| &Elthorne Courts Ltd | Administrative & support | 2025 |
| 22 Pelham Road Wimbledon Limited | Households | 2014 |
| 3S Northumbria Ltd | Professional & scientific | 2023 |
| A Davison Limited | Hospitality | 2019 |
| A J Railson Ltd | Information & communication | 2009 |
| A Lodge Limited | Hospitality | 2018 |
| A P Garrison Limited | Hospitality | 2024 |
| A R Hume Farming Limited | Agriculture & fishing | 2022 |
| A Space to BE Ltd | Education | 2021 |
| A W Wilson Groundworks Ltd. | Construction | 2013 |
| A&A NE Enterprises Ltd | Financial services | 2026 |
| A.& J.Scott Limited | Manufacturing | 1972 |
| AA Taxis and Private Hire Northumberland Limited | Transport & logistics | 2009 |
| Accounts Sorted (Durham) Limited | Professional & scientific | 2014 |
| ACR Golf Limited | Arts & recreation | 2002 |
| Adam Douglas Legal LLP | | 2013 |
| Adam Dunn Ltd. | Administrative & support | 2012 |
| ADR Landscapes Limited | Administrative & support | 2017 |
| Adventure Northumberland Limited | Other services | 2013 |
| Aesthetics Loft Limited | Other services | 2026 |
| Airborne Art Limited | Professional & scientific | 2015 |
| Airspace Limited | Extraterritorial | 2025 |
| Alacrity Maintenance Solutions Ltd | Professional & scientific | 2023 |
| ALC Marine Services Ltd | Professional & scientific | 2025 |
| Alfie’S Valeting and Detailing Ltd | Administrative & support | 2025 |
| Allcroft Associates Ltd | Professional & scientific | 2024 |
| Alncom Ltd. | Construction | 2005 |
| Alndale Limited | Hospitality | 2020 |
| Alnmouth Arts Festival CIC | Arts & recreation | 2024 |
| Alnmouth Consulting Ltd | Professional & scientific | 2024 |
| Alnmouth Ex-Servicemens Club Ltd | Hospitality | 2020 |
| Alnmouth Leisure Ltd | Hospitality | 2019 |
| Alnmouth Premium Properties Ltd | Construction | 1976 |
| Alnmouth Properties Limited | Households | 1964 |
| Alnmouth Village Golf Club Limited | Arts & recreation | 2015 |
| Alnwick Advanced Skin & Laser Clinic Ltd | Other services | 2022 |
| Alnwick Allstars Limited | Arts & recreation | 2023 |
| Alnwick and District Motor Club Limited | Arts & recreation | 1978 |
| Alnwick Arts & Crafts Centre Ltd | Education | 2017 |
| Alnwick Bars Limited | Hospitality | 2020 |
| Alnwick Castle Golf Community Interest Company | Arts & recreation | 2024 |
| Alnwick City Barbers Ltd | Other services | 2023 |
| Alnwick Community Enterprise Limited | Education | 2025 |
| Alnwick Computerware Ltd. | Information & communication | 2005 |
| Alnwick Construction and Engineering Co.,Limited(The) | Professional & scientific | 1962 |
| Alnwick Cricket Club (1837) Limited | Arts & recreation | 2015 |
| Alnwick Financial Management Limited | Financial services | 2002 |
| Alnwick Flames Ltd | Hospitality | 2026 |
| Alnwick Garden Enterprises Limited | Administrative & support | 2002 |
| Alnwick Offshore and Marine Maintenance Ltd. | Real estate | 2008 |
| Alnwick Pet Warehouse Ltd | Wholesale & retail | 2024 |
| Alnwick Phones Ltd | Wholesale & retail | 2024 |
| Alnwick Playhouse Trading Limited | Arts & recreation | 2024 |
| Alnwick Private Hire Ltd | Transport & logistics | 2025 |
| Alnwick Rooms Limited | Hospitality | 2018 |
| Alnwick Storage Limited | Transport & logistics | 2015 |
| Alnwick Story Fest Community Interest Company | Arts & recreation | 2022 |
| Alnwick Vintage & Antique LLP | | 2017 |
| Alnwick Young People's Association Ltd | Health & social care | 2006 |
| Alnwick Youth Hostel Ltd. | Arts & recreation | 2006 |
| Alpenny Limited | Financial services | 2025 |
| Altora Ltd | Wholesale & retail | 2025 |
| Amalfi Invest Ltd | Real estate | 2024 |
| Amble Autopoint Ltd | Wholesale & retail | 2025 |
| AME International (UK) Limited | Manufacturing | 2023 |
| AMT Business (Northumbria) Limited | Professional & scientific | 2004 |
| Andrew Poplett Enterprises Limited | Professional & scientific | 2010 |
| Anjo Projects Limited | Construction | 1996 |
| AP Ruff Ltd | Construction | 2025 |
| Apatite Marketing Ltd | Professional & scientific | 2026 |
| APS (UK) Limited | Construction | 2011 |
| APS Woodworks (Alnwick) Ltd | Construction | 2022 |
| Aqualution Systems Asset Management Limited | Extraterritorial | 2015 |
| Aqualution Systems Ltd | Manufacturing | 2000 |
| ARC Advanced Training Specialists Ltd | Education | 2009 |
| ARF Solutions Limited | Construction | 2022 |
| Argyle Planning Consultancy Ltd | Construction | 2010 |
| Arkle TM Ltd | Construction | 2024 |
| Armtech Services Ltd | Manufacturing | 2026 |
| Aseptic Solutions Limited | Professional & scientific | 2024 |
| Ashley J. Wynne Carpets Ltd | Wholesale & retail | 2017 |
| Ashley J. Wynne Hawkhill Ltd. | Wholesale & retail | 2020 |
| Asia Inflatables Limited | Wholesale & retail | 2021 |
| Askew Wellbeing Ltd | Health & social care | 2024 |
| Associate Designs Limited | Construction | 2007 |
| AT Traders Private Ltd | Wholesale & retail | 2024 |
| Atlas Lifting & Rigging UK Limited | Manufacturing | 2025 |
| Attraction Films Ltd | Information & communication | 2017 |
| Autostart Limited | Wholesale & retail | 2011 |
| AV8 Subsea Limited | Professional & scientific | 2021 |
| Avalonia Properties Limited | Real estate | 2020 |
| Avie Property Ltd | Real estate | 2025 |
| Aynsley Construction Ltd | Construction | 2024 |
| Aysgarth Classics Limited | Wholesale & retail | 2018 |
| Aysgarth Projects Limited | Real estate | 2013 |
| B. Weightman Ltd. | Construction | 2003 |
| Baboo Aziz Ltd | Hospitality | 2025 |
| Baik Consulting Ltd | Professional & scientific | 2024 |
| Bailiffgate Hotel Limited | Hospitality | 2023 |
| Bari Tea Ltd | Professional & scientific | 2010 |