| Allen Fleming CA Limited | Professional & scientific | 2019 |
| Allen People Solutions Ltd | Professional & scientific | 2007 |
| Allen Propco Limited | Real estate | 2016 |
| Alliance for Choice Belfast Limited | Public administration | 2022 |
| Allied Dunbar Unit Trusts Public Limited Company | | 1987 |
| Allied Oils Limited | Other services | 1985 |
| Alligra Ltd | Information & communication | 2025 |
| Allmarket Group Holdings Ltd | Financial services | 2022 |
| Allmarket Retail Display Solutions Ltd | Construction | 2022 |
| Allmarket Solutions Ltd | Construction | 2019 |
| Allotment Bistro Limited | Hospitality | 2014 |
| Alloys in Motion Ltd | Wholesale & retail | 2025 |
| Allpetz Ltd | Education | 2025 |
| Allskin Limited | Health & social care | 2020 |
| Allsop Consulting Ltd. | Information & communication | 2013 |
| Allsopp Campbell Rainey LLP | | 2024 |
| Allstate Global Holdings Limited | Financial services | 2014 |
| Allstate Northern Ireland Limited | Information & communication | 1998 |
| Allumeer Limited | Wholesale & retail | 2025 |
| Allurach Limited | Administrative & support | 2011 |
| Allure Aesthetics by Mandy Hill Ltd | Other services | 2019 |
| Allybo Ltd | Wholesale & retail | 2023 |
| Almac NI Properties Limited | Real estate | 2022 |
| Almira Holdings Limited | Professional & scientific | 2009 |
| Almira Investments Limited | | 1985 |
| Almond Village Ltd | Construction | 1984 |
| Almot Limited | Hospitality | 2012 |
| Aloa Holdings Ltd | Real estate | 2023 |
| Alolaths Ltd | Wholesale & retail | 2025 |
| ALP Consult Ltd | Professional & scientific | 2022 |
| Alpha Brands Global Ltd. | Wholesale & retail | 2023 |
| Alpha Court Management Company Limited | Households | 2000 |
| Alpha Electrical Distribution Limited | Wholesale & retail | 2015 |
| Alpha Homes (NI) Limited | Construction | 2014 |
| Alpha Marketing PLC | Wholesale & retail | 1988 |
| Alpha Marketing UK Limited | Wholesale & retail | 2010 |
| Alpha Quarry Products Ltd | Mining & quarrying | 2010 |
| Alpha Self Storage Ltd | Transport & logistics | 2024 |
| Alpha Wolf Agency Ltd | Wholesale & retail | 2026 |
| Alphagraphic Inks Limited | Manufacturing | 1987 |
| Alphas JHL Co. Ltd | Wholesale & retail | 2024 |
| Alphatradr Limited | Financial services | 2026 |
| Alpi Commerce Ltd | Wholesale & retail | 2026 |
| Alriyaad Ltd | Education | 2025 |
| Alro Engineering Services Limited | Professional & scientific | 2025 |
| Alsalam Cultural Centre CIC | Education | 2025 |
| Alstom UK CIF Trustee Limited | Administrative & support | 2014 |
| Alta Homes Ltd | Real estate | 2019 |
| Altairon Limited | Wholesale & retail | 2025 |
| Altamuskin Windfarm Limited | Professional & scientific | 2005 |
| Altan Networks Consulting Services Limited | Information & communication | 2016 |
| Altan Properties NI Limited | Real estate | 2021 |
| Altangadas Ltd | Wholesale & retail | 2025 |
| Altaveedan Energy Limited | Energy | 2015 |
| Altera Trade L.P. | | 2017 |
| Alternate Labs Ltd | Information & communication | 2014 |
| Altgolan Wind Farm Holdings Limited | Financial services | 2022 |
| Altgolan Windfarm Limited | Energy | 2006 |
| Altigarron Power Ltd | Energy | 2012 |
| Altitude Chunming Ltd | Wholesale & retail | 2024 |
| Altius Consultants Ltd | Information & communication | 2014 |
| Alto Health UK Ltd | Information & communication | 2024 |
| Altomics Datamation Limited | Professional & scientific | 2020 |
| Altona Developments Ltd | Real estate | 2019 |
| Altona Management Company Limited | Households | 2001 |
| Altona Place Management Limited | Households | 2007 |
| Altona Surveying Ltd | Professional & scientific | 2026 |
| Alu-Fix (UK) Holdings Limited | Manufacturing | 2013 |
| Alucra Developments Limited | Construction | 2009 |
| Alufab Engineering Ltd | Manufacturing | 2024 |
| Alusru Holdings Ltd | Financial services | 2021 |
| Alutec Engineering Limited | Extraterritorial | 2017 |
| Alutect Ltd | Construction | 2002 |
| Alva | Information & communication | 2026 |
| Always Uncool Ltd | Hospitality | 2021 |
| Alwaysmapit Ltd | Information & communication | 2025 |
| Alyson Hogg Ltd | Other services | 2019 |
| ALZ Belfast Ltd | Real estate | 2012 |
| Al’S Café Ltd | Hospitality | 2021 |
| AM Civil Engineering Services Ltd | Professional & scientific | 2021 |
| AM Consulting Engineers Holdings Ltd | Professional & scientific | 2025 |
| AM Dodds Catering Limited | Hospitality | 2019 |
| AM Events N.I. Ltd | Administrative & support | 2026 |
| AM GMP Limited | Professional & scientific | 2023 |
| AM Golf Ltd | Arts & recreation | 2025 |
| AM Group Properties Ltd | Administrative & support | 2017 |
| AM Online Coaching Ltd | Education | 2024 |
| AM Powerwashing Ltd | Administrative & support | 2016 |
| AM Property Management (NI) Ltd | Real estate | 2006 |
| AM R Electrical Ltd | Construction | 2020 |
| AM Shan Removals Ltd | Transport & logistics | 2021 |
| AM Tiling Ltd | Construction | 2022 |
| AM Trading Ireland Limited | Wholesale & retail | 2019 |
| AM Transport Services Holdings Limited | Financial services | 2021 |
| AM Transport Services Topco Limited | Financial services | 2025 |
| Am/Pm Facility Services Ltd | Administrative & support | 2015 |
| Am:Pm Belfast Limited | Hospitality | 2016 |
| Am:Pm Property Limited | Real estate | 2016 |
| AMA PA Limited | Administrative & support | 2021 |
| Amac Cleaning Services Limited | Administrative & support | 2024 |