| 1094 Associates Ltd | Information & communication | 2024 |
| 121 Business Links Limited | Administrative & support | 2024 |
| 1506 Joinery Limited | Construction | 2025 |
| 1992 Joinery Limited | Construction | 2022 |
| 1ST Class Drive Cleaning Limited | Administrative & support | 2025 |
| 24/7 Removals (North East) Limited | Transport & logistics | 2019 |
| 247 Community Care Limited | Health & social care | 2025 |
| 2M Equest Limited | Manufacturing | 1997 |
| 2TL Limited | Water & waste | 2021 |
| 3B Support Services Limited | Professional & scientific | 2016 |
| 477 Management Ltd | Construction | 2026 |
| 6IX Property Ltd | Real estate | 2020 |
| 6P Solutions Limited | Information & communication | 2015 |
| 908 Ltd | Wholesale & retail | 2006 |
| 9INTH Element Limited | Information & communication | 2003 |
| A & S Coding Ltd. | Professional & scientific | 2012 |
| A Brumwell Plastering Ltd | Construction | 2018 |
| A H Drywall Finishing Limited | Construction | 2018 |
| A J Flooring NE Ltd | Construction | 2025 |
| A.D. Scaffolding North East Limited | Wholesale & retail | 2009 |
| A.M.A Atvs Ltd | Wholesale & retail | 2025 |
| A.S.G.S. Limited | Wholesale & retail | 2003 |
| A.S.G.S. Property Limited | Real estate | 2019 |
| A1 Asphalt & Tarmacadam Surfacing Ltd | Construction | 1996 |
| A1 Ventilation Services Limited | Construction | 2017 |
| A2B Transit Ltd | Transport & logistics | 2011 |
| AA Dhillon Properties Ltd | Real estate | 2018 |
| AAB Conveyors Ltd | Manufacturing | 2014 |
| AAJ Motors Limited | Wholesale & retail | 2020 |
| Abercorn Properties Limited | Real estate | 2004 |
| Above the Water Limited | Education | 2019 |
| Absolute Civil Engineering Limited | Construction | 2008 |
| ACA GAS, Heating and Plumbing Ltd | Construction | 2021 |
| Accountants for the Trade (Durham) Limited | Professional & scientific | 2021 |
| Accountants for the Trade Limited | Professional & scientific | 2020 |
| Accurate Measurement Services Ltd | Professional & scientific | 2020 |
| Acgc Joinery Ltd | Construction | 2022 |
| Acgc Property Management Ltd | Real estate | 2023 |
| Acmi Engineering Ltd | Professional & scientific | 2025 |
| Active Future Durham CIC | Education | 2025 |
| Activedeluxewear Limited | Wholesale & retail | 2025 |
| AD Brumwell Plastering Ltd | Construction | 2025 |
| AD Design Studio Ltd | Professional & scientific | 2026 |
| AD Hold Co Limited | Financial services | 2023 |
| AD Venture Signs & Image Ltd | Manufacturing | 2020 |
| Adam Jackson Lettings Support Ltd | Administrative & support | 2026 |
| Adlex Limited | Real estate | 2009 |
| Advanced Protection North East Ltd | Administrative & support | 2024 |
| AE Walker Consulting Ltd | Professional & scientific | 2021 |
| Affiniti Properties Ltd | Real estate | 2022 |
| After Market Trading Ltd | Wholesale & retail | 2024 |
| AG Development Holdings Ltd | Financial services | 2022 |
| AGB & Co Properties Ltd | Real estate | 2019 |
| AH Events Group Ltd | Other services | 1987 |
| AHB Timber Ltd | Manufacturing | 2026 |
| Ai-Connect Solutions Ltd | Information & communication | 2023 |
| Airlie & James Consultants Ltd. | Administrative & support | 2011 |
| Airlie Leisure Limited | Hospitality | 2022 |
| AJ Piling Ltd | Construction | 2023 |
| AJL Solutions Ltd | Information & communication | 2025 |
| Ajne Property Limited | Real estate | 2021 |
| AK Rooster Ltd | Hospitality | 2026 |
| AKH Retail Limited | Wholesale & retail | 2014 |
| Alchemy Healthcare Group Limited | Professional & scientific | 2021 |
| Alder Investments Limited | Real estate | 2022 |
| Alecto Electrical and Building Contractors Limited | Extraterritorial | 2021 |
| Alexandra Rentals Ltd | Households | 2025 |
| Alimento's Ltd | Hospitality | 2025 |
| ALL North Development Ltd | Construction | 2021 |
| ALL That WE ARE Ltd | Professional & scientific | 2024 |
| Allely Eden Holdings Limited | Professional & scientific | 2006 |
| Alnside Associates Limited | Professional & scientific | 2009 |
| Alnsolutions Ltd | Administrative & support | 2022 |
| Alpha Boxing CIC | Education | 2025 |
| Alpha Property & Services Ltd | Transport & logistics | 2024 |
| Alpine Air Conditioning (NE) Limited | Energy | 2013 |
| Altitude Cellular & Broadcast Rigging Ltd | Information & communication | 2015 |
| Amario Global Security Ltd | Administrative & support | 2025 |
| Amethyst Homes (North East) Limited | Construction | 2021 |
| Amethyst Homes Limited | Construction | 2013 |
| Amion Ltd | Hospitality | 2023 |
| Amppath Ltd | Professional & scientific | 2025 |
| Amrena Homes Ltd | Real estate | 2025 |
| Amulya Aaradhya Limited | Real estate | 2024 |
| Amys Estates Ltd | Real estate | 2021 |
| Anchor Accommodation Limited | Hospitality | 2019 |
| Anderson & Metcalf Builders Limited | Construction | 2016 |
| Anderson & Pither Construction Ltd | Construction | 2021 |
| ANJ Ordnance Disposal Solutions Limited | Water & waste | 2023 |
| Anna Caygill Art Ltd | Construction | 2023 |
| Anthony Farnsworth Management Services Limited | Professional & scientific | 2014 |
| Anvil Homes (Construction Services) Limited | Construction | 2023 |
| Anvil Homes (Great Whittington) Limited | Construction | 2021 |
| Anvil Homes (North East) Limited | Construction | 2025 |
| Anvil Homes (North West) Limited | Construction | 2021 |
| Anvil Homes Limited | Construction | 1994 |
| Anya Kirkby Ltd | Arts & recreation | 2022 |
| Apex Bricklaying Services Limited | Construction | 2025 |
| Apex Housing Services Ltd | Real estate | 2018 |
| APM Access and Inspection Ltd | Professional & scientific | 2018 |