| Scoutafi Ltd | Information & communication | 2024 |
| SCR Contracting Ltd | Construction | 2025 |
| Scrm Teesside Ltd | Real estate | 2024 |
| Scroll Breakers Ltd | Professional & scientific | 2026 |
| Sculpt.Hair Ltd | Other services | 2024 |
| Scyte Studios Ltd | Information & communication | 2025 |
| SD Comms (NE) Limited | Information & communication | 2019 |
| SD Consultancy (North East) Ltd | Financial services | 2017 |
| SD Engineering (NE) Limited | Professional & scientific | 2022 |
| SD Motors NE Ltd | Administrative & support | 2025 |
| SD Rigging & Lifting Ltd | Construction | 2025 |
| SD Rigging and Lifting Services Ltd | Professional & scientific | 2022 |
| Sd-Ne Ltd | Professional & scientific | 2024 |
| Sdefty Social Care Ltd | Health & social care | 2022 |
| SDG Properties (NE) Ltd | Real estate | 2020 |
| SDJ Catering Ltd | Hospitality | 2024 |
| SDJ Jointing Ltd | Construction | 2026 |
| Sdjenkins Consulting Ltd | Professional & scientific | 2020 |
| SE Construction Management Ltd | Construction | 2025 |
| Seah Wind Ltd. | Manufacturing | 2021 |
| Sealpump Engineering Limited | Wholesale & retail | 1979 |
| Sealtight Windows (N E) Limited | Manufacturing | 1998 |
| Seamer Construction Limited | Construction | 2017 |
| Seamer Consult Limited | Professional & scientific | 2022 |
| Seamer UK Limited | Administrative & support | 2012 |
| Sean Hammond Inspection Ltd | Construction | 2008 |
| Sean Hugill Joinery & Building Ltd | Construction | 2023 |
| Sebastian Knight Ltd | Real estate | 2018 |
| Sec-Sol Limited | Administrative & support | 2018 |
| SEC14 Ltd | Administrative & support | 2026 |
| Securt Ltd | Administrative & support | 2025 |
| Securus Planning Ltd | Financial services | 2015 |
| Seda Cleaning Solutions Ltd | Administrative & support | 2021 |
| Sedecim 96 Limited | Manufacturing | 2025 |
| Sedgefield Commercials Limited | Wholesale & retail | 2012 |
| Sedgewick Studios Ltd | Professional & scientific | 2019 |
| Sedgwick Property Ltd | Real estate | 2021 |
| Seerbi Ltd | Information & communication | 2021 |
| Sefnia Ltd | Wholesale & retail | 2023 |
| Sehc Consultancy Limited | Professional & scientific | 2003 |
| Sejad AL Properties Ltd | Real estate | 2025 |
| Sekoia Services Ltd | Wholesale & retail | 2017 |
| Select Dental Care Limited | Health & social care | 2025 |
| Select Equestrian Services LLP | | 2011 |
| Selerno Pizza Ltd | Hospitality | 2018 |
| Selfish Fine Soaps Ltd | Manufacturing | 2023 |
| Selkirk Properties Limited | Real estate | 1997 |
| Sell a Property Ltd | Real estate | 2021 |
| Sell Your Property Fast (North East) Ltd | Real estate | 2023 |
| Selvie Ltd | Wholesale & retail | 2025 |
| Sema International Ltd | Wholesale & retail | 2022 |
| Sembcorp (Wilton Bess) Limited | Energy | 2023 |
| Sembcorp Energy UK Limited | Energy | 2018 |
| Sembcorp Holdings Limited | Professional & scientific | 2008 |
| Sembcorp Investments (China) Limited | Professional & scientific | 2009 |
| Sembcorp Utilities (UK) Limited | Manufacturing | 2003 |
| Sembcorp Utilities Services Limited | Professional & scientific | 1999 |
| Sembcorp Utilities Teesside Pension Trustees Limited | Professional & scientific | 2003 |
| Semley Industrial Services Ltd | Energy | 2025 |
| SEN Experts (North East) Limited | Education | 2022 |
| Senecazero Ltd | Information & communication | 2025 |
| Senior Wags NE Limited | Manufacturing | 2025 |
| Senshi Street Food Ltd | Hospitality | 2019 |
| Sensory Storytime Limited | Education | 2021 |
| Senturion Ltd | Extraterritorial | 2019 |
| SEP Culant Civil Engineering Ltd | Construction | 2023 |
| SEP Culant Ltd | Professional & scientific | 2011 |
| SEP Drainage Ltd | Water & waste | 2024 |
| SEP Ecology Ltd | Professional & scientific | 2024 |
| SEP Infrastructure Ltd | Construction | 2024 |
| SEP Monitoring & Civils Ltd | Construction | 2025 |
| SEP NE Limited | Real estate | 2024 |
| SEP Rail Services Ltd | Professional & scientific | 2018 |
| Sephora Hair Extensions Limited | Other services | 2014 |
| Seqens UK Limited | Professional & scientific | 2017 |
| Seraphim Northern Limited | Professional & scientific | 2025 |
| Serban Painters Ltd | Construction | 2022 |
| Serendipity Hairdressing Limited | Other services | 2012 |
| Serendipity Shelters Ltd | Real estate | 2021 |
| Serene Shades Limited | Administrative & support | 2025 |
| Serenity Square Ltd | Wholesale & retail | 2026 |
| Sergio & Melissa Limited | Hospitality | 2011 |
| Sergomd Ltd | Transport & logistics | 2024 |
| Sernor Ltd | Information & communication | 2022 |
| Service Cleaning RAM Ltd | Administrative & support | 2025 |
| Seugi Limited | Wholesale & retail | 2026 |
| Seven Innovation and Design Ltd | Manufacturing | 2022 |
| Seventh Vision Limited | Wholesale & retail | 2026 |
| SEW Safe Ltd | Manufacturing | 2019 |
| Sewells Car Parts Ltd | Wholesale & retail | 2023 |
| SF Property Fitout Ltd | Construction | 2026 |
| SFG Technical Limited | Administrative & support | 2016 |
| Sfkm Consulting Limited | Professional & scientific | 2008 |
| SFS Designs Ltd | Professional & scientific | 2021 |
| SG Automation Ltd | Professional & scientific | 2010 |
| SG Rail NE Ltd | Manufacturing | 2014 |
| SG2 Middlesbrough Limited | Hospitality | 2014 |
| SGB Digital Ltd | Wholesale & retail | 2025 |
| SGB Residential Lettings Ltd | Real estate | 2021 |
| SGD Mechanical Services Ltd | Construction | 2019 |