| Alchemy Effects Ltd | Professional & scientific | 2017 |
| Alchemy Tullan Ltd | Financial services | 2021 |
| Alconn Kitchens Limited | Manufacturing | 2004 |
| Aldaar Ltd | Real estate | 2024 |
| Aldens Restaurant Limited | Extraterritorial | 1985 |
| Alderdice (Contracts) Limited | | 1978 |
| Alderock Limited | Extraterritorial | 2012 |
| Alderwood Shoot Ltd | Arts & recreation | 2018 |
| Aldirani Estates Ltd | Real estate | 2026 |
| Alds Trading Limited | Wholesale & retail | 2024 |
| Aleket Global Limited | Wholesale & retail | 2023 |
| Aleksandar's Bakery Limited | Manufacturing | 2019 |
| Alertline Security Ltd | Administrative & support | 2025 |
| Alessco Ltd | Professional & scientific | 2010 |
| Alethion Limited | Wholesale & retail | 2025 |
| Alex Beevis Limited | Education | 2025 |
| Alex Macdonald Loyal Rangers Supporters Club Ltd | Arts & recreation | 2025 |
| Alex Nash Collection Limited | Wholesale & retail | 2023 |
| Alex's Lifestyle Hub Ltd | Wholesale & retail | 2024 |
| Alex. Devon Limited | Wholesale & retail | 1973 |
| Alexander Byrne Sidhu & Partners (Management Services) | Administrative & support | 2025 |
| Alexander CAP 1 Ltd | Hospitality | 2021 |
| Alexander Contracts Ltd | Construction | 2016 |
| Alexander Hall Global Limited | Transport & logistics | 2015 |
| Alexander House Property Limited | Real estate | 2024 |
| Alexander Kitchen and Bathroom Ltd | Wholesale & retail | 2016 |
| Alexander Plumbing and Heating Ltd | Construction | 2016 |
| Alexander Rankin & SON Limited | Construction | 1974 |
| Alexanders 2 Ltd | Hospitality | 2019 |
| Alexanders Partnership Ltd | Real estate | 2025 |
| Alexandra Park Avenue Apartments Limited | Extraterritorial | 2024 |
| Alexandra Park Development One Ltd | Construction | 2018 |
| Alexandra Park Management Company Limited | Households | 2009 |
| Alexandra Terrace Lisburn Road Limited | Households | 2016 |
| Alexis Marketing (N.I.) Limited | Professional & scientific | 2017 |
| Alexon International Limited | | 1992 |
| ALF Haulage Limited | Transport & logistics | 2015 |
| ALF Holdings Limited | Financial services | 2020 |
| Alfcore Inns Ltd | Hospitality | 2025 |
| Alfred Belfast Limited | Real estate | 2025 |
| Alfred Daisy Foundation | Administrative & support | 2024 |
| Alfred Daisy Holdings Limited | Financial services | 2010 |
| Alfred Holdings Limited | Hospitality | 2026 |
| Alfred House Asset Management Limited | Real estate | 2015 |
| Alfred J Hurst Limited | Wholesale & retail | 1936 |
| Alfred Management Company Limited | Households | 1999 |
| Alfred Street Apartment Management Limited | Households | 2001 |
| Alfred Street Properties Limited | Real estate | 1995 |
| Algal Omega 3 Ltd | Manufacturing | 2015 |
| Algernon Keyes Limited | Wholesale & retail | 2022 |
| Algocom Ltd | Professional & scientific | 2024 |
| Alhashmia Services Ltd | Manufacturing | 2024 |
| ALI Bakari Ltd | Wholesale & retail | 2024 |
| ALI Hamza Pro Ltd | Wholesale & retail | 2025 |
| ALI Treats Ltd | Hospitality | 2026 |
| ALI Ultimate Ltd | Wholesale & retail | 2024 |
| ALI Zoom Ltd | Wholesale & retail | 2025 |
| Alia Properties Belfast Ltd | Construction | 2023 |
| Alice Project Services Ltd | Professional & scientific | 2023 |
| Align Movement Studios Ltd | Other services | 2025 |
| Alimentum Hospitality Ltd | Hospitality | 2024 |
| Alison Amanda Baptiste Ltd | Wholesale & retail | 2024 |
| Alison Gardiner (UK) Ltd | Wholesale & retail | 2019 |
| Alison Gray Recruitment Ltd | Administrative & support | 2015 |
| Alison Ward Ltd | Wholesale & retail | 2025 |
| Alist Comco Ltd | Wholesale & retail | 2025 |
| Alist Tutoring Ltd | Education | 2022 |
| Alistair Steele Ltd | Wholesale & retail | 2024 |
| Alivia Jody Limited | Manufacturing | 2024 |
| Aliya Batool Ltd | Wholesale & retail | 2025 |
| Aliz Express & Pizza House Ltd | Hospitality | 2025 |
| ALJ Noiliw Ltd | Wholesale & retail | 2024 |
| Aljoy Unique Ltd | Wholesale & retail | 2024 |
| ALL Cargo UK Ltd | Transport & logistics | 2017 |
| ALL Charge N.I Ltd | Construction | 2024 |
| ALL Electronics Ireland Ltd | Information & communication | 2021 |
| ALL for One AI Ltd | Information & communication | 2024 |
| ALL Good Holdings (2021) Limited | Financial services | 2021 |
| ALL Holdings Belfast Ltd | Financial services | 2025 |
| ALL in Coaching Ltd | Education | 2025 |
| ALL Ireland Music Entertainment and Production Ltd | Information & communication | 2017 |
| ALL My Socials Ltd | Administrative & support | 2021 |
| ALL Nations Ministries | Other services | 2010 |
| ALL One Trading and Investments Ltd | Financial services | 2023 |
| ALL SET UP Ltd | Construction | 2020 |
| ALL SO Perfect Limited | Hospitality | 2023 |
| ALL Sports Fitness Ltd | Arts & recreation | 2026 |
| ALL Sports Gym Ltd | Arts & recreation | 2019 |
| ALL the Way Creative Ltd | Professional & scientific | 2021 |
| ALL Things Genomic Ltd | Other services | 2024 |
| ALL Ventilation Services Ltd | Construction | 2019 |
| Allan Ewing Limited | Manufacturing | 2021 |
| Allanur Nepesov Limited | Wholesale & retail | 2024 |
| Allauto North Ltd | Wholesale & retail | 2021 |
| Allbac Limited | Manufacturing | 2025 |
| Allbest Goshop Limited | Wholesale & retail | 2025 |
| Allegro DVT UK Ltd | Information & communication | 2015 |
| Allegro Investments Limited | Real estate | 2017 |
| Allen & Mellon Environmental Limited | Professional & scientific | 2003 |
| Allen Consulting (Ta+A) Limited | Professional & scientific | 2011 |