| Agape Communications Ltd | Manufacturing | 2008 |
| Agar - Professional Cleaning Ltd | Administrative & support | 2020 |
| Agatha Bagatha Limited | Other services | 2013 |
| Agbaje Medical Limited | Health & social care | 2013 |
| Agbaje Property Limited | Real estate | 2020 |
| AGC Steel Limited | Manufacturing | 2025 |
| AGE NI | Health & social care | 2009 |
| AGE NI Enterprises Limited | Extraterritorial | 2014 |
| AGE Well Aesthetics Ltd | Other services | 2023 |
| Agency Hair Ltd | Other services | 2026 |
| Agent 65 Ltd | Information & communication | 2025 |
| Agent Transform Limited | Information & communication | 2025 |
| Aghafad Limited | Professional & scientific | 2016 |
| Aghalee Design Services Ltd | Construction | 2025 |
| Aghalee Gift Shop Ltd | Wholesale & retail | 2019 |
| Agile Growth Systems Limited | Professional & scientific | 2019 |
| Agile Mindset Mastery Ltd | Professional & scientific | 2025 |
| Agio AI UK Limited | Information & communication | 2020 |
| AGK Engineer Consulting Limited | Professional & scientific | 2026 |
| Agnew Andress Higgins Solicitors Limited | Professional & scientific | 2012 |
| Agnew Commercials Limited | Wholesale & retail | 1978 |
| Agnew Group Holdings Ltd | Professional & scientific | 2026 |
| Agnew Leasing Ltd | Wholesale & retail | 1977 |
| Agnew Propco Limited | Real estate | 2011 |
| Agnew Recovery Services Limited | Administrative & support | 2010 |
| Agnew Retail Limited | Professional & scientific | 2012 |
| Agnew TEN Limited | Financial services | 2020 |
| Agnieszka & Robert Gilmour Architects Ltd | Professional & scientific | 2010 |
| Agnosto Ltd | Wholesale & retail | 2025 |
| Agora Branding Consultancy Ltd | Professional & scientific | 2025 |
| AGR Imports Limited | Energy | 2022 |
| Agr(Ni) Limited | Agriculture & fishing | 2019 |
| Agra BD Ltd | Hospitality | 2026 |
| Agrenergy Limited | Construction | 2026 |
| Agri-Trans Ltd | Administrative & support | 2014 |
| Agricolas Investments Ltd | Real estate | 2015 |
| Agridata Ireland Limited | Information & communication | 2014 |
| Agro Security Services Limited | Public administration | 2022 |
| Agro Torg LP | | 2018 |
| AGS Partners Limited | Administrative & support | 2012 |
| AGV (Annesborough) Limited | Energy | 2018 |
| AGV (Craigavon) Limited | Energy | 2017 |
| AGV Dufless Limited | Energy | 2023 |
| AGV Energy Limited | Energy | 2023 |
| AGW Hairdressing Ltd | Other services | 2018 |
| AGW Property Management Ltd | Households | 2022 |
| AH CRN Holdco Limited | Financial services | 2024 |
| AH! Spa Ltd | Health & social care | 2025 |
| Ahealtey Ltd | Wholesale & retail | 2025 |
| AHG Limited | Financial services | 2015 |
| AHG Topco Limited | Financial services | 2026 |
| AHM Distribution Ltd | Wholesale & retail | 2022 |
| AHM Foods Ltd | Hospitality | 2026 |
| Ahmed Goods Ltd | Wholesale & retail | 2025 |
| Ahoy Belfast Cruises Ltd | Administrative & support | 2022 |
| Ahsan a Pro Ltd | Wholesale & retail | 2024 |
| Ahvara Solutions Ltd | Information & communication | 2024 |
| AI Data Consulting Limited | Information & communication | 2025 |
| AIA Belfast Ltd | Hospitality | 2024 |
| AIB Group (UK) P.L.C. | Financial services | 1985 |
| AIB Holdings (N.I.) Limited | Financial services | 1989 |
| AIB Unit Trust Managers Limited | | 1986 |
| Aicon Ltd | Wholesale & retail | 2025 |
| AID to the Church in Need Ireland | Other services | 2006 |
| Aida Camp Film Limited | Information & communication | 2025 |
| Aida Property Investments Limited | Real estate | 2014 |
| Aidan Monaghan Photographer Ltd. | Other services | 2019 |
| Aiden Mckenna Limited | Manufacturing | 2019 |
| Aiforya Ltd | Information & communication | 2026 |
| Aifunib Ltd | Wholesale & retail | 2025 |
| AIG Autos Limited | Wholesale & retail | 2011 |
| Aijaz Mart Ltd | Wholesale & retail | 2024 |
| Aiken Communications Limited | Professional & scientific | 2006 |
| Aiken Flux Ltd | Other services | 2025 |
| Aila's Nails & Spa Limited | Other services | 2022 |
| Ailesbury Services Limited | Administrative & support | 2013 |
| Ailing Mint Ltd | Professional & scientific | 2023 |
| Ailsby Language Services Ltd | Professional & scientific | 2018 |
| Ailsebio Limited | Professional & scientific | 2021 |
| Aimi Electronic Technology Limited | Wholesale & retail | 2025 |
| Aimro Limited | Wholesale & retail | 2003 |
| Aindriu Limited | Real estate | 2016 |
| Aine Glackin Architecture & Interiors Limited | Professional & scientific | 2022 |
| Ainesorcha Limited | Professional & scientific | 2019 |
| Aipha Ltd | Information & communication | 2025 |
| Air Core Asset Management Limited | Real estate | 2026 |
| Air Core E Bikes Limited | Administrative & support | 2025 |
| Air Core EV Ltd | Energy | 2020 |
| Air Core Limited | Energy | 2010 |
| Air Core Ventures Limited | Real estate | 2014 |
| Air Corre Ltd | Energy | 2020 |
| Air Energy (NI) Ltd | Professional & scientific | 2007 |
| Air Land Sea Safety Solutions Ltd | Professional & scientific | 2021 |
| Airam Consulting Limited | Professional & scientific | 2026 |
| Airavat Travel Ltd | Transport & logistics | 2026 |
| Airbus Belfast Limited | Manufacturing | 2025 |
| Airception Limited | Professional & scientific | 2009 |
| Aircon Group International Limited | Construction | 2021 |
| Airfolio Limited | Information & communication | 2021 |
| Airglen Limited | Real estate | 1988 |