| Short Stay PAD Limited | Hospitality | 2020 |
| Shoshanim Ltd | Health & social care | 2018 |
| Show Productions Limited | Arts & recreation | 2016 |
| Show Productions Worldwide Ltd | Arts & recreation | 2019 |
| Shree Rameshwaram Ltd | Health & social care | 2026 |
| Shri Chandi Property Limited | Real estate | 2021 |
| Shropshire Surgery and Imaging Limited | Health & social care | 2019 |
| Siblings Nurseries North East Ltd | Education | 2014 |
| Side by Side Arts CIC | Arts & recreation | 2018 |
| Sidham Investments Limited | Real estate | 2024 |
| Sienna Harrison Limited | Construction | 2019 |
| SIG Combibloc Limited | Administrative & support | 1973 |
| Sigma Fire Ltd | Professional & scientific | 2012 |
| Sigma Holdings Limited | Professional & scientific | 1983 |
| Signal Plastic Components Limited | Manufacturing | 2012 |
| Signal Plastics Holdings Limited | Professional & scientific | 2006 |
| Signature Creations North East Limited | Professional & scientific | 2024 |
| Signature Vans Direct Limited | Wholesale & retail | 2016 |
| Signeffex Limited | Professional & scientific | 2015 |
| Silicon Intelligence Genesis Ltd | Information & communication | 2021 |
| Silk Properties Ltd | Real estate | 2021 |
| Silly Goose Sock Co Ltd | Wholesale & retail | 2025 |
| Silver Bayis Ltd | Real estate | 2023 |
| Silver Bricks Properties Limited | Real estate | 2022 |
| Silver Commerce Limited | Wholesale & retail | 2019 |
| Silver Lakes Music Ltd | Arts & recreation | 2023 |
| Silver Mews Limited | Health & social care | 2020 |
| Silver Spur Consultancy Limited | Professional & scientific | 2018 |
| Silver Spur Property Ltd | Real estate | 2020 |
| Silverham Limited | Manufacturing | 2002 |
| Silverlight Contracting Limited | Information & communication | 2017 |
| Sim's Kitchen Limited | Hospitality | 2019 |
| Simcha Investments Limited | Extraterritorial | 2011 |
| Sime Durham Properties Ltd | Real estate | 2018 |
| Simon Hawkins Consultancy Limited | Professional & scientific | 2010 |
| Simon James Cardiology Limited | Health & social care | 2026 |
| Simon James Consultants Limited | Information & communication | 2006 |
| Simple Bridging (UK) Limited | Financial services | 2014 |
| Simple Bridging CF Ltd | Financial services | 2023 |
| Simple Bridging HT Limited | Financial services | 2024 |
| Simple Bridging LOP Ltd | Financial services | 2021 |
| Simple Bridging NE Ltd | Financial services | 2021 |
| Simple Bridging SH Ltd | Financial services | 2021 |
| Simply Cheesecake Ltd | Manufacturing | 2019 |
| Simpson's Properties Ltd | Real estate | 2015 |
| Sims Web Solutions Ltd | Information & communication | 2021 |
| Sindha Retail Ltd | Wholesale & retail | 2026 |
| Sing UP | Extraterritorial | 2012 |
| Sing UP Foundation | Education | 2016 |
| Sing UP Group Limited | Education | 2016 |
| Sing WAH Dunston Ltd | Hospitality | 2024 |
| Singleton House Ltd | Real estate | 2020 |
| Siorra Ltd | Arts & recreation | 2025 |
| Sippafrica Ltd | Hospitality | 2024 |
| Site Fuel Ltd | Wholesale & retail | 2026 |
| SIX Thirteen Ltd | Real estate | 2018 |
| SIX Thirteen NO 2 Ltd | Real estate | 2018 |
| Sixthirteen Property Services Ltd | Real estate | 2019 |
| SIZ Limited | Other services | 2015 |
| SJ Property Management NE Ltd | Real estate | 2025 |
| SJM North East Limited | Professional & scientific | 2019 |
| SJP House 2 Home Ltd | Construction | 2026 |
| SJS Investments Ltd | Real estate | 2018 |
| SJT Management & Consulting Limited | Professional & scientific | 2026 |
| Sk's Local Ltd | Wholesale & retail | 2023 |
| Skan Property Limited | Real estate | 2024 |
| Skgd Ltd | Professional & scientific | 2022 |
| Skills 4 Work (Gateshead) Limited | Other services | 2014 |
| Skills Office Network Ltd | Professional & scientific | 2017 |
| Skills Training Academy Limited | Education | 2014 |
| Skinkemistryuk Ltd | Wholesale & retail | 2024 |
| Skirzynska-Podgorska Ltd | Health & social care | 2016 |
| Skkj Limited | Real estate | 2024 |
| Skoda Ltd | Real estate | 2023 |
| Skua Quality Limited | Professional & scientific | 2024 |
| Skunkworks Studios Ltd | Arts & recreation | 2024 |
| SKV Building Services Ltd | Construction | 2026 |
| Skyejo Limited | Real estate | 2022 |
| Skyro Ltd | Wholesale & retail | 2026 |
| SL Consulting North East Ltd | Professional & scientific | 2022 |
| SL Properties (North East) Ltd | Real estate | 2024 |
| SL Tiling (NE) Ltd | Construction | 2026 |
| Slade Autos Limited | Wholesale & retail | 2014 |
| Sleekburn Land & Buildings Ltd | Real estate | 2024 |
| Sleeky Group Limited | Financial services | 2023 |
| Sleeky Limited | Real estate | 2023 |
| Sleeky Web Design & Print Limited | Professional & scientific | 2011 |
| SLF NE Ltd | Construction | 2026 |
| Slick Mobile Valets and Detailing Limited | Other services | 2024 |
| SLN Medical Consultancy Limited | Health & social care | 2013 |
| Sloane Square House Residents Company Limited | Households | 1982 |
| Sloc Distribution Ltd | Wholesale & retail | 2025 |
| Slug Busters Ltd | Manufacturing | 2018 |
| Slyman & Rosy Properties Limited | Real estate | 2025 |
| SM Toraub Ltd | Health & social care | 2025 |
| SM4RT Ltd | Wholesale & retail | 2023 |
| SMA Properties NE Ltd | Real estate | 2021 |
| Small World Cafe Limited | Hospitality | 2024 |
| Smallmatter's Fitness Focus C.I.C. | Arts & recreation | 2023 |
| Smallwood Technical Services Ltd | Construction | 2012 |