| AI Diagnostic Systems Ltd | Information & communication | 2026 |
| Aiya Card Limited | Information & communication | 2024 |
| AJ Building Contractors Anglesey Ltd | Construction | 2023 |
| AJ Clinical Services Limited | Other services | 2025 |
| Ajam Group Ltd | Wholesale & retail | 2020 |
| AL Forno Bangor Ltd | Hospitality | 2024 |
| Al-Baraka Foods Ltd | Wholesale & retail | 2017 |
| ALA World Space Limited Limited | Administrative & support | 2025 |
| Alan Corbett Agencies Ltd | Wholesale & retail | 2024 |
| Alan Murphy Consulting Ltd | Construction | 2014 |
| Alchemy Design & Training Ltd | Professional & scientific | 2015 |
| Alexandra Gardens (Sydney Road) Management Company Limited | Households | 2023 |
| Alexandra House (Bangor) Limited | Households | 2010 |
| Alfaretail Ltd | Wholesale & retail | 2026 |
| Algorhythmic Technology Limited | Manufacturing | 1994 |
| Aliznsu Zhang Limited | Wholesale & retail | 2025 |
| ALL Hands on Treats Ltd | Manufacturing | 2024 |
| ALL Round Improvements Ltd | Construction | 2022 |
| ALL Star Bounce N.I Ltd | Administrative & support | 2023 |
| ALL Star Houses Ltd | Real estate | 2023 |
| ALL Wales Auction / Ocsiwn Eiddo Cymru Limited | Extraterritorial | 2009 |
| Allan Harryman Engineering Ltd | Construction | 2003 |
| Allpress Systems Limited | Energy | 2015 |
| Alnajahfialhaya Ltd | Health & social care | 2026 |
| Alpha Gate Holdings Ltd | Real estate | 2018 |
| Alrent Limited | Real estate | 2013 |
| ALS (Dental Surgeon) Limited | Health & social care | 2014 |
| Alsold Limited | Real estate | 2013 |
| ALT Animation Ltd | Information & communication | 2016 |
| Altered Space Limited | Real estate | 2015 |
| Alto Brand Scaling Ltd | Professional & scientific | 2025 |
| Altogether Ltd | Information & communication | 2021 |
| Altro (TAI) Homes Ltd | Real estate | 2025 |
| AM Consulting (NI) Ltd | Professional & scientific | 2014 |
| AM Windows Direct Ltd | Construction | 2010 |
| Amac Property Group Ltd | Households | 2023 |
| AMC Environmental Ltd | Professional & scientific | 2007 |
| AMC Power Management Services Limited | Professional & scientific | 2011 |
| Amgen Services Limited | Professional & scientific | 2017 |
| Amin Pharma Ltd | Professional & scientific | 2022 |
| Ammon Limited | Professional & scientific | 2026 |
| AMP Architecture Ltd | Professional & scientific | 2021 |
| Amtae Limited | Construction | 1999 |
| AN Motors Ltd | Wholesale & retail | 2025 |
| Anderson Wharf (Student) Limited | Construction | 2007 |
| Andrew Hughes Wealth Management CYF | Financial services | 2012 |
| Andy Hanvey Ltd | Professional & scientific | 2023 |
| Angel Holdings (N.I.) Limited | Financial services | 2018 |
| Angladdau Enfys Funerals Ltd | Other services | 2020 |
| Anglesey Adventure Golf Ltd | Arts & recreation | 2023 |
| Anglesey Leisure (UK) Ltd | Hospitality | 2015 |
| Anglesey Lodge Sales Ltd | Real estate | 2016 |
| Anglesey Pilates Studio Ltd | Other services | 2024 |
| Anglesey Roofing Company Limited | Construction | 2005 |
| Anglesey Vintage Equipment Society | Other services | 2014 |
| Anglo Irish Friendships Limited | Professional & scientific | 2023 |
| Anglo Tax and Legal CYF. | Professional & scientific | 2018 |
| Anheddau CYF | Health & social care | 1989 |
| Annaville Limited | Real estate | 2023 |
| Annescourt Developments Limited | Extraterritorial | 1982 |
| Anolad Ltd | Information & communication | 2026 |
| Ansa Reality Ltd | Real estate | 2023 |
| Antur Dyffryn Ogwen CYF. | Health & social care | 1986 |
| Anya Environmental Limited | Professional & scientific | 2015 |
| AP Sports Limited | Wholesale & retail | 2018 |
| Apache One LLP | | 2006 |
| Apcr Limited | Construction | 2018 |
| APD Architects Limited | Professional & scientific | 2021 |
| Apex Advanced Systems Ltd | Information & communication | 2025 |
| Apex Gaming Ltd | Wholesale & retail | 2025 |
| APG Traders Ltd | Wholesale & retail | 2026 |
| Api-Wear Ltd | Wholesale & retail | 2022 |
| Apostolic Faith Mission NI. Shalom Tabernacle CIC | Other services | 2024 |
| Apparel Solutions Ltd | Wholesale & retail | 2018 |
| Appg NI Economy Ltd | Professional & scientific | 2022 |
| Appian-Wilson Limited | Extraterritorial | 1963 |
| Approved Joinery Ltd | Manufacturing | 2023 |
| Appturo Ltd | Information & communication | 2019 |
| Apricot Aesthetics Limited | Other services | 2021 |
| APRIL04 Limited | Administrative & support | 2013 |
| APS (MG) Limited | Professional & scientific | 2017 |
| Aptura Digital Ltd | Information & communication | 2026 |
| Aqua Fresh Private Ltd | Wholesale & retail | 2025 |
| AR Digital Media Publishing Limited | Information & communication | 2022 |
| Arbutus Property Ltd | Real estate | 2023 |
| ARC Properties Bangor Limited | Real estate | 2019 |
| ARCADY108 International Ltd | Wholesale & retail | 2025 |
| ARCADY108 Ltd | Wholesale & retail | 2019 |
| Archaeoleg Brython Archaeology CYF | Professional & scientific | 2017 |
| Archer Property Rentals Ltd | Real estate | 2024 |
| Archibald Consultancy Ltd | Manufacturing | 2025 |
| Archimetrix Ltd | Professional & scientific | 2024 |
| Architects Knox and Markwell Limited | Professional & scientific | 2011 |
| Ardkeen Projects Limited | Professional & scientific | 2019 |
| Ardmore Management Limited | Extraterritorial | 1991 |
| Ards & North Down Community Sports Travel Ltd | Transport & logistics | 2026 |
| Ards Investment & Trust Company Limited | Financial services | 1960 |
| Arfin NI Limited | Hospitality | 2026 |
| Arfon Limited | Real estate | 2020 |
| Arfon Physiotherapy Limited | Health & social care | 2012 |