| AAJ Convenience Store Ltd | Wholesale & retail | 2019 |
| Aalmina Limited | Wholesale & retail | 2024 |
| Aasru Ltd | Real estate | 2026 |
| Aatk Consultants Ltd | Administrative & support | 2021 |
| AB Groundworks North East Ltd | Construction | 2019 |
| Abbey Garth Limited | Mining & quarrying | 2025 |
| Abbey Hospitality Ltd | Hospitality | 2021 |
| Abbeyfield England Limited | Administrative & support | 2022 |
| Abbeyfield World Council | Administrative & support | 2024 |
| Abbeywood Developments Limited | Real estate | 2020 |
| Abbeywood Interiors Limited | Construction | 2007 |
| Abbotside Construction Ltd | Construction | 2026 |
| Abbotts Heating and Plumbing Ltd | Construction | 2023 |
| ABC North East Limited | Professional & scientific | 2009 |
| ABC Rental Properties Limited | Real estate | 2009 |
| Ability Advocates Limited | Administrative & support | 2023 |
| ABL Resources Ltd | Professional & scientific | 2002 |
| ABL Resources Property Management Ltd | Real estate | 2003 |
| Abruzzo Ltd | Hospitality | 2026 |
| Absolute ARB Care Ltd | Agriculture & fishing | 2024 |
| Absolute Fire and Electrical Services Ltd | Manufacturing | 2020 |
| Absolutely Fabulous Properties Ltd | Real estate | 2026 |
| Abundant Earth (Crafts) CIC | Manufacturing | 2025 |
| Abundant Earth (Durham) Limited | Agriculture & fishing | 2006 |
| Abundant Roots Limited | Arts & recreation | 2010 |
| AC Finance Solutions Ltd | Professional & scientific | 2014 |
| Academy Wear UK Ltd | Wholesale & retail | 2013 |
| Acar Trading Ltd | Wholesale & retail | 2023 |
| Accelerate NE Business Ltd | Professional & scientific | 2020 |
| Accounts by Zodrm Ltd | Professional & scientific | 2021 |
| ACD Groundworks Limited | Construction | 2017 |
| ACD Surfacing Limited | Administrative & support | 2024 |
| Ace Motorcycle Training (Durham) Limited | Wholesale & retail | 2001 |
| Ace Motorcycle Training N/E Limited | Education | 2013 |
| Ace PEP Ltd | Wholesale & retail | 2026 |
| Ace Plumbing & Heating Limited | Construction | 2014 |
| Ace Vintage Limited | Wholesale & retail | 2023 |
| Acfaultpro Ltd | Information & communication | 2026 |
| Achieve Digital Marketing Ltd | Information & communication | 1999 |
| ACL Holdings (NE) Ltd | Financial services | 2019 |
| ACM Portfolios Ltd | Real estate | 2022 |
| ACM Solutions NE Limited | Administrative & support | 2022 |
| Acorn Plumbing & Heating Services Limited | Construction | 2005 |
| Acquire Construction Limited | Construction | 2022 |
| Acquire Recruitment Limited | Administrative & support | 2022 |
| Acquiri Limited | Professional & scientific | 2024 |
| Acrebroad Limited | Construction | 1984 |
| Acroflex Dance Academy Ltd | Arts & recreation | 2023 |
| ACS Community Projects (ACS UK) Ltd | Administrative & support | 2020 |
| Actif RSV Ltd | Administrative & support | 2004 |
| Activate Theatre Ltd | Arts & recreation | 2015 |
| Activate Training Ltd | Professional & scientific | 2018 |
| Active Electrical Services (N.E.) Limited | Construction | 2010 |
| ACTIVE2LEARN CIC | Education | 2020 |
| Acts Unseen Ltd | Wholesale & retail | 2021 |
| AD Carr Ellison House Ltd | Construction | 2025 |
| AD Paving & Landscaping Ltd | Administrative & support | 2019 |
| AD Victoriam Limited | Manufacturing | 2018 |
| Adam & Amin Ltd | Wholesale & retail | 2019 |
| Adbac Investments Limited | Financial services | 2022 |
| Additive Manufacturing 3D Technology Ltd | Wholesale & retail | 2017 |
| Addressing Domestic Abuse Community Interest Company | Professional & scientific | 2021 |
| Adelson Limited | Construction | 2004 |
| Adewuyi Holdings Ltd | Financial services | 2026 |
| Adhd Connections Ltd | Public administration | 2025 |
| ADL Homes Limited | Real estate | 2022 |
| ADL Structural Fabrications Ltd | Manufacturing | 2021 |
| Adopter Ltd | Information & communication | 2021 |
| Adore YOU Limited | Manufacturing | 2017 |
| ADP Property (NE) Ltd | Construction | 2014 |
| Advanced Building Solutions NE Ltd | Construction | 2016 |
| Advanced Renovations & Joinery Limited | Construction | 2019 |
| Advanced Roofing NE Ltd | Construction | 2025 |
| Advancing Attachments Ltd | Health & social care | 2019 |
| Advantex Solutions Limited | Information & communication | 2024 |
| Advice Direct South Limited | Information & communication | 2014 |
| AE Data Limited | Information & communication | 2019 |
| AE Sports Coaching Limited | Education | 2021 |
| AEC Wind Ltd | Extraterritorial | 2019 |
| Aegisworks Limited | Professional & scientific | 2020 |
| Aergard Ltd | Extraterritorial | 2026 |
| Aerial Surveys NE Ltd | Professional & scientific | 2025 |
| Aetrio Holdings Limited | Administrative & support | 2015 |
| AF Industrial Ltd | Real estate | 2019 |
| AF Management Consultancy Limited | Financial services | 2020 |
| Affinity Business Limited | Information & communication | 2023 |
| Afiya Wellness Lounge Ltd | Other services | 2025 |
| AFR Holdings (NE) Limited | Financial services | 2026 |
| AFR Properties & Services Ltd | Real estate | 2025 |
| Afraysenes Ltd | Wholesale & retail | 2025 |
| Africcon Limited | Wholesale & retail | 2020 |
| Africom Investments Ltd | Real estate | 2025 |
| Afterglow Shotton Ltd | Other services | 2023 |
| AG & JG Electrical Limited | Construction | 2017 |
| AG & M PUB Company Ltd | Hospitality | 2023 |
| AG Deliverys Ltd | Transport & logistics | 2025 |
| AG Events Limited | Arts & recreation | 2020 |
| AGA Properties NE Ltd | Real estate | 2025 |
| AGE Concern Durham County | Other services | 2007 |
| AGE Concern Durham County Trading Limited | Other services | 1996 |