| New Road Property Limited | Real estate | 2002 |
| Newgnt Limited | Information & communication | 2018 |
| Newtryx Limited | Information & communication | 2017 |
| Next Way Station Ltd | Financial services | 2023 |
| Nick Samuels Private Travel Limited | Administrative & support | 2022 |
| Nightingale Private Limited Company Ltd. | Financial services | 2017 |
| Nizatto Digital Limited | Administrative & support | 2010 |
| NJC Projects Limited | Information & communication | 2021 |
| NLS Services Limited | Transport & logistics | 2022 |
| NM Quanta Solutions Limited | Professional & scientific | 2015 |
| Nolabex Ltd | Wholesale & retail | 2020 |
| Noor 24 Limited | Wholesale & retail | 2024 |
| Nordtek Packaging Ltd | Other services | 2013 |
| North Drive Maresfield Management Company Limited | Households | 2022 |
| Northlands H.H Limited | Health & social care | 2010 |
| Norwood Scaffolding and Roofing Limited | Construction | 2015 |
| NOT Just Compliance Limited | Professional & scientific | 2025 |
| Notable Holdings Limited | Extraterritorial | 2025 |
| Noundel Ltd | Information & communication | 2022 |
| Novagas (LPG) Limited | Wholesale & retail | 2014 |
| Now-Bee Limited | Information & communication | 2017 |
| Nsdpm Solution Ltd | Administrative & support | 2019 |
| Nurettin Yorulmaz Ltd | Hospitality | 2014 |
| Nutley Hall | Health & social care | 1966 |
| Nutley Motor Services Limited | Wholesale & retail | 2003 |
| Nutley Social Club Ltd | Other services | 2004 |
| Nutley Tennis & Squash Club CIC | Arts & recreation | 2020 |
| Nutrismartworld Limited | Wholesale & retail | 2012 |
| Oakheart Films Ltd | Information & communication | 2011 |
| Oakhyrst Homes Limited | Administrative & support | 2011 |
| Oakmor Properties Ltd | Construction | 2025 |
| Oakridge House Management Company Ltd | Households | 2018 |
| Oakwood Close Residents Management Company Limited | Households | 2017 |
| Oakwood Finishing Limited | Construction | 1998 |
| Oakwood Park Polo Club Limited | Other services | 2005 |
| Oasis Therapy Ltd | Health & social care | 2024 |
| Obsesseduk Ltd | Wholesale & retail | 2023 |
| Obsidian Partitioning Limited | Financial services | 2015 |
| Odab Contracts Ltd | Real estate | 2012 |
| OFF the Wall Entertainment Ltd. | Education | 2015 |
| Old Crown Place Management Company Ltd | Households | 2022 |
| Old Lodge Property Management Limited | Professional & scientific | 1996 |
| Old Spot Farm Limited | Extraterritorial | 2005 |
| Oldlands Estate Company Limited | Households | 1952 |
| Oleum Controls Limited | Professional & scientific | 2007 |
| Olive House Residents Association Limited | Real estate | 2003 |
| Olivet Assembly | Education | 2015 |
| Olivet College | Education | 2006 |
| OMM Lebanese (Uckfield) Ltd | Hospitality | 2021 |
| ON Electrical Services Ltd | Professional & scientific | 2019 |
| One Central System Limited | Information & communication | 2018 |
| One Green LAB Ltd | Wholesale & retail | 2015 |
| Onozoom Ltd | Professional & scientific | 2017 |
| Onsongmusic Ltd. | Arts & recreation | 2017 |
| Onward-Ker-Uk Ltd | Financial services | 2022 |
| Op-Va Ltd | Financial services | 2021 |
| Oprea V Detailing Ltd | Wholesale & retail | 2025 |
| Oracle Fluid Management Systems Ltd | Wholesale & retail | 2016 |
| Orchard Place Maresfield Ltd | Households | 2018 |
| Orgasmic Foods Limited | Wholesale & retail | 1996 |
| Oryta Ltd | Financial services | 2021 |
| Osborn Construction Limited | Construction | 2024 |
| Osborn Homes Limited | Real estate | 1993 |
| Oshanti Restaurant Limited | Hospitality | 2025 |
| Osmonds Timber Limited | Agriculture & fishing | 2016 |
| Osprey Measurement Systems International Ltd | Manufacturing | 2016 |
| Osprey Measurement Systems Ltd | Financial services | 2019 |
| Oteka Music Ltd | Arts & recreation | 2020 |
| OUR Futures and Options Ltd | Financial services | 2025 |
| Ozzmium Limited | Wholesale & retail | 2012 |
| P P Estates Ltd. | Wholesale & retail | 1999 |
| P S Technology Consultants Limited | Information & communication | 2003 |
| Padel Pros Ltd | Construction | 2022 |
| Paice Engineering Ltd | Professional & scientific | 2020 |
| Palanki Ltd | Wholesale & retail | 2011 |
| Panda Publications Ltd | Information & communication | 2017 |
| Pappco Ltd | Information & communication | 2014 |
| Paradisii Software Solutions Limited | Information & communication | 2005 |
| Parfitt Cresswell Corporate Trustees Limited | Professional & scientific | 2023 |
| Parfitt Cresswell Limited | Professional & scientific | 2008 |
| Parfitt Cresswell Trust Corporation Limited | Professional & scientific | 2018 |
| Park Fisheries Limited | Arts & recreation | 2019 |
| Parker Building Solutions Ltd | Construction | 2026 |
| Parris Wolfe Limited | Real estate | 2017 |
| Partners in Flow Limited | Professional & scientific | 2001 |
| Pastels Floral Art & Design Limited | Arts & recreation | 1987 |
| Pat&Er Ltd | Construction | 2014 |
| Paul André Jewellers Ltd | Wholesale & retail | 2012 |
| Paul Hawkins GAS Ltd | Construction | 2021 |
| Paws 'N' Claws (Sussex) Limited | Wholesale & retail | 2004 |
| Payassist Limited | Professional & scientific | 2014 |
| Paygate Wood Limited | Extraterritorial | 2015 |
| Paynes Heating and Plumbing Services Limited | Construction | 1990 |
| PDM Logistics Ltd | Transport & logistics | 2025 |
| PDO Ltd | Professional & scientific | 2012 |
| Peachy Clean Cleaning Company Ltd | Administrative & support | 2026 |
| Pear Tree Well Limited | Water & waste | 2004 |
| PEBBLES157 Ltd | Professional & scientific | 2022 |
| Peerland (Management) Limited | Administrative & support | 2006 |
| Penda Studios Limited | Professional & scientific | 2021 |