| Alskea (Dundonald) Ltd | Construction | 2025 |
| Alskea (Good Shepherd) Ltd | Construction | 2025 |
| Alskea (Hillsborough) Ltd | Construction | 2023 |
| Alskea Holdings Ltd | Financial services | 2025 |
| Altmore Dental Ltd | Health & social care | 2023 |
| Altmore Farms Limited | Agriculture & fishing | 2021 |
| Altmore Holdings Limited | Professional & scientific | 2021 |
| Altmore Physiotherapy Ltd | Health & social care | 2006 |
| Altmore Renewables Limited | Agriculture & fishing | 2014 |
| Altnagar Limited | Transport & logistics | 2026 |
| Altona Properties Limited | Real estate | 2013 |
| ALW Investments Ltd | Financial services | 2022 |
| AM & MB Enterprises Ltd | Hospitality | 2023 |
| AM Electrical Services (NI) Ltd | Construction | 2012 |
| Amberfit Empire Ltd | Wholesale & retail | 2025 |
| Amberfit Workplace Ltd | Health & social care | 2026 |
| AMC365 Ltd | Construction | 2025 |
| AMG Dental Ltd | Health & social care | 2026 |
| AMG Hseq Consultancy Services Ltd | Professional & scientific | 2017 |
| Ampm Flow and Energy Services Limited | Construction | 2013 |
| Amsbc Holdings Ltd | Financial services | 2021 |
| Amsotech Ltd | Wholesale & retail | 2025 |
| AMT Truck Centre Ltd | Wholesale & retail | 2018 |
| Anaconda Global Holdings Ltd | Manufacturing | 2012 |
| Anahoe Ltd | Real estate | 2024 |
| Anala Developments Ltd | Construction | 2003 |
| Anand ALL the Doggy Daycare Ltd | Other services | 2024 |
| Andrew Marks Ltd | Wholesale & retail | 2025 |
| Andrews Poultry Limited | Agriculture & fishing | 2015 |
| Andrews Property Holdings Limited | Real estate | 2017 |
| Angelov 2022 Ltd | Wholesale & retail | 2022 |
| Animal Health and Welfare NI | Professional & scientific | 2012 |
| Annabel Developments Ltd | Administrative & support | 2009 |
| Annaghbeg Estates Limited | Real estate | 2023 |
| Annaghmore Property Developments Ltd | Construction | 2021 |
| Annahavil Farm Limited | Agriculture & fishing | 2025 |
| Annahavil Holdings Ltd | Financial services | 2017 |
| Anne Douglas Ltd | Professional & scientific | 2013 |
| Anne Transports Ltd | Transport & logistics | 2026 |
| ANNS12 Limited | Financial services | 2018 |
| Annstell Ltd | Construction | 2025 |
| ANY Hills Ltd | Real estate | 2010 |
| Aoire Ltd | Professional & scientific | 2021 |
| AP Life Solutions Ltd | Financial services | 2025 |
| APB Farms Limited | Agriculture & fishing | 2024 |
| APC Estates Limited | Real estate | 2016 |
| APC6 Holdings Ltd | Financial services | 2019 |
| Apcm Holdings Ltd | Real estate | 2022 |
| Apex Auto Sales Ltd | Wholesale & retail | 2023 |
| Apex Component Solutions Ltd | Manufacturing | 2024 |
| Apex Fastening Solutions Ltd | Wholesale & retail | 2006 |
| APL Training Ltd | Education | 2024 |
| Apotheke NI Ltd | Wholesale & retail | 2017 |
| Applejames Limited | Wholesale & retail | 2021 |
| APW Law Limited | Professional & scientific | 2016 |
| AQ Electrics Ltd | Construction | 2013 |
| Aquarius OS Ltd | Education | 2026 |
| AR Sales & Rentals Ltd | Wholesale & retail | 2024 |
| ARB (Bellshill) Limited | Energy | 2020 |
| ARB Biogas Limited | Construction | 2023 |
| ARB Process Engineering Limited | Construction | 2016 |
| Architectural Timber Frames Limited | Manufacturing | 2017 |
| Ardboe Bar's & Property Ltd | Hospitality | 2026 |
| Ardboe Community Projects Ltd | Arts & recreation | 2004 |
| Ardboe Developments Ltd | Construction | 2018 |
| Ardboe Manufacturing Company Limited | Manufacturing | 1967 |
| Ardboe Retail Centre Ltd | Real estate | 2018 |
| Ardeen Carehome Ltd | Health & social care | 2010 |
| Ardina Investments Limited | Real estate | 2000 |
| Ardkeen Developments Ltd | Financial services | 2006 |
| Ardman Limited | Information & communication | 2012 |
| Ardmedia Ltd | Information & communication | 2021 |
| Arepp Ltd | Financial services | 2025 |
| ARK Animal Care Limited | Wholesale & retail | 2021 |
| Arlene Jardine Financial Services Limited | Financial services | 2019 |
| Armagh Clean Team Limited | Administrative & support | 2025 |
| Armagh Fuels Ltd | Wholesale & retail | 2015 |
| Armagh Garages Ltd | Wholesale & retail | 2016 |
| Armagh Hydraulics Limited | | 1988 |
| Armagh Industrial Bearing Supplies Ltd | Manufacturing | 2010 |
| Armagh Plant & Commercial Ltd | Wholesale & retail | 2009 |
| Armstrong Holdco Ltd | Financial services | 2025 |
| Arts Autos Ltd | Wholesale & retail | 2013 |
| ASG Commerce Limited | Wholesale & retail | 2024 |
| Ashfield Farms Ltd | Agriculture & fishing | 2023 |
| Ashgate Capital Ltd | Administrative & support | 2025 |
| Ashlock Door Systems Ltd | Construction | 2002 |
| ASM (ABC) Ltd | Administrative & support | 2013 |
| ASM (D) Ltd | Professional & scientific | 2005 |
| Associate Engineering Systems Limited | Manufacturing | 1991 |
| AT Property Ltd | Extraterritorial | 2012 |
| Atec Enterprises Ltd | Manufacturing | 2021 |
| Atikati Properties Ltd | Real estate | 2025 |
| Atir Properties Limited | Real estate | 2022 |
| Atlantic Plant Hire, Drilling, and Crushing Ltd | Mining & quarrying | 2017 |
| Auction Room Holdings Ltd | Financial services | 2023 |
| Auction Rooms Tyrone Ltd | Hospitality | 2018 |
| Aughamullan Retail Limited | Wholesale & retail | 2026 |
| Aughnagar Contracts Limited | Construction | 2003 |
| Aurora Jewellary International Limited | Wholesale & retail | 2025 |