| Smalltek Ltd | Professional & scientific | 2021 |
| Smart Auto Financial Services Ltd | Financial services | 2017 |
| Smart Brown Dog Ltd | Professional & scientific | 2013 |
| Smart Choice Digital Ltd | Information & communication | 2025 |
| Smart Launderette & Linen Hire Limited | Other services | 2022 |
| Smart Local Shop Ltd | Wholesale & retail | 2020 |
| Smart Power and GAS Ltd | Professional & scientific | 2024 |
| Smart Project Group UK Ltd | Construction | 2021 |
| Smart School Websites Limited | Information & communication | 2020 |
| Smart Spray Solutions Ltd | Construction | 2020 |
| Smartvend Systems Ltd | Wholesale & retail | 2023 |
| Smarty Stuffs Limited | Information & communication | 2023 |
| Smelbad Ltd | Wholesale & retail | 2025 |
| Smilte Restaurant (Harlow) Ltd | Hospitality | 2021 |
| Smilte Restaurant Limited | Hospitality | 2007 |
| Smith & Allan Holdings Ltd | Real estate | 2013 |
| Smith & Allan Ltd | Wholesale & retail | 2017 |
| Smiths Arms Ltd | Hospitality | 2019 |
| SMJ Precision Ltd | Administrative & support | 2016 |
| SMR North East Holdings Ltd | Administrative & support | 2025 |
| SMT NE Limited | Other services | 2026 |
| SN Social Limited | Information & communication | 2024 |
| Snaculf Consulting Ltd | Information & communication | 2026 |
| Snapcode Ltd | Extraterritorial | 2024 |
| SNB Consulting Group Ltd | Administrative & support | 2023 |
| Snip & Snip Barber Shop Ltd | Other services | 2023 |
| Snow Hall Events Limited | Real estate | 2026 |
| Snow Hall Limited | Hospitality | 2018 |
| Snowdon Family Properties Limited | Professional & scientific | 2026 |
| SNS Flooring Ltd | Wholesale & retail | 2025 |
| Snuggly Stitches Ltd | Manufacturing | 2025 |
| SO Kate Cosmetics Ltd | Other services | 2017 |
| SO Smart UK Ltd | Wholesale & retail | 2019 |
| Sockburn Estates LLP | | 2025 |
| Sockburn Partnership LLP | | 2025 |
| Sofil UK Ltd | Professional & scientific | 2013 |
| Sofit (Woodworking Machinery) Ltd | Extraterritorial | 2019 |
| Soft Intelligence Data Centre Ltd. | Information & communication | 2016 |
| Solar Skytech Ltd | Construction | 2024 |
| Solecare Clinic Ltd | Health & social care | 2011 |
| Solutions in Technology (IT) Limited | Information & communication | 2008 |
| Solutions in Technology Limited | Information & communication | 2005 |
| Somal Real Estate Ltd | Real estate | 2024 |
| Somnium (NE) Limited | Real estate | 2025 |
| Sora Interiors Ltd | Professional & scientific | 2025 |
| Sorour Trading Ltd | Wholesale & retail | 2025 |
| Sosha Foods Ltd | Hospitality | 2019 |
| Soteria Children's Services Group Limited | Health & social care | 2022 |
| Soti Stores Limited | Wholesale & retail | 2023 |
| South Durham Society of Model Engineers | Arts & recreation | 2000 |
| South Parade Amenity Woodland Limited | Extraterritorial | 2010 |
| South Quay Surgical Limited | Health & social care | 2019 |
| South Tees Developments Limited | Real estate | 2019 |
| South Tees Site Company (Stsc) Employee Trust Limited | Other services | 2019 |
| South Tees Site Company Limited | Real estate | 2016 |
| South View Racing Limited | Administrative & support | 2005 |
| Southacres Leisure Ltd | Other services | 2021 |
| Southacres Ltd | Agriculture & fishing | 2018 |
| Southbank Coaching Academy Ltd | Extraterritorial | 2022 |
| Sovi Online Limited | Wholesale & retail | 2025 |
| Soylent Solutions Limited | Information & communication | 2013 |
| Sozo Marketing Limited | Hospitality | 2023 |
| SP Dental Ltd | Health & social care | 2016 |
| SP Jameson Ltd | Professional & scientific | 2017 |
| SP5 Projects Limited | Professional & scientific | 2026 |
| Sparta Commercial Cleaning Limited | Administrative & support | 2017 |
| Sparta Security on Demand Ltd | Administrative & support | 2025 |
| SPC Online Training Academy Limited | Education | 2016 |
| Special Graces Company Limited | Health & social care | 2012 |
| Specialist Blasting Services Ltd | Professional & scientific | 2009 |
| Specialist Coatings Limited | Administrative & support | 1993 |
| Specialist Reporting Services Limited | Health & social care | 2016 |
| Specialist Training Services Limited | Information & communication | 2020 |
| Specta Global Ltd | Wholesale & retail | 2020 |
| Speech Buddies Limited | Health & social care | 2025 |
| Speedmalt International Ltd | Wholesale & retail | 2015 |
| Speedy Deliveries Ltd | Transport & logistics | 2026 |
| Speedy Entertainment Ltd | Information & communication | 2019 |
| Spice Island Takeaway Darlington Limited | Hospitality | 2005 |
| Spicenbox Limited | Hospitality | 2025 |
| Spicy Roller Ltd | Hospitality | 2024 |
| Spinberry UK Limited | Information & communication | 2021 |
| Spine Realign Limited | Other services | 2024 |
| Splendour Construction Limited | Construction | 2011 |
| Spontly Ltd | Information & communication | 2011 |
| Sportech Solutions Limited | Wholesale & retail | 2025 |
| Sporting Analytics Limited | Administrative & support | 2023 |
| Sportsdoc Northeast Limited | Health & social care | 2016 |
| Springer Interiors Ltd | Wholesale & retail | 2020 |
| Springfield Care Home Limited | Health & social care | 2013 |
| Springs Dental Limited | Health & social care | 2017 |
| Spruce Grove Management Company Limited (the) | Households | 1975 |
| Sputnick Limited | Wholesale & retail | 2013 |
| SRB Quality Building Services Ltd | Construction | 2023 |
| SRF Solutions Limited | Other services | 2016 |
| SRG Projects Limited | Professional & scientific | 2025 |
| SRK Spectrum Ltd | Wholesale & retail | 2024 |
| Srms (UK) Limited | Financial services | 2012 |
| SRN Financial Consultancy Ltd | Professional & scientific | 2026 |
| SRP Joinery & Kitchens Ltd | Construction | 2025 |