| Stiroko Ltd | Wholesale & retail | 2026 |
| Stitch Express Limited | Wholesale & retail | 2008 |
| STL Recovery Ltd | Wholesale & retail | 2017 |
| STM Property and Development Limited | Real estate | 2024 |
| Stmc Equiptech Services Ltd | Manufacturing | 2026 |
| Stockcheck Northeast Limited | Professional & scientific | 2006 |
| Stockdale Financial Solutions Limited | Administrative & support | 2015 |
| Stockton Catering Ltd | Hospitality | 2019 |
| Stoker Property Ltd | Construction | 2025 |
| Stoker Property Residential Limited | Real estate | 2024 |
| Stonehouse Consultancy Ltd | Professional & scientific | 2020 |
| Stop & Shop Sunderland Ltd | Wholesale & retail | 2024 |
| Storeys DDR Holdings Limited | Financial services | 2023 |
| Storeys DDR Ltd | Health & social care | 2018 |
| STR Connect Limited | Construction | 2024 |
| Straight Talking HR Limited | Administrative & support | 2024 |
| Strangers by Nature Ltd | Wholesale & retail | 2026 |
| Strassenbau Ltd | Construction | 2026 |
| Stratadrive Ltd | Education | 2025 |
| Stratavault Infrastructure Ltd | Construction | 2026 |
| Strategic Service Partners Limited | Professional & scientific | 2026 |
| Stratton Distribution Ltd | Wholesale & retail | 2023 |
| Stratton Estates UK 1 Ltd | Construction | 2025 |
| Stratus Global Ltd | Extraterritorial | 2016 |
| Stream Healthcare Ltd | Health & social care | 2024 |
| Streamboost Ltd | Professional & scientific | 2026 |
| Street Hassle Ltd | Hospitality | 2019 |
| Strength and Balance CIC | Other services | 2026 |
| Strength and Movement Project CIC | Other services | 2025 |
| Stress Less 4 Wellness CIC | Health & social care | 2023 |
| Strictly Bricks Ltd | Construction | 2021 |
| Strictly Restaurants Ltd | Other services | 2024 |
| Stride IT Solutions Ltd | Information & communication | 2026 |
| Strolls With Poles Community Interest Company | Other services | 2023 |
| Strong Guard Security North East Ltd | Administrative & support | 2024 |
| Stronger Than Hunger Ltd | Wholesale & retail | 2025 |
| STS Electricals (North East) Limited | Construction | 2019 |
| STS Marine Solutions (UK) Limited | Transport & logistics | 1984 |
| Stubbs Electrical Services Ltd | Construction | 2017 |
| Student Accommodation Services (Sunderland) Limited | Extraterritorial | 2012 |
| Student Accommodation Services Limited | Real estate | 2004 |
| Student Accommodation Sunderland Limited | Extraterritorial | 2016 |
| Student City Ltd | Real estate | 2015 |
| Studio B Clothing Limited | Wholesale & retail | 2025 |
| Studio Bloom (NE) Ltd | Other services | 2023 |
| Studio Muiz Limited | Information & communication | 2025 |
| Studylink Global Ltd | Education | 2025 |
| Subat Ltd | Wholesale & retail | 2024 |
| Subsea Ltd | Professional & scientific | 2022 |
| Succession Law Consultancy Ltd | Professional & scientific | 2011 |
| Succession Law Limited | Professional & scientific | 2018 |
| SUE Young Aesthetics Ltd | Health & social care | 2017 |
| Sugar Hair Extensions Ltd | Other services | 2020 |
| Sugar M Limited | Hospitality | 2024 |
| Sultan Halal Foodstore Ltd | Wholesale & retail | 2017 |
| Summerlee Property Services Ltd | Construction | 2023 |
| Summerson Homes Ltd | Construction | 2025 |
| Sumner & Johnson Hair Ltd | Other services | 2022 |
| Sun Building Sunderland Ltd | Real estate | 2025 |
| Sun Tanning Co Sunderland Limited | Other services | 2024 |
| Sun'Lun Sorted CIC | Health & social care | 2026 |
| Sunderland Accommodation Services Limited | Real estate | 2004 |
| Sunderland Afc.Com Limited | Professional & scientific | 2000 |
| Sunderland African Community Association (Saca) Community Interest Company | Other services | 2024 |
| Sunderland Antiquarian Society | Arts & recreation | 2023 |
| Sunderland Area Parent Support Limited | Information & communication | 2008 |
| Sunderland Association Football Club Women Limited | Arts & recreation | 2013 |
| Sunderland at 180 RTM Company | Households | 2025 |
| Sunderland Ballet CIC | Education | 2022 |
| Sunderland Bangladesh International Centre Limited | Other services | 1999 |
| Sunderland BID Limited | Other services | 2013 |
| Sunderland Business Ltd | Other services | 2012 |
| Sunderland Care and Support (Holding Company) Limited | Health & social care | 2013 |
| Sunderland Care and Support Limited | Health & social care | 2013 |
| Sunderland Carers Centre | Other services | 2006 |
| Sunderland Carpet Centre Limited | Wholesale & retail | 2020 |
| Sunderland Cat & Dog Rescue Ltd | Other services | 2014 |
| Sunderland City Housing Ltd | Real estate | 2023 |
| Sunderland Coachworks 2 Ltd | Wholesale & retail | 2008 |
| Sunderland College Enterprises Limited | Administrative & support | 2015 |
| Sunderland Community Action Group CIC | Professional & scientific | 2015 |
| Sunderland Community Support Pantry CIC | Health & social care | 2024 |
| Sunderland Counselling Service | Health & social care | 1997 |
| Sunderland Creative Business Hub Limited | Real estate | 2019 |
| Sunderland Culture Limited | Arts & recreation | 2016 |
| Sunderland Culture Trading Ltd | Arts & recreation | 2021 |
| Sunderland Deaf Centre Trading Limited | Hospitality | 2005 |
| Sunderland Dene Limited | Hospitality | 2026 |
| Sunderland Digital Radio Community Interest Company | Information & communication | 2024 |
| Sunderland East Arts & Music Ltd | Arts & recreation | 2019 |
| Sunderland Electrical Network Ltd | Information & communication | 2025 |
| Sunderland Empire Theatre Trust | Arts & recreation | 1973 |
| Sunderland Enterprise Park Management Company Limited | Administrative & support | 1994 |
| Sunderland Fade Zone Ltd | Other services | 2026 |
| Sunderland Fast Foods Limited | Hospitality | 2015 |
| Sunderland FC Development LLP | | 2012 |
| Sunderland FC Hotels Limited | Hospitality | 2013 |
| Sunderland Fencing and Landscaping Ltd | Wholesale & retail | 2021 |
| Sunderland Foyboatmen Dock Labour Ltd | Transport & logistics | 2013 |
| Sunderland Furniture Warehouse Limited | Transport & logistics | 2018 |