| Syfm Properties Limited | Real estate | 2026 |
| Symade Limited | Households | 2025 |
| Synaptic Systems Ltd | Information & communication | 2025 |
| Sync Payments Ltd | Other services | 2025 |
| System Consults Ltd | Information & communication | 2023 |
| T & H Cummings Ltd | Administrative & support | 2018 |
| T & N Healthcare Limited | Administrative & support | 2026 |
| T & W Builders Ltd | Construction | 2006 |
| T First Surveying and Building Ltd | Construction | 2025 |
| T Hildrew Welding Inspection Services Limited | Construction | 2015 |
| T J Willday Limited | Professional & scientific | 2014 |
| T P Bradbury Ltd | Other services | 2010 |
| T!Tan Event Management Ltd | Administrative & support | 2026 |
| T&J Barber Ltd | Other services | 2023 |
| T&J Construct NE Ltd | Construction | 2023 |
| T.K. Decor Limited | Construction | 2007 |
| T.M. Bewick Limited | Construction | 1979 |
| T31 Consultancy Ltd. | Manufacturing | 2016 |
| T5 Ltd | Real estate | 2025 |
| Taajouk Ltd | Wholesale & retail | 2021 |
| Taco Sunderland Ltd | Hospitality | 2025 |
| Tact Properties NE Ltd | Construction | 2025 |
| Tacticool Limited | Wholesale & retail | 2024 |
| TAG08 Ltd | Construction | 2023 |
| Tailored Metals Limited | Construction | 2023 |
| Tailored Property Enterprises Ltd | Real estate | 2004 |
| Tainui Platers Ltd | Manufacturing | 2024 |
| Taiya's Fish and Chips Ltd | Hospitality | 2024 |
| TAK Turkish Ltd | Other services | 2024 |
| Talent Entrainment Limited | Education | 2023 |
| Talis Technology Ltd | Administrative & support | 2020 |
| Talking Houses (NE) Ltd | Construction | 2017 |
| Talking Houses Nationwide Ltd | Education | 2023 |
| Tally HO Housing N.E. Ltd | Real estate | 2007 |
| Tamtas Beauty Limited | Professional & scientific | 2025 |
| Tamworth Delivery Ltd | Transport & logistics | 2020 |
| TAN Solo Ltd | Other services | 2019 |
| Tandem Construction Bidco Limited | Financial services | 2024 |
| Tandem Construction Holdings Limited | Financial services | 2024 |
| Tandem Construction Ltd | Construction | 2021 |
| Tandoori Club Ltd | Hospitality | 2020 |
| Tanerife Tanning and Beauty Salon Ltd | Other services | 2021 |
| Tango Bravo Limited | Financial services | 2024 |
| Tantastic Tanning & Beauty Studio Limited | Other services | 2014 |
| Tarbiz Ltd | Hospitality | 2025 |
| Target Planning Financial Services Limited | Financial services | 2010 |
| Targi Drug Limited | Administrative & support | 2022 |
| Tarro Limited | Hospitality | 2024 |
| Tasty Bite Town Ltd | Hospitality | 2026 |
| Tasty Foods NE Ltd | Hospitality | 2018 |
| Tasty Little Catering Ltd | Hospitality | 2026 |
| Tatham Events Ltd | Hospitality | 2023 |
| Tatton Properties (NE) Limited | Real estate | 2023 |
| Taunton Lettings Ltd. | Real estate | 2025 |
| Tavistock Press Limited | Manufacturing | 2008 |
| Tavistock Print Consultancy Ltd | Professional & scientific | 2017 |
| Tax Shop Accountants Ltd | Professional & scientific | 2013 |
| Taylor Commissioning Solutions Limited | Construction | 2025 |
| Taylor E, C & I Limited | Administrative & support | 2009 |
| Taylor Higgins Property Limited | Construction | 2020 |
| Taylors Waste Management Limited | Water & waste | 2022 |
| TAZ Properties Sunderland Ltd | Real estate | 2024 |
| Tazmania BBQ House Ltd | Hospitality | 2025 |
| TB Property & Lettings Ltd | Real estate | 2025 |
| TBM Contracts (NE) Ltd | Construction | 2018 |
| TBM Contracts Limited | Construction | 2008 |
| TCS NE Ltd | Professional & scientific | 2024 |
| TCT Developments (North East) Limited | Real estate | 2009 |
| TD Roker Limited | Hospitality | 2024 |
| TDW Design Ltd | Real estate | 2025 |
| Team Dynamic Coaching Community Interest Company | Health & social care | 2025 |
| Teamlawn Limited | Households | 2002 |
| Teasdale Project Innovations Ltd | Construction | 2024 |
| Tebk Limited | Administrative & support | 2023 |
| Technic Car Valeting Limited | Administrative & support | 2023 |
| Tectum Properties Ltd | Real estate | 2021 |
| Teesside Windfarm Limited | Energy | 2008 |
| Teeyworld Confectionery Limited | Manufacturing | 2025 |
| TEF Barber Ltd | Other services | 2026 |
| Teho Solutions Ltd | Wholesale & retail | 2025 |
| Tejosri Ltd | Wholesale & retail | 2024 |
| Tekkie Ltd | Information & communication | 2014 |
| Tekscope Limited | Construction | 2026 |
| Temp Accountants LLP | | 2024 |
| TEN Lindsay Court Limited | Extraterritorial | 2023 |
| TEN37 Ltd | Hospitality | 2021 |
| Tenants First C.I.C. | Other services | 2025 |
| Tench's Safety Solutions Limited | Professional & scientific | 2025 |
| Tender Care Health Solutions Ltd | Health & social care | 2023 |
| Tephra Ltd | Construction | 2018 |
| Tera RTM Company Limited | Households | 2026 |
| Terminus Properties Limited | Real estate | 2023 |
| Terragate Trading Ltd | Wholesale & retail | 2026 |
| Terrybit Ltd | Information & communication | 2021 |
| Tesmonard Europe Limited | Administrative & support | 1999 |
| Tesmonard North East Limited | Extraterritorial | 2009 |
| Tested Films Limited | Information & communication | 2010 |
| TGD Engineering Ltd | Professional & scientific | 2023 |
| TGL Properties (North East) Limited | Extraterritorial | 2016 |
| TGM (Holdings) Limited | Professional & scientific | 1993 |