| Stao Ltd | Financial services | 2015 |
| Star Barber Durham Ltd | Other services | 2025 |
| Starkold Assets Ltd | Financial services | 2024 |
| Starkold Holdings Ltd | Construction | 2024 |
| Starkold Properties Ltd | Real estate | 2024 |
| Starstruck Holdings Limited | Financial services | 2021 |
| Starstruck Limited | Real estate | 2001 |
| Start People Group Ltd | Administrative & support | 2025 |
| Start People Limited | Administrative & support | 2014 |
| Starway Leisure Limited | Hospitality | 1997 |
| Staryl Services Ltd | Transport & logistics | 2025 |
| Station 211 Ltd | Information & communication | 2023 |
| Stay Urban Ltd | Real estate | 2023 |
| Stdmax Ltd | Wholesale & retail | 2025 |
| Steel Town Properties Limited | Financial services | 2023 |
| Steele Property Trading Ltd | Real estate | 2025 |
| Stelia Media Ltd | Information & communication | 2018 |
| Stellae Leisure Ltd | Hospitality | 2016 |
| Stemeup Ltd | Education | 2025 |
| Stephen Fenty LLP | | 2019 |
| Stephen King Consultancy Limited | Professional & scientific | 2024 |
| Stephen Richardson Roofing Services Limited | Construction | 2005 |
| Stephen Thompson Civil Engineering Ltd | Construction | 2016 |
| Stephenson Partnership LLP | | 2011 |
| Stephenson-Mohl Development Ltd | Construction | 2018 |
| Stepping Stones Day Nursery (Durham) Limited | Health & social care | 2011 |
| Stepping Stones Mediation Limited | Professional & scientific | 2002 |
| Sterling Cross Holdings Limited | Financial services | 2024 |
| Steve Howey Limited | Arts & recreation | 2014 |
| Steven Gregory Designs Limited | Manufacturing | 2007 |
| Steven Harrison Brickworks Ltd | Construction | 2018 |
| Stewart Legg & Company Ltd | Hospitality | 2019 |
| Stick Marketing Limited | Professional & scientific | 2020 |
| Still in Businesss Limited | Education | 2016 |
| Stivano's Pizza Plus Ltd | Hospitality | 2022 |
| STL Cabs Ltd | Transport & logistics | 2022 |
| Stmlc Ltd | Professional & scientific | 2011 |
| Stobbilee.Com Limited | Real estate | 2023 |
| Stocksight Ltd | Information & communication | 2025 |
| Stoic Software Ltd | Information & communication | 2025 |
| Stone Island Ltd | Real estate | 2021 |
| Stonebake Durham Limited | Hospitality | 2023 |
| Stonebridge (NE) Capital Limited | Professional & scientific | 2024 |
| Stoneyworks Ltd | Professional & scientific | 2017 |
| Storage Spot Ltd | Transport & logistics | 2020 |
| Stormin' the Castle Limited | Administrative & support | 1998 |
| Stovetastic Ltd | Wholesale & retail | 2025 |
| Straight BAT Advice Limited | Professional & scientific | 2023 |
| Straight BAT Properties Limited | Real estate | 2021 |
| Strategic Pre-Clinical Product Development Limited | Professional & scientific | 2014 |
| Strathmore Holdings Limited | Construction | 2002 |
| Strathmore Homes Limited | Construction | 2002 |
| Stratobayes Limited | Information & communication | 2026 |
| Strawberry Hill Farm Limited | Hospitality | 2017 |
| Strawbridge Strength & Performance Limited | Wholesale & retail | 2024 |
| Stray AID Trading AS Durham Dogs and Cats Home Ltd | Administrative & support | 2006 |
| Stray Care Services Ltd | Professional & scientific | 2022 |
| Streamliners UK Limited | Professional & scientific | 2018 |
| Streem Connect Limited | Information & communication | 2021 |
| Streemline Limited | Professional & scientific | 2024 |
| Stride PR Ltd | Professional & scientific | 2016 |
| Strive Durham Ltd | Education | 2023 |
| Stuart Bradley Plant Hire Limited | Construction | 2009 |
| Stuart Marley Limited | Construction | 2018 |
| Stuart Wright Funeral Service Limited | Other services | 2003 |
| Stuart Wright Holdings Limited | Financial services | 2025 |
| Studio PPL Ltd | Professional & scientific | 2025 |
| Su&Ka Global Ltd | Wholesale & retail | 2025 |
| SUB Rosa Holdings Ltd | Real estate | 2025 |
| SUB Rosa Trading Ltd | Hospitality | 2025 |
| Substruct Civils Ltd | Construction | 2022 |
| Success Ignition Ltd | Information & communication | 2020 |
| Success Kickstart Limited | Wholesale & retail | 2013 |
| SUE Rice Ltd | Hospitality | 2023 |
| Sugar Beach 2 Limited | Financial services | 2025 |
| Sugar Tree Limited | Real estate | 2022 |
| Suggitt Enterprises Limited | Wholesale & retail | 2015 |
| Sumesk Limited | Wholesale & retail | 2024 |
| Summer Social Work Ltd | Health & social care | 2023 |
| Summerleaze Investments Limited | Real estate | 2022 |
| Summit UK 001 Limited | Real estate | 2025 |
| Summit UK 002 Limited | Real estate | 2025 |
| Summit UK 003 Limited | Real estate | 2025 |
| Summit UK 004 Limited | Real estate | 2026 |
| Summit UK 005 Limited | Real estate | 2026 |
| Summit UK Group Limited | Real estate | 2025 |
| Summit UK Property Limited | Real estate | 2023 |
| Sun Tanning Co Ltd | Other services | 2023 |
| Sun Tanning Co Seaham Limited | Other services | 2025 |
| Sunderland Smartzone Limited | Transport & logistics | 2015 |
| Sung Global Ltd | Wholesale & retail | 2025 |
| Sungtech Trade Ltd | Wholesale & retail | 2026 |
| Sunlight Limited | Real estate | 2017 |
| Sunners Northeast Ltd | Wholesale & retail | 2014 |
| Sunny Bank Farm Limited | Financial services | 2019 |
| Sure Communication Limited | Information & communication | 2017 |
| Surtec (North East) Limited | Professional & scientific | 2002 |
| Surtees Enterprises Ltd | Financial services | 2025 |
| Surtees Equine Ltd | Real estate | 2025 |
| Surtees Transport Ltd | Transport & logistics | 2025 |