| Apadana House Ltd | Real estate | 2026 |
| APC Property Services Limited | Real estate | 2017 |
| Apothiq Clinical Services Ltd | Wholesale & retail | 2026 |
| Approach Training Safely Limited | Administrative & support | 2011 |
| AQS Global Limited | Professional & scientific | 2014 |
| Aquaroc Bathrooms Limited | Wholesale & retail | 2016 |
| Aquila Rope Access Trade Solutions Ltd | Construction | 2018 |
| ARC Power Services Ltd | Professional & scientific | 2017 |
| Arcadia NDT Ltd | Professional & scientific | 2022 |
| Arcadiem Limited | Professional & scientific | 2016 |
| ARCH22 Ltd | Professional & scientific | 2022 |
| Archer Construction (North East) Limited | Construction | 2019 |
| Architectural Surveying and Planning Services Limited | Professional & scientific | 2021 |
| Ardent Media Ltd | Professional & scientific | 2025 |
| Arete Healthcare & Education Consultancy Ltd | Education | 2022 |
| Areto Homes Limited | Extraterritorial | 2020 |
| Argus Europe Limited | Administrative & support | 1998 |
| Argus GH Limited | Financial services | 2023 |
| Arion Equestrian Ltd | Wholesale & retail | 2013 |
| ARK Property Investors Ltd | Real estate | 2020 |
| ARK Royale Property Ltd | Extraterritorial | 2024 |
| ARK Therapies Community Interest Company | Education | 2017 |
| Arlington (Milburngate) Limited | Real estate | 2014 |
| Arlo Chester Enterprise Ltd | Financial services | 2021 |
| Armchair Trading Floor Ltd | Administrative & support | 2017 |
| Armo Safety Ltd | Professional & scientific | 2023 |
| Armstrong Electric Services (NE) Limited | Construction | 2026 |
| Arndale Ltd | Real estate | 2022 |
| Arnison Investments Limited | Real estate | 2024 |
| Arnison Solutions Limited | Professional & scientific | 2024 |
| Art of Play CIC | Health & social care | 2024 |
| Artemis House Ltd | Water & waste | 2026 |
| Artemisa Limited | Hospitality | 2020 |
| Arthur House Investments Limited | Real estate | 2020 |
| Artistic Solutions Ltd | Arts & recreation | 2012 |
| Arton Property and Lettings Limited | Real estate | 2025 |
| Ary's Lounge Barber Shop Ltd | Other services | 2025 |
| AS Document Services Ltd | Administrative & support | 2025 |
| Ascend Commercial Limited | Real estate | 2022 |
| Ascend Operations Limited | Financial services | 2022 |
| Ascend Property Limited | Real estate | 2021 |
| Ascend Property Management Limited | Real estate | 2025 |
| Ascenda Site Services Ltd | Construction | 2024 |
| Asensio Ltd | Professional & scientific | 2021 |
| Ashley House Trimdon Development Ltd | Construction | 2020 |
| Ashman Auto Services Ltd | Wholesale & retail | 2026 |
| Ashton & Race Properties Ltd | Real estate | 2022 |
| Ashton Heating & Plumbing Limited | Construction | 2012 |
| Ashtree UK Limited | Real estate | 2005 |
| Aslim Motors Ltd | Wholesale & retail | 2022 |
| Aspire Bathrooms Limited | Construction | 2015 |
| Aspire Technical Training & Assessment Limited | Education | 2017 |
| Aspra Solutions Limited | Financial services | 2008 |
| Association for Practice Based Approach | Health & social care | 2012 |
| Astar.Engineering Services Ltd | Professional & scientific | 2022 |
| Astontrack Limited | Transport & logistics | 1987 |
| ASW Surveying Limited | Professional & scientific | 2014 |
| AT Ladies Room Ltd | Other services | 2017 |
| AT Mens Room Ltd | Other services | 2017 |
| Atam Digital Solution Ltd | Transport & logistics | 2022 |
| Atec Technical Solutions Limited | Professional & scientific | 2013 |
| Atex (NE) Limited | Construction | 2021 |
| Atex (NW) Limited | Construction | 2021 |
| Atex Electrical Engineering Services Ltd | Administrative & support | 2018 |
| Atex Group Limited | Construction | 2021 |
| Athira Property Limited | Real estate | 2026 |
| ATL Survey Services Limited | Professional & scientific | 2009 |
| Atlantic Tour Operations Limited | Administrative & support | 1996 |
| ATR Rigging Ltd | Manufacturing | 2022 |
| Atriox Engineering Ltd | Professional & scientific | 2026 |
| Attachment Evolution CIC | Health & social care | 2024 |
| Attco Ltd | Transport & logistics | 1999 |
| Atterway Ltd | Other services | 2014 |
| ATTIRE4HIRE Limited | Administrative & support | 2024 |
| Attivo Securities Limited | Construction | 1972 |
| Attlift Ltd | Construction | 2025 |
| Authara Limited | Administrative & support | 2025 |
| Auto World North East Ltd | Wholesale & retail | 2025 |
| Autorefinishers (Hartlepool) Ltd | Wholesale & retail | 2026 |
| Autumn Property Services Ltd | Real estate | 2023 |
| Avalon Damac Ltd | Professional & scientific | 2019 |
| Avalon Global Limited | Construction | 2022 |
| Avathan Limited | Administrative & support | 2007 |
| Avenue Events (North) Ltd | Administrative & support | 2006 |
| AW Access Ltd | Construction | 2021 |
| AW Modern Art Limited | Arts & recreation | 2024 |
| AW Solutions Limited Teesside Ltd | Information & communication | 2015 |
| AWG Enterprises Limited | Construction | 2013 |
| Azalea Wealth Management Ltd | Financial services | 2025 |
| B a M Holdings Hillcarter Ltd | Hospitality | 2025 |
| B a S Properties Limited | Real estate | 2023 |
| B H Inspection Services Ltd | Professional & scientific | 2025 |
| B&W Property Maintenance Limited | Construction | 2025 |
| B1 Hartlepool Boardroom Ltd | Real estate | 2025 |
| B1 Hub Hartlepool Ltd | Real estate | 2025 |
| B1 Office Space Hartlepool Ltd | Real estate | 2025 |
| B2 Tasty Ltd | Hospitality | 2025 |
| BA County Cricket Festivals Ltd | Arts & recreation | 2022 |
| Baanthaihartlepool Ltd | Hospitality | 2026 |
| Babies Blessings Limited | Wholesale & retail | 2009 |