| Noryxa UK Ltd | Wholesale & retail | 2025 |
| Noviqa Ltd | Administrative & support | 2012 |
| NRI Automotive Ltd | Wholesale & retail | 2026 |
| Nsonash Limited | Wholesale & retail | 2025 |
| Nugent (Holdings) Limited | Professional & scientific | 2013 |
| Nugent Estate and Farm Limited | Agriculture & fishing | 2019 |
| Nugent Estates Trading Company Limited | Financial services | 1995 |
| Nuskme Limited | Wholesale & retail | 2024 |
| O Denvir Construction Ltd | Construction | 2018 |
| O'Prey Building Surveying Limited | Professional & scientific | 2025 |
| O'Prey Developments Limited | Construction | 2003 |
| Oaklands Avenue Property Management Ltd | Households | 2017 |
| Oasis Village Trust | Hospitality | 2008 |
| OEB Consulting Ltd | Professional & scientific | 2026 |
| Oeiliam Limited | Wholesale & retail | 2025 |
| OFL Properties Ltd | Real estate | 2021 |
| OH Good Limited | Wholesale & retail | 2024 |
| Oldfield Farm Ltd | Hospitality | 2024 |
| Oleg Ozoling Limited | Wholesale & retail | 2025 |
| Olive by Cafolla's Ltd | Hospitality | 2023 |
| Oliver's Coffee Deli Belmont Ltd | Hospitality | 2022 |
| Olympus LAB Ltd | Information & communication | 2025 |
| Omak Agencies Limited | Wholesale & retail | 1990 |
| OMB Retail Limited | Wholesale & retail | 2018 |
| Omphacite Limited | Wholesale & retail | 2025 |
| One Quantum Group Ltd | Administrative & support | 2026 |
| One Thing Ltd | Wholesale & retail | 2022 |
| Onebay Amazing Limited | Wholesale & retail | 2025 |
| Oneokema Limited | Wholesale & retail | 2025 |
| Only Plant Based Foods International Ltd | Wholesale & retail | 2019 |
| Onseng Limited | Wholesale & retail | 2025 |
| Ontime Wish Limited | Wholesale & retail | 2025 |
| Oocelot Ltd | Construction | 2025 |
| Opal Horizon Ltd | Wholesale & retail | 2025 |
| Openhouse Enterprises Limited | Hospitality | 2007 |
| OPH HK Limited | Wholesale & retail | 2025 |
| Optimx Pro Ltd | Information & communication | 2024 |
| Optomise Hearing Ltd | Wholesale & retail | 2017 |
| Optomise Limited | Wholesale & retail | 2001 |
| Orange Plain Limited | Wholesale & retail | 2023 |
| Orange Tree House Limited | Hospitality | 2015 |
| Orcas Systems Ltd | Construction | 1997 |
| Oriental Express NI Ltd | Hospitality | 2024 |
| Origin Gymnastics Limited | Arts & recreation | 2022 |
| Ormeau Holdings Limited | Financial services | 2024 |
| Orr's Travel Limited | Administrative & support | 1983 |
| Orthodocs Ltd | Wholesale & retail | 2000 |
| Orthodox Romanian Parish Ltd | Other services | 2023 |
| Orthokeratology Limited | Health & social care | 2026 |
| Oscars Coffee Dock Ltd | Hospitality | 2016 |
| Ossia Music Ltd | Administrative & support | 2003 |
| OUR Earth Ltd | Wholesale & retail | 2018 |
| Outdoor Revival Ltd | Wholesale & retail | 2026 |
| Ouyang Technology Co., Ltd | Wholesale & retail | 2024 |
| Ovenpro Service Ltd | Administrative & support | 2017 |
| Overdene Newtownards Limited | Real estate | 2002 |
| P & E Catering Limited | Hospitality | 2013 |
| P J Hughes Plumbing & Heating Ltd | Construction | 2005 |
| P Lappin Construction Ltd | Construction | 2022 |
| P M Distribution Limited | Wholesale & retail | 2003 |
| P M Plant Hire (2015) Ltd | Administrative & support | 2015 |
| P&F Eakin 2014 Limited | Professional & scientific | 2014 |
| P.B.C. Aviation Limited | Manufacturing | 2015 |
| P.R. Golf Distribution Limited | Other services | 2005 |
| Paddock Management Company (Comber) Limited - the | Households | 2004 |
| Paige Jones Limited | Wholesale & retail | 2026 |
| Paintworks (N.I.) LLP | | 2014 |
| Palatine Trust-The | Professional & scientific | 1997 |
| Panshiyan Limited | Wholesale & retail | 2024 |
| Paperback Down Ltd | Wholesale & retail | 2022 |
| Parfix Equipment Company Limited | Wholesale & retail | 1988 |
| Parkview Service Station Ltd | Wholesale & retail | 2011 |
| Part 1 Productions Limited | Information & communication | 2025 |
| Patrick Hughes Limited | Construction | 2016 |
| Patrick LLO Limited | Wholesale & retail | 2025 |
| Patton's Bakery Limited | Manufacturing | 2011 |
| Paul Arthurs Investments Ltd | Real estate | 2024 |
| Paul Bavin Ltd | Wholesale & retail | 2025 |
| Paul Blaney Motors Ltd | Wholesale & retail | 2015 |
| Paul Chambers Quantity Surveyors Ltd | Professional & scientific | 2015 |
| Paul Flynn Physiotherapy Limited | Health & social care | 2016 |
| Paul Linden Ltd | Wholesale & retail | 2023 |
| Paulnicholasderetail Limited | Wholesale & retail | 2025 |
| Pavotmargueritte Ltd | Hospitality | 2024 |
| Paweloski Limited | Wholesale & retail | 2025 |
| Pazgolf Ltd | Information & communication | 2025 |
| Pdytadejederetail Ltd | Wholesale & retail | 2025 |
| Pdytadwoden Ltd | Wholesale & retail | 2025 |
| Pearl Heel Co., Ltd | Hospitality | 2024 |
| PEB Enterprises Ltd | Real estate | 2003 |
| Pedestal Supplies Ltd | Wholesale & retail | 2026 |
| Pengqian Shop Limited | Wholesale & retail | 2025 |
| Peninsula Care Services (NI) Ltd | Administrative & support | 2010 |
| Peninsula Electrical Limited | Construction | 2019 |
| Peninsula Enterprises Ltd | Wholesale & retail | 2026 |
| Peninsula Fleet Management Ltd | Administrative & support | 2021 |
| Peninsula Stable Minds C.I.C. | Education | 2024 |
| Penn Fencing Limited | Manufacturing | 2015 |
| Penni Holdings (N.I.) Ltd | Financial services | 2025 |
| Pentiot AI Ltd | Information & communication | 2025 |