| Nutt Travel Holdings Limited | Financial services | 2025 |
| NW ENT Care Ltd | Health & social care | 2022 |
| O&E Mcatamney Retail Ltd | Wholesale & retail | 2014 |
| O'Connells Garage Ltd | Wholesale & retail | 2003 |
| O'Kane Developments (NI) Ltd | Construction | 2006 |
| O2 North West Clinics Limited | Health & social care | 2024 |
| Oakfield Mews Management Services Company Limited | Households | 2001 |
| Oakleaf Worldwide Ltd | Administrative & support | 2015 |
| Oakmore Developments | Construction | 2003 |
| Oakview (Cookstown) Management Company Limited | Households | 2017 |
| OBG Engineering NI Ltd | Manufacturing | 2024 |
| OJM Tools Limited | Administrative & support | 2012 |
| OJQ Limited | Professional & scientific | 2016 |
| Olar Commerce Ltd | Wholesale & retail | 2023 |
| Old Corn Mill Management Co Ltd | Households | 2018 |
| Old Market Vans (Coleraine) Ltd | Wholesale & retail | 2026 |
| Old Mart Management Company Limited- the | Households | 2009 |
| Old School Management (NI) Limited | Households | 2003 |
| Oliver Transport Services Ltd | Transport & logistics | 1988 |
| Olivia's Haven Ltd | Wholesale & retail | 2019 |
| Ontrax Equipment Ltd | Wholesale & retail | 2022 |
| Orchard (Coleraine) Management Company Limited the | Households | 2009 |
| Ordo Consultants Limited | Professional & scientific | 2025 |
| Oriental Development Holdings Ltd | Financial services | 2018 |
| Outhill Holdings Ltd | Hospitality | 2023 |
| Overstate Ltd | Wholesale & retail | 2025 |
| Oyster Community Press CIC | Arts & recreation | 2014 |
| P & H Services (Mechanical) Limited | Construction | 2003 |
| P.V.C. Direct Limited | Construction | 1999 |
| PAL Associates (Services) Ltd | Professional & scientific | 2017 |
| PAM Building Services Ltd | Construction | 2019 |
| Park Manor Ballymena Management Company Limited | Households | 2007 |
| Parkside Court Services Ltd | Households | 2007 |
| Partsdoc Ltd | Wholesale & retail | 2010 |
| Patton Marine NI Ltd | Manufacturing | 2024 |
| Paul D Thompson Solicitors Limited | Professional & scientific | 2019 |
| Paul Etherson Construction Ltd | Construction | 2025 |
| Paul Taylor & Company Limited | Professional & scientific | 2024 |
| Payrunner Ltd | Professional & scientific | 2016 |
| Pebbles (Portrush) Company Limited | Households | 2018 |
| PEG and Black Ltd | Hospitality | 2024 |
| Pekam Holdings Ltd | Construction | 2022 |
| Perfections Day Spa (NI) Ltd | Wholesale & retail | 2009 |
| Pete Stewart Creative Limited | Professional & scientific | 2025 |
| Peter Diamond Ltd | Real estate | 2014 |
| Peter Mcclarey Electrics Limited | Construction | 2014 |
| Philip Tweedie Ltd | Real estate | 2015 |
| Phillipson Performance Partners Limited | Professional & scientific | 2022 |
| PIC Restaurants Ltd | Hospitality | 2009 |
| Pickle 25 Limited | Information & communication | 2025 |
| Pillar Talent Group Ltd | Administrative & support | 2025 |
| Pine Crest Dentistry Limited | Health & social care | 2026 |
| Piney Way Management Company Limited | Real estate | 2015 |
| Pippa Bridal Ltd | Wholesale & retail | 2019 |
| Place Solutions LLP | | 2021 |
| Playhouse Activity Centre | Education | 2015 |
| Playsheet Ltd | Information & communication | 2024 |
| Plbs Duddy Limited | Financial services | 2019 |
| PM Lynwood Limited | Construction | 2014 |
| PMC Rentals & Management Limited | Real estate | 2013 |
| PMF Plumbing & Heating Services Ltd | Construction | 2016 |
| Pmka Limited | Other services | 2016 |
| Pollock Car Sales Ltd | Wholesale & retail | 2018 |
| Port Constructions Limited | Construction | 2015 |
| Port Vapes Ltd | Wholesale & retail | 2020 |
| Portico Church Limited | Other services | 2024 |
| Portillas Café Limited | Manufacturing | 1985 |
| Portinode Properties Limited | Other services | 2023 |
| Portmagic Limited | Real estate | 2017 |
| Portnahapple Ltd | Other services | 2021 |
| Portnahaven Management Company Ltd | Households | 2017 |
| Portrush by the Sea Ltd | Real estate | 2021 |
| Portstewart Strandview Management Limited | Extraterritorial | 2016 |
| Potting Shed Ventures Limited | Agriculture & fishing | 2024 |
| Poundy Ltd | Wholesale & retail | 2024 |
| Powered Evni Ltd | Construction | 2021 |
| Powerhouse Capital Limited | Professional & scientific | 2009 |
| Powerhouse Estates Limited | Professional & scientific | 2008 |
| Prescient Data Centres Limited | Information & communication | 2016 |
| Prime Place Property Ltd | Real estate | 2020 |
| Professional Turkish Barber Ltd | Other services | 2024 |
| Prolec Building Services Ltd | Construction | 2007 |
| Prometheus Project Limited | Information & communication | 2024 |
| Propiteer Hotels Exeter Limited | Hospitality | 2016 |
| Propiteer North Sound Limited | Real estate | 2016 |
| Prospect Mews Portstewart Management Company Limited | Households | 2003 |
| Prospect Property N.I. Ltd | Real estate | 2022 |
| Prospekt Limited | Professional & scientific | 2025 |
| Psim Ltd | Manufacturing | 2022 |
| PSQ PI Limited | Real estate | 2009 |
| PTB Engineering (NI) Ltd | Professional & scientific | 2023 |
| Pure Deals UK Limited | Wholesale & retail | 2020 |
| Pure Dental Hygiene NI Ltd | Health & social care | 2020 |
| Purple DOT (N. Ireland) Limited | Real estate | 2011 |
| Q4 Estates Ltd | Real estate | 2019 |
| Q44 Limited | Construction | 2019 |
| Qelectrix Ltd | Construction | 2022 |
| Quantec (Coleraine) Ltd | Professional & scientific | 2019 |
| Quarry Heights Management Limited | Households | 2002 |
| Quarry Hill Management (NI) Limited | Households | 2008 |