing | 2021 |
| ON Cloud 9 Accounting Ltd | Professional & scientific | 2014 |