| Scholarsphere Ltd | Information & communication | 2023 |
| School of Polish Language and Culture Community Interest Company | Education | 2018 |
| Schwartz Patrick Media Ltd | Information & communication | 2019 |
| Science Buddies Limited | Education | 2017 |
| Scint Fish Ltd | Arts & recreation | 2025 |
| Scissorguys Ltd | Other services | 2018 |
| SCL Joinery & Interiors Ltd | Construction | 2020 |
| Scls Consultants Ltd | Professional & scientific | 2019 |
| Scobell Properties Limited | Real estate | 2021 |
| Scollen & Wright Funeral Service Limited | Other services | 2009 |
| Scope Capital Ltd | Real estate | 2026 |
| Scott Emmerson Electricals Ltd | Construction | 2026 |
| Scott Haley Building Services Ltd | Construction | 2018 |
| Scott Hire (N.E.) Ltd | Construction | 2018 |
| Scott Pattison Limited | Construction | 2015 |
| Scott Safety Supplies Ltd | Other services | 2019 |
| Scott Spock & KO Ltd | Professional & scientific | 2019 |
| Scotties Lock Inn Limited | Hospitality | 2025 |
| Scranz Ltd | Hospitality | 2025 |
| Screech Ltd | Information & communication | 2025 |
| SCS Furnishings Limited | Professional & scientific | 1996 |
| SCS Group Limited | Wholesale & retail | 1996 |
| Scugnizzi Ltd | Hospitality | 2019 |
| Scurfa Ltd | Wholesale & retail | 2013 |
| SD Lettings North East Ltd | Real estate | 2026 |
| SD Mentoring UK Limited | Professional & scientific | 2022 |
| SD Property North East Limited | Real estate | 2024 |
| SD SIM Training Ltd | Education | 2026 |
| SDL Access Ltd | Other services | 2024 |
| Sea Road Fisheries Limited | Hospitality | 2018 |
| Seaburn Beach Cafe Limited | Hospitality | 2016 |
| Seaburn Decor Ltd | Administrative & support | 2017 |
| Seaburn GAS Services Limited | Construction | 2008 |
| Seaburn Marketing Ltd | Wholesale & retail | 2016 |
| Seaburndene 168 Limited | Hospitality | 2024 |
| Seafarers Catering Ltd | Hospitality | 2024 |
| Seafront Pizzeria Ltd | Hospitality | 2019 |
| Seaham Beauty Ltd | Other services | 2019 |
| Sealprosealants Ltd | Construction | 2025 |
| Seamus Omargh Limited | Professional & scientific | 2018 |
| Seascape Consulting Limited | Professional & scientific | 2020 |
| Seasonal Activities Ltd | Arts & recreation | 2025 |
| Seasons Made Easy Ltd | Wholesale & retail | 2025 |
| Secon Holdings Limited | Wholesale & retail | 2017 |
| Secon Solar Limited | Wholesale & retail | 2003 |
| Second Chance Sunderland CIC | Wholesale & retail | 2023 |
| Second Draft Ltd | Information & communication | 2017 |
| Secret Fame Limited | Wholesale & retail | 2021 |
| Secure Future Property Ltd | Real estate | 2025 |
| Secureai Guard Limited | Information & communication | 2025 |
| Security 2000 (Northeast) Ltd | Administrative & support | 2012 |
| Security Resourcing Ltd | Administrative & support | 2024 |
| SEE IF Place Deliveries Ltd | Transport & logistics | 2025 |
| Seeds of Change Sunderland C.I.C. | Professional & scientific | 2021 |
| Sehmbis Trade Ltd | Other services | 2020 |
| Sela Soils Limited | Professional & scientific | 2021 |
| Selcray Limited | | 1977 |
| Seldons Leisureworld Limited | Extraterritorial | 2015 |
| Select Car Centre N E Ltd | Wholesale & retail | 2012 |
| Select Catering (Sunderland) Ltd | Hospitality | 2014 |
| Select Property Management NE Limited | Real estate | 2012 |
| Self Medical Aesthetics Ltd | Public administration | 2023 |
| Self Medical Training Ltd | Public administration | 2026 |
| Selomar Limited | Wholesale & retail | 2018 |
| Sendelight Gifts Ltd | Wholesale & retail | 2024 |
| Senin Foods Ltd | Wholesale & retail | 2026 |
| Senko Europe Ltd | Professional & scientific | 2018 |
| Senso Pro Ltd | Manufacturing | 2024 |
| SEP Shaz Ltd | Administrative & support | 2019 |
| Septar Ltd | Transport & logistics | 2019 |
| September Innovations Limited | Information & communication | 2008 |
| Serdar Eslan Ltd | Wholesale & retail | 2025 |
| Serein Wellness Ltd | Health & social care | 2025 |
| Serenia OIL Trading and Shipping Services Limited | Wholesale & retail | 2017 |
| Seriously Greener Ltd | Construction | 2020 |
| SES Physiotherapy Ltd | Health & social care | 2018 |
| Setting OUT Services (North East) Ltd | Professional & scientific | 2014 |
| Seun Tech Ltd | Information & communication | 2024 |
| Sexy and Symptomatic Ltd | Health & social care | 2024 |
| Sexy Nails Sunderland Ltd | Other services | 2025 |
| Sezrfashion.Com Limited | Wholesale & retail | 2023 |
| SF Vintage Ltd | Wholesale & retail | 2023 |
| SGB2026 Limited | Administrative & support | 2024 |
| SGD Properties Ltd | Real estate | 2026 |
| SGN Consultants Limited | Wholesale & retail | 2023 |
| SGP Installation Services Ltd | Construction | 2009 |
| Sgpa Clinical Services Limited | Health & social care | 2018 |
| SGV Signs Limited | Professional & scientific | 2012 |
| SH Keyrings Limited | Wholesale & retail | 2018 |
| SH Seafoods Limited | Agriculture & fishing | 2017 |
| Shaa Kurdish Restaurant Limited | Hospitality | 2025 |
| Shabaz Sana Ltd | Hospitality | 2026 |
| Shad Sultan Limited | Hospitality | 2018 |
| Shadow Response Ltd | Administrative & support | 2025 |
| Shahi Properties Management Limited | Households | 2025 |
| Shahichai Limited | Hospitality | 2025 |
| Shaka Camera Services Ltd | Information & communication | 2018 |
| Shakespeare Cast Products Limited | Manufacturing | 2020 |
| Shakespeare Inspection Services Limited | Professional & scientific | 2024 |
| Shakin’ Paradise Ltd | Wholesale & retail | 2024 |