| Agricultural & Industrial Services 2012 Limited | Agriculture & fishing | 2012 |
| Agriculture Vehicle Sales Limited | Extraterritorial | 1957 |
| Agricwind Limited | Extraterritorial | 2012 |
| Agrihomes Limited | Construction | 2015 |
| AH Lurgan Limited | Hospitality | 2023 |
| AH Manufacturing Ltd | Wholesale & retail | 2024 |
| AH Tractors Moira Ltd | Wholesale & retail | 2017 |
| Aida Marketing Limited | Information & communication | 2022 |
| Airfibre Networks Limited | Information & communication | 2018 |
| Airflow Integrity Services Limited | Administrative & support | 2025 |
| AJ Kebab Limited | Hospitality | 2024 |
| AJD Asset Management Ltd | Professional & scientific | 2025 |
| AK Motorcycles Ltd | Wholesale & retail | 2023 |
| Akim Industries Ltd | Manufacturing | 2014 |
| AL Mustafa Ltd | Wholesale & retail | 2019 |
| Alan Brown & Co (NI) Ltd | Financial services | 2012 |
| Alana Travel Ltd | Administrative & support | 2023 |
| Albatros Fertilizers Limited | | 2002 |
| Albora Limited | Wholesale & retail | 2024 |
| Alfred Briggs (Alwood) Ltd | Manufacturing | 2003 |
| Alice Clare Ltd | Other services | 2019 |
| Alice Nails Portadown Ltd | Other services | 2025 |
| Alimo Reformer Ltd | Health & social care | 2026 |
| ALINA000 Ltd | Hospitality | 2026 |
| ALK (N.I.) Limited | Construction | 2015 |
| ALL Fire Ltd | Extraterritorial | 2014 |
| ALL the Little Things Ltd | Construction | 2017 |
| Allen Logistics (NI) Ltd | Transport & logistics | 2001 |
| Allengrove Professional Services Ltd | Information & communication | 2013 |
| Allengrove Property Services Ltd | Real estate | 2016 |
| Allora Trading Ltd | Wholesale & retail | 2026 |
| Allsport Spectator Facilities Ltd | Construction | 2018 |
| ALLSTOCK4U Ltd | Wholesale & retail | 2024 |
| ALM Developments Ltd | Construction | 2024 |
| ALM Financial Ltd | Financial services | 2023 |
| ALM Validation Ltd | Professional & scientific | 2024 |
| Almac (NO. 1) Limited | Extraterritorial | 2001 |
| Almac (NO.2) Limited | Professional & scientific | 1956 |
| Almac Clinical Services Limited | Professional & scientific | 2001 |
| Almac Clinical Services Trustees Limited | Extraterritorial | 2003 |
| Almac Clinical Technologies Limited | Information & communication | 2006 |
| Almac Diagnostic Services Limited | Professional & scientific | 2002 |
| Almac Diagnostics (2004) Limited | Extraterritorial | 2004 |
| Almac Discovery Limited | Professional & scientific | 2003 |
| Almac Founder Share Company Limited | Professional & scientific | 2008 |
| Almac Group (UK) Limited | Other services | 2006 |
| Almac Group Limited | Professional & scientific | 2001 |
| Almac Pharma Services Limited | Manufacturing | 2003 |
| Almac Sciences Limited | Professional & scientific | 2001 |
| Almac Trustees Limited | Extraterritorial | 2001 |
| Almat NI. Ltd | Manufacturing | 2022 |
| Aloe Consulting Ltd | Professional & scientific | 2020 |
| Alpha Brook Property Ltd | Real estate | 2025 |
| Alphabella Ltd | Wholesale & retail | 2018 |
| Alphamed Europe Limited | Extraterritorial | 2005 |
| Alyke Crystals Limited | Real estate | 2026 |
| Alykemmuo & Co Properties Ltd | Real estate | 2025 |
| Amalfi Solutions Limited | Hospitality | 2026 |
| Ambassadors Football (Ireland) | Arts & recreation | 2008 |
| AMC Imports Ltd | Wholesale & retail | 2017 |
| Amca Management Company Limited | Real estate | 2016 |
| Amca Structures Ltd | Professional & scientific | 2012 |
| AMD Residential Ltd | Real estate | 2026 |
| Amdni Catering Ltd | Hospitality | 2025 |
| Amega Tech Ltd | Manufacturing | 2025 |
| Americold Lurgan Transport Ltd | Transport & logistics | 1991 |
| Americold Lurgan Warehousing Ltd | Transport & logistics | 2012 |
| AMK Body Repairs Ltd | Wholesale & retail | 2026 |
| AMK Hardware Limited | Wholesale & retail | 2009 |
| AMR Retail Limited | Wholesale & retail | 2019 |
| AMW Property Limited | Real estate | 2024 |
| AN Cluain Limited | Professional & scientific | 2022 |
| AN Crannagh Ltd | Construction | 2017 |
| Analytical Service & Repair Ltd | Professional & scientific | 2023 |
| Anantshakti Ltd | Professional & scientific | 2024 |
| Andark Developments Limited | Construction | 2021 |
| Andy's OIL Ltd | Wholesale & retail | 2019 |
| Anerl Limited | Arts & recreation | 2023 |
| Angar Limited | Arts & recreation | 2013 |
| Anime Tattcon NI Ltd | Arts & recreation | 2024 |
| ANN Street Regeneration Limited | Construction | 2017 |
| Ann's Care Homes | Health & social care | 2018 |
| Ann's Care Solutions | Professional & scientific | 2023 |
| Anna Vehicle Scratch Repair Ltd | Wholesale & retail | 2025 |
| Anna-Marie Henderson Ltd | Arts & recreation | 2024 |
| Annaghmore Meadows Management Company Ltd | Households | 2016 |
| Annareagh International Ltd | Transport & logistics | 2023 |
| Annesborough Fuels Limited | Wholesale & retail | 2026 |
| ANNS13 Limited | Real estate | 2018 |
| ANNS9 Limited | Real estate | 2017 |
| Annsborough Tyres Limited | Wholesale & retail | 2025 |
| Antdata Group Limited | Information & communication | 2018 |
| Antrim Road Energy Limited | Energy | 2025 |
| AP Harris Consultants Ltd | Professional & scientific | 2026 |
| Apache Catering Limited | Hospitality | 2018 |
| Apex Blinds Limited | Manufacturing | 1993 |
| Apex Property Agency Ltd | Real estate | 2007 |
| Apex Tax Consultancy Limited | Professional & scientific | 2022 |
| Apmg Properties Ltd | Real estate | 2018 |
| Aptus Planning LLP | | 2012 |