| ARD Brid Management Company Ltd | Households | 2018 |
| ARD Green Ltd | Wholesale & retail | 2025 |
| Ardghal Ltd | Health & social care | 2022 |
| Ardrose Limited | Health & social care | 2020 |
| Ardross Construction Limited | Construction | 2026 |
| Ardun Carpentry Limited | Construction | 2018 |
| Ardview Developments Limited | Health & social care | 2009 |
| Areal Trading LP | | 2019 |
| Aremis Consulting Ltd | Professional & scientific | 2019 |
| Aremis Ltd | Professional & scientific | 2002 |
| Arieva EHS Solution Ltd | Professional & scientific | 2025 |
| ARK Fusion Ltd | Wholesale & retail | 2020 |
| Arka Intellect Limited | Information & communication | 2010 |
| Arkk Pure Ltd | Professional & scientific | 2016 |
| Armada Trade LP | | 2022 |
| Armagh BIO Refinery Ltd | Wholesale & retail | 2006 |
| Armagh Food Centre Limited | Wholesale & retail | 2016 |
| Armagh Tavern Newco Ltd | Financial services | 2025 |
| Armaghmourne GAS Company Limited | Administrative & support | 1980 |
| Armgods Ltd | Other services | 2024 |
| Arnco Services Ltd | Administrative & support | 2023 |
| Aroj Ltd | Professional & scientific | 2014 |
| Aroma Scents and Gifts Limited | Wholesale & retail | 2021 |
| Around a Fiver Ltd | Wholesale & retail | 2023 |
| Around a Pound Limited | Wholesale & retail | 2001 |
| Around Noon (Print) Limited | Manufacturing | 2019 |
| Around Noon Limited | Wholesale & retail | 2007 |
| Art Bar Funkel Ltd | Hospitality | 2015 |
| Art of Wealth Consulting Ltd | Other services | 2013 |
| Art on ALL Limited | Financial services | 2026 |
| Art Studio 23 Ltd | Arts & recreation | 2019 |
| Arte Trading Limited | Wholesale & retail | 2026 |
| Arthropharm (NI) Ltd | Wholesale & retail | 2022 |
| Arts Specialist Contracts Limited | Construction | 2018 |
| Asee Holdings Limited | Financial services | 2019 |
| Asgf Logistics Limited | Transport & logistics | 2014 |
| ASH Tiles Limited | Wholesale & retail | 2016 |
| Ashburren Ltd | Construction | 2024 |
| Ashgrove Hall (Newry) Limited | Households | 2001 |
| Ashley Apartments (Newcastle) Limited | Households | 2015 |
| Ashley Hill Armagh Ltd | Households | 2022 |
| Ashley Park Lane Management Company Limited | Households | 2021 |
| Ashroe Limited | Real estate | 2024 |
| Ashton Investments Limited | Financial services | 2025 |
| Ashtree Financial Holdings Ltd | Financial services | 2023 |
| Ashtree Financial Services Ltd | Financial services | 2016 |
| Ashview Farm (N.I) Ltd | Manufacturing | 2021 |
| ASM (N) Ltd | Professional & scientific | 2005 |
| ASM Accountants Limited | Professional & scientific | 2005 |
| Asphalt Repair Solutions Ltd | Construction | 2023 |
| Aspire Safety Resources Ltd | Professional & scientific | 2023 |
| Assertive Safety Solutions Limited | Administrative & support | 2026 |
| Assessio Learning Limited | Information & communication | 2024 |
| Asset Integrated Systems Ltd | Information & communication | 2020 |
| Asset Tracker Ltd | Wholesale & retail | 2020 |
| Associated Farming Groups Ltd | Agriculture & fishing | 2002 |
| Associated Fire Protection (NI) Limited | Public administration | 2013 |
| Assure Moveni Limited | Real estate | 2026 |
| Aston Finch Ltd | Wholesale & retail | 2025 |
| Aston-Crean UK Limited | Construction | 2010 |
| Astralis Solutions Ltd | Information & communication | 2023 |
| Atlantic NDT Limited | Construction | 2016 |
| Atlas Acquisitions Limited | | 2002 |
| Atlas Bricklaying Limited | Construction | 2019 |
| Atlas Financial Planning Limited | Financial services | 2005 |
| ATM Fibreglass Roofing Limited | Construction | 2019 |
| Atom Trade LP | | 2018 |
| ATS ALL Trade Solutions Limited | Professional & scientific | 2023 |
| Aughanduff Contracts Limited | Construction | 2026 |
| Aughnahoory Farms Ltd | Extraterritorial | 2018 |
| Aunt Minnies Farm Ltd | Agriculture & fishing | 2023 |
| Aura Nails Beauty and Head Spa Limited | Other services | 2026 |
| Aura Stone Ltd | Manufacturing | 2012 |
| Aurora Electrical & Construction Services Ltd | Construction | 2022 |
| Aurora NA Mara Management Company Limited | Households | 2006 |
| Austin Matthews Agencies Limited | Wholesale & retail | 2024 |
| Auto 4X4 Spares Ltd | Wholesale & retail | 2025 |
| Auto AOM Ltd | Professional & scientific | 2019 |
| Auto Garage 224 Recovery Services Ltd | Wholesale & retail | 2025 |
| Auto Sales Remap UK Ltd | Wholesale & retail | 2025 |
| Auto Saver (NI) Limited | Wholesale & retail | 2015 |
| Auto Supplies (Newry) Ltd | Wholesale & retail | 2005 |
| Auto Trade and Distribution Ltd | Wholesale & retail | 2022 |
| Auto UK Group Limited | Wholesale & retail | 2024 |
| Automate to Grow Systems Limited | Professional & scientific | 2025 |
| AUTOMATE2CONTROL Ltd | Information & communication | 2015 |
| Autopaint (N. Ireland) Ltd | Wholesale & retail | 2014 |
| AVA Bangor Ltd | Hospitality | 2025 |
| AVA House Management Company Limited | Households | 2004 |
| Averarde Limited | Health & social care | 2021 |
| Avia Project Management Partners Limited | Professional & scientific | 2016 |
| Avitor Distribution UK Limited | Wholesale & retail | 2020 |
| AVM (NI) Ltd | Professional & scientific | 2014 |
| Avoca Close Property Management Co Ltd | Professional & scientific | 2008 |
| Avoca Trading Ltd | Real estate | 2023 |
| Avodah Ltd | Construction | 2017 |
| Avvci Ltd | Real estate | 2023 |
| AWT Logistics & Plant Sales Limited | Wholesale & retail | 2019 |
| AX Board Limited | Manufacturing | 2009 |
| Axonnr Ltd | Information & communication | 2022 |