| 07640248 Limited | Administrative & support | 2011 |
| 106 Woodcraft Ltd | Manufacturing | 2026 |
| 11ARCHES | Arts & recreation | 2014 |
| 11ARCHES Construction Limited | Construction | 2025 |
| 11ARCHES Night Show Limited | Arts & recreation | 2014 |
| 123HELP4FAMILYS CIC | Other services | 2022 |
| 1873 RTM Company Limited | Households | 2022 |
| 22 Auckland Property Ltd | Real estate | 2025 |
| 23 (UK) Limited | Real estate | 2014 |
| 247 Rescue Limited | Extraterritorial | 2017 |
| 252 Decorating Ltd | Construction | 2026 |
| 3 Saints Property Limited | Real estate | 2023 |
| 360 Automation PTY UK Limited | Wholesale & retail | 2024 |
| 3DNEST Limited | Real estate | 2025 |
| 4D Joinery (North East) Limited | Construction | 2017 |
| 4TRACK Care Ltd | Education | 2023 |
| 6MEDIA NE Ltd | Information & communication | 2017 |
| A & H Site Line Boring & Machining Ltd | Manufacturing | 2015 |
| A & M Bathrooms Limited | Construction | 2009 |
| A & P Mechanical Ltd | Construction | 2025 |
| A & S Training Limited | Administrative & support | 2024 |
| A Blacklock Floor Screeding Ltd | Construction | 2025 |
| A Dennis Contracting Limited | Construction | 2021 |
| A G Building Solutions Ltd | Construction | 2023 |
| A Thomson Engineering Ltd | Professional & scientific | 2013 |
| A Toward Properties Limited | Real estate | 2005 |
| A&C Motorcycle Training Ltd | Education | 2021 |
| A&L Marriott Ltd | Wholesale & retail | 2016 |
| A-Byte Computer Solutions Limited | Information & communication | 2011 |
| A.E.T. Ltd | Administrative & support | 1997 |
| A.M.G. Business & Commercial Finance Consultants Limited | Professional & scientific | 2020 |
| A.R. Mcconnell Limited | Wholesale & retail | 2004 |
| AA Electrical & Security Systems Limited | Construction | 2024 |
| Aabat Limited | Transport & logistics | 1998 |
| AAH Climate Limited | Transport & logistics | 2019 |
| AAH Digital Developments Ltd | Professional & scientific | 2022 |
| Aasa Ventures Ltd | Real estate | 2022 |
| Abbey Park (Ampleforth) Management Company Limited | Households | 2014 |
| ABC IT Limited | Information & communication | 2015 |
| ABM Farms Limited | Agriculture & fishing | 2005 |
| Absolute Cleaning Solutions (GBR) Ltd | Administrative & support | 2020 |
| Absolute Plumbing & Heating North East Ltd | Construction | 2021 |
| ABT Plumbing Heating & Renewables Ltd | Construction | 2024 |
| ABU Trans Ltd | Transport & logistics | 2021 |
| AC Building Services (NE) Ltd | Construction | 2026 |
| Ac/Cc Events Limited | Hospitality | 2026 |
| Academy Angels Limited | Arts & recreation | 2020 |
| Accc Properties Limited | Real estate | 2026 |
| Acdc Holdings Ltd | Health & social care | 2022 |
| ACG Construction Northern Ltd | Construction | 2020 |
| ACL (Structural Steel) Limited | Manufacturing | 2013 |
| Aclet Property Management & Services Limited | Real estate | 1999 |
| Acorn HOG Roast Limited | Hospitality | 2019 |
| Acrum Leisure Ltd | Hospitality | 2023 |
| Activate Safeguarding Resolutions Ltd | Professional & scientific | 2018 |
| Active Future Darlington CIC | Arts & recreation | 2025 |
| Actuate Mortgages Ltd | Financial services | 2025 |
| AD Utilities Ltd | Construction | 2021 |
| Adamnewby Limited | Construction | 2020 |
| Admire Fitness Ltd | Arts & recreation | 2024 |
| Adra Projects Ltd | Professional & scientific | 2023 |
| Adty Limited | Manufacturing | 2025 |
| Advanced Paving and Landscaping NE Ltd | Administrative & support | 2026 |
| Advanced Plumbing Solutions (North East) Limited | Construction | 2009 |
| Advanced Radiation Protection Ltd | Professional & scientific | 2025 |
| Aether and Oak Ltd | Education | 2025 |
| Afeuk Ltd | Financial services | 2016 |
| African Dreams Ltd | Administrative & support | 2018 |
| Afrohair Empire Limited | Other services | 2025 |
| AFS Motor Trade Limited | Wholesale & retail | 2026 |
| AG Electrical Solutions Ltd | Manufacturing | 2020 |
| AG Electrical Solutions NE Ltd | Construction | 2026 |
| AG Spray Solutions Ltd | Construction | 2023 |
| Agrijet Limited | Manufacturing | 2025 |
| AH Race Support Limited | Wholesale & retail | 2020 |
| AHB Cladding Ltd | Construction | 2021 |
| AI Plumbing & Heating Limited | Construction | 2011 |
| Aiwc Commercial and Business Cleaning Limited | Administrative & support | 2024 |
| Ajax Design Ltd | Professional & scientific | 2014 |
| AJW Holdings Group Ltd | Financial services | 2025 |
| AK Boxing Coaching Limited | Arts & recreation | 2020 |
| AK Hussain Ltd | Wholesale & retail | 2019 |
| AK North East Property Specialist Limited | Real estate | 2021 |
| AKA Building Resources Ltd | Construction | 2025 |
| Akshaya Food and Wine Ltd | Wholesale & retail | 2014 |
| Alan Rosemurgey Drystone Walling Ltd | Construction | 2025 |
| Alan Sewell Limited | Wholesale & retail | 2001 |
| Alex Green Limited | Real estate | 2023 |
| ALG Motors Limited | Wholesale & retail | 2016 |
| ALJ Capital Holdings Ltd | Financial services | 2026 |
| ALL Clear Pest Control (Bishop Auckland) Ltd | Administrative & support | 2016 |
| ALL OUT Strength and Conditioning Limited | Arts & recreation | 2014 |
| Allabouttrees Limited | Agriculture & fishing | 2004 |
| Allen Sykes Audit Limited | Professional & scientific | 2025 |
| Allen Sykes Limited | Professional & scientific | 1988 |
| Allerton Property Management Ltd. | Real estate | 2015 |
| Alliance Occupational Health Ltd | Health & social care | 2025 |
| Allstarr Limited | Health & social care | 2017 |
| Alpha Physio Services Ltd | Health & social care | 2019 |
| Alternative Energy Contracting Ltd | Construction | 2006 |