| ARN Properties Limited | Real estate | 2015 |
| Arnie's Resto Belfast Ltd | Hospitality | 2026 |
| Arnolds Belfast Ltd | Hospitality | 2019 |
| Aroma Hygiene Limited | Water & waste | 2006 |
| Aromathy Ltd | Information & communication | 2026 |
| Aroro Care Limited | Health & social care | 2021 |
| Arox Core Ltd | Wholesale & retail | 2026 |
| Arralis Technologies Ltd. | Professional & scientific | 2013 |
| Arranmore Services Ltd | Administrative & support | 2020 |
| Array Academy Limited | Health & social care | 2018 |
| Arri Rental NI Ltd | Administrative & support | 2024 |
| Arrk Electrical Ltd | Construction | 2026 |
| Arro Contracts Ltd | Construction | 2026 |
| Arro Group Limited | Professional & scientific | 2016 |
| Arroll Holdings Limited | Financial services | 2021 |
| Arron Marks Limited | Wholesale & retail | 2024 |
| Arrow Travel Ltd | Administrative & support | 2023 |
| Arrowhead Homes Limited | Real estate | 2019 |
| ARS & Fortis Limited | Information & communication | 2024 |
| Arslan Masih Ltd | Wholesale & retail | 2025 |
| Art Chloe Ellis Ltd | Arts & recreation | 2022 |
| Art Home&Away Holywood Limited | Wholesale & retail | 2025 |
| Art Loves Ltd | Arts & recreation | 2014 |
| Art on Fashion Ltd. | Wholesale & retail | 2010 |
| Art Visualiser Ltd | Information & communication | 2018 |
| Artana Management Limited | Extraterritorial | 2004 |
| Artbook Cute Limited | Wholesale & retail | 2025 |
| Artemis Applied Technologies (Aatl) Ltd | Information & communication | 2025 |
| Artemis Applied Technologies Ltd | Information & communication | 2023 |
| Artemis Developments Limited | Real estate | 2007 |
| Artemis Search and Selection Limited | Administrative & support | 2022 |
| Artemis Technologies Services Ltd | Transport & logistics | 2024 |
| Artgalore Limited | Wholesale & retail | 2024 |
| Arthouse DK Ltd | Hospitality | 2018 |
| Arthritisni Limited | Health & social care | 2023 |
| Arthur COX (N.I.) LLP | | 2019 |
| Arthur Street Films Limited | Information & communication | 2015 |
| Arthur Street Mews Management Limited | Households | 2008 |
| Arthur Toren Associates Ltd | Professional & scientific | 2019 |
| Arthurs Coffee Co Ltd | Hospitality | 2012 |
| Artificialdev Limited | Information & communication | 2017 |
| Artigrass Limited | Administrative & support | 2017 |
| Artios Insights Ltd | Extraterritorial | 2015 |
| Artisan Oven Ltd | Hospitality | 2020 |
| Artist Guitars Ltd | Wholesale & retail | 2015 |
| Artizan Fabrications Limited | Manufacturing | 2017 |
| Arts & Business Northern Ireland | Administrative & support | 2011 |
| Arts & Business Northern Ireland Services Limited | Extraterritorial | 2011 |
| Arts & Disability Forum | Arts & recreation | 2004 |
| Arts Care Limited | Health & social care | 2006 |
| Arts Ekta | Arts & recreation | 2006 |
| Arts for ALL | Arts & recreation | 2004 |
| ARU Foods Limited | Hospitality | 2021 |
| Aruba ALL Natural Lifestyle Ltd | Wholesale & retail | 2018 |
| Arubty Ltd | Wholesale & retail | 2025 |
| Arura NI Trust | Other services | 2021 |
| Arvatix Global Ltd | Wholesale & retail | 2025 |
| Arvaton Commerce Ltd | Wholesale & retail | 2025 |
| Arven 194 Limited | Real estate | 2024 |
| Arven 64 Limited | Construction | 2019 |
| Arvore Growth Capital Limited | Financial services | 2025 |
| ARX Automotive Limited | Manufacturing | 2025 |
| ARX Digital Ltd | Information & communication | 2025 |
| Arxfin Limited | Professional & scientific | 2022 |
| Arxfin Projects Limited | Financial services | 2023 |
| Arya (Europe), Ltd. | Information & communication | 2024 |
| Aryzta UK Holdings Limited | Professional & scientific | 1966 |
| Arzygul Berdiyeva Limited | Wholesale & retail | 2024 |
| AS Contracts Belfast Ltd | Construction | 2025 |
| AS SHE Dreams Ltd | Wholesale & retail | 2020 |
| AS Systems Limited | Construction | 2024 |
| Asad Sardar Ltd | Wholesale & retail | 2026 |
| Asbestos Training and Management Ireland Ltd | Construction | 2012 |
| ASC Radiology Limited | Health & social care | 2015 |
| ASC Sanitation Ltd | Administrative & support | 2024 |
| Ascend & Prosper Ltd | Households | 2024 |
| Ascend Facilities Management Limited | Administrative & support | 2026 |
| Ascend Systems Ltd | Information & communication | 2025 |
| Ascension Lanying Ltd | Wholesale & retail | 2024 |
| Ascent Fawu Limited | Wholesale & retail | 2024 |
| Asclepios Limited | Health & social care | 2022 |
| Ascot Land & Property Developments Ltd | Construction | 2013 |
| ASD Unique Ltd | Wholesale & retail | 2025 |
| ASF Digital Media Ltd | Information & communication | 2020 |
| Asfsky Tech Company Limited | Wholesale & retail | 2025 |
| Asgard Financial Services Limited | Financial services | 2014 |
| Asgarth Properties Limited | Real estate | 2005 |
| ASH Renewables Limited | Energy | 2012 |
| ASH Renewables NO 3 Limited | Energy | 2014 |
| ASH Renewables NO 4 Limited | Energy | 2014 |
| ASH Renewables NO 5 Limited | Energy | 2014 |
| ASH Renewables NO 6 Limited | Energy | 2014 |
| Ash&Cole Ltd | Hospitality | 2023 |
| Asha Wellness CIC | Real estate | 2025 |
| Ashbrook Home (NI) Limited | Health & social care | 2002 |
| Ashcott Developments Limited | Real estate | 2005 |
| Ashdale Engineering Limited | Wholesale & retail | 1979 |
| Ashdene Wood Management Company Limited | Real estate | 2021 |
| Ashfay Properties (N.I.) Ltd | Extraterritorial | 1997 |
| Ashfield DEJ Holdings Limited | Real estate | 2025 |