| Alliance Mechanical Limited | Construction | 2025 |
| Allied Property Solutions Ltd | Real estate | 2014 |
| Allmark (NI) Limited | Manufacturing | 2003 |
| Almd Ltd | Professional & scientific | 2023 |
| Almg | Arts & recreation | 2024 |
| Almotech UK Limited | Manufacturing | 2022 |
| Alpha Caravans Ltd | Wholesale & retail | 2025 |
| Alpha Fitouts Ltd | Construction | 2019 |
| Alpha Trade Bay Ltd | Wholesale & retail | 2022 |
| Alphaclad (NI) Ltd | Construction | 2012 |
| Altera Inter L.P. | | 2015 |
| Alteravox Ltd | Information & communication | 2009 |
| Alternative Experiences UK Limited | Arts & recreation | 2025 |
| Altex Networks L.P. | | 2017 |
| Altnaveigh Properties (N.I.) Limited | Real estate | 1976 |
| Altravana Ltd | Wholesale & retail | 2022 |
| Altum Precision E&I Ltd | Extraterritorial | 2019 |
| Alula Communications Ltd | Information & communication | 2025 |
| Alvitex LP | | 2016 |
| AM Global Distribution Ltd | Wholesale & retail | 2024 |
| Amac Building Ltd | Construction | 2016 |
| Amac Services Ltd | Construction | 2017 |
| Ambassador Communications NI Ltd | Wholesale & retail | 2024 |
| Ambergate Agencies Ltd | Real estate | 1998 |
| AMC (N.I.) Ltd | Wholesale & retail | 2025 |
| AMC Construction (NI) Ltd | Construction | 2014 |
| AMC Construction Group Ltd | Construction | 2021 |
| AMC Construction Holdings Ltd | Real estate | 2021 |
| AMC Mechanical Ltd | Wholesale & retail | 2025 |
| Amcg Financial Limited | Financial services | 2022 |
| Amcn Group Ltd | Construction | 2018 |
| Amcrest Global Holdings Limited | Wholesale & retail | 2023 |
| AMD Consulting Services Ltd | Information & communication | 2025 |
| AMG Fuels Limited | Wholesale & retail | 2018 |
| Amour Beauty (Newry) Ltd | Other services | 2019 |
| Ampm Consultancy Ltd | Professional & scientific | 2021 |
| Ampt Body Transformation Meals Ltd | Manufacturing | 2018 |
| AN Buthal Community Interest Company | Manufacturing | 2023 |
| AN Tobar C.I.C. | Education | 2018 |
| Anachem Limited | Wholesale & retail | 2021 |
| Ancaster Plant Ltd | Manufacturing | 2024 |
| Anchor Engineering Limited | Wholesale & retail | 2018 |
| Ancorra Environmental Limited | Water & waste | 2025 |
| AND Property Ltd | Real estate | 2017 |
| Anderson Site Clearance Limited | Construction | 2024 |
| Andersonstown Services Ltd | Wholesale & retail | 2020 |
| Andonov Pro Ltd | Professional & scientific | 2018 |
| Angmar Sales Ltd | Wholesale & retail | 2024 |
| ANI1 Ltd | Wholesale & retail | 2017 |
| Anjo Wines Limited | Wholesale & retail | 1983 |
| Anley Maritime Agencies Limited | Administrative & support | 1977 |
| Annalong Community Development Association Limited | Other services | 1994 |
| Annbarr Limited | Administrative & support | 2013 |
| Annduff Construction Limited | Construction | 2016 |
| Annett & Ingram Construction Ltd | Construction | 2007 |
| Annett Commercials Ltd | Wholesale & retail | 2025 |
| Annett Contracts Ltd | Construction | 2013 |
| Annett Engineering Ltd | Manufacturing | 2006 |
| Annett Landscaping Ltd | Administrative & support | 2002 |
| Annett Sand & Gravel Ltd | Mining & quarrying | 2003 |
| Annetts Catering Ltd | Hospitality | 2022 |
| Annetts Pet & Play Ltd | Education | 2022 |
| Anovix Ltd | Wholesale & retail | 2024 |
| Anthony Murchan Cars Ltd | Wholesale & retail | 2025 |
| Antrim Road Deli Ltd | Hospitality | 2019 |
| Antuar Limited | Information & communication | 2018 |
| Anvil House Management Co Ltd | Households | 2007 |
| AOB Construction Ltd | Construction | 2022 |
| Aocc Sales & Repairs Ltd | Wholesale & retail | 2025 |
| AON Engineering Limited | Manufacturing | 2025 |
| Aonb Wholesale Ltd | Wholesale & retail | 2024 |
| Aorta Properties Ltd | Wholesale & retail | 2024 |
| AOS Contracts Ltd | Construction | 2016 |
| AP Kelly Contracts (NI) Ltd. | Manufacturing | 2013 |
| Apex Bytes Ltd | Information & communication | 2023 |
| Apex Civils Limited | Construction | 2025 |
| Apex Construction (IRL) Ltd | Construction | 2024 |
| Apex Media and Print Ltd | Administrative & support | 2014 |
| Apex Structures (N.I.) LLP | | 2014 |
| Apiphany Ltd | Wholesale & retail | 2024 |
| Apon (N,I,) Limited | Real estate | 2023 |
| Apple Cabins Ltd | Wholesale & retail | 2025 |
| Apple Lodge Properties Ltd | Households | 2017 |
| Appleton Lodge Management Limited | Households | 2012 |
| Appletree Dental Limited | Health & social care | 2024 |
| Apricot Environmental (NI) Limited | Extraterritorial | 2003 |
| Apricot Environmental Limited | Wholesale & retail | 1999 |
| Aquability Ireland CIC | Health & social care | 2026 |
| AR Electrical Installation Ltd | Construction | 2024 |
| AR Marquees Ltd | Administrative & support | 2025 |
| Arabtec Capital Unlimited | Real estate | 2014 |
| Aragotti Ltd | Wholesale & retail | 2024 |
| Arbitragecs Limited | Wholesale & retail | 2024 |
| Arcadian I.T Ltd. | Information & communication | 2019 |
| Arcadian SA Ltd | Information & communication | 2022 |
| Arcane Crab Limited | Agriculture & fishing | 2022 |
| Archethought Ltd | Information & communication | 2025 |
| Archtec (NI) Ltd | Manufacturing | 2005 |
| Archview Scaffold Solutions Ltd | Construction | 2011 |
| Archville Limited | Agriculture & fishing | 1989 |