| SLJ Premier Properties Ltd | Real estate | 2025 |
| SLM Property Lets Ltd | Real estate | 2019 |
| SLS Joinery Services Ltd | Construction | 2023 |
| Sm-Antler Ltd | Wholesale & retail | 2024 |
| Smallys Mobile Detailing Ltd | Wholesale & retail | 2025 |
| Smart Homes N.E Ltd | Households | 2020 |
| Smart IOT Solutions Limited | Information & communication | 2019 |
| Smart Property Consultancy Ltd | Professional & scientific | 2026 |
| Smarten UP Podiatry and Training Ltd | Health & social care | 2026 |
| Smartifier Ltd | Information & communication | 2022 |
| Smartpeoplesolutions Ltd | Administrative & support | 2021 |
| Smeworsk Ltd | Wholesale & retail | 2025 |
| SMF Legal Services Limited | Professional & scientific | 2025 |
| SMI House Limited | Real estate | 2020 |
| Smidatech Ltd | Financial services | 2025 |
| Smile Inc Ltd | Health & social care | 2012 |
| Smit's Pet Services Limited | Arts & recreation | 2023 |
| Smith & Thomas Injury Rehabilitation Centre Ltd | Health & social care | 2016 |
| Smith Construction Management Ltd | Professional & scientific | 2026 |
| Smith EHV Ltd | Professional & scientific | 2026 |
| Smithhawk Investments Ltd | Real estate | 2024 |
| SMM Roofing Ltd | Construction | 2026 |
| Smooth Delivery Ltd | Transport & logistics | 2024 |
| SNB Project Management Ltd | Professional & scientific | 2010 |
| Snooker Club Ltd | Arts & recreation | 2025 |
| Snzr Limited | Construction | 2017 |
| Social & Care Recruitment Ltd | Administrative & support | 2021 |
| Social Allies Limited | Professional & scientific | 2019 |
| Social Aspect Limited | Manufacturing | 2017 |
| Softpower Limited | Professional & scientific | 2013 |
| Softwareqasolutions Ltd | Professional & scientific | 2018 |
| SOG Electrical Access Ltd | Construction | 2022 |
| SOG Holdings Limited | Wholesale & retail | 2023 |
| Sohel Abdullah AL Yusuf Trading and Constracting Ltd | Construction | 2025 |
| Soigne Bakery Ltd | Wholesale & retail | 2024 |
| Sokses Jewellery Limited | Manufacturing | 2014 |
| Solar Style Distributions Ltd | Construction | 2019 |
| Soleni Systems Ltd | Agriculture & fishing | 2026 |
| Solid Bond Solutions Limited | Construction | 2015 |
| Solid Software Consulting Limited | Information & communication | 2013 |
| Solida Limited | Real estate | 2024 |
| Solmek Limited | Professional & scientific | 2000 |
| Somerford Property Services Limited | Real estate | 2021 |
| Somerville Court Residents' Association Limited | Households | 1990 |
| Sophie Pearson Casting UK Ltd | Administrative & support | 2025 |
| Sorcha's Artisan Bakehouse Ltd | Manufacturing | 2024 |
| Sortology Limited | Water & waste | 2011 |
| Soteria (NE) Limited | Professional & scientific | 2026 |
| Sound Training for Reading Ltd | Information & communication | 2009 |
| South Durham Construction Ltd | Construction | 2026 |
| South Durham Group Ltd | Construction | 2022 |
| South Durham Removals Ltd | Transport & logistics | 2025 |
| South Grange Medical Services Ltd | Health & social care | 2013 |
| South Ormsby Resources Limited | Information & communication | 2016 |
| Southern Asset Management Limited | Manufacturing | 2022 |
| Southern Building & Shopfitting Limited | Construction | 2013 |
| Sovietania Limited | Manufacturing | 2017 |
| Sowerby Removals & Transport Ltd | Transport & logistics | 2025 |
| Sowft Limited | Information & communication | 2026 |
| Sowing Seeds Ministries | Health & social care | 2006 |
| SP Electrical Contractors Limited | Construction | 2007 |
| Spark Aspirations Tees Valley Ltd | Education | 2019 |
| Spark Education Trust | Education | 2016 |
| Spark Succession Ltd | Hospitality | 2017 |
| Sparkles & Graham Property Group Ltd | Real estate | 2025 |
| Sparkwood Limited | Professional & scientific | 1981 |
| Sparky Copy Ltd | Professional & scientific | 2019 |
| Sparkyninja Ltd | Education | 2019 |
| Sparton Services Limited | Construction | 2020 |
| Spazy Welding Limited | Manufacturing | 2025 |
| Speargroup Limited | Manufacturing | 2009 |
| Specialist Shale Removal Ltd | Construction | 2018 |
| Specwise Design Ltd | Professional & scientific | 2025 |
| Spencer Bellamy Holdings Ltd | Financial services | 2023 |
| Spencerzill UK Ltd | Information & communication | 2022 |
| Spencley Design & Inspection Services Limited | Professional & scientific | 2025 |
| Spensley Family Office Ltd | Real estate | 2024 |
| SPH Structures Limited | Construction | 2018 |
| Sphere IT Solutions Ltd | Information & communication | 2023 |
| Spice Yarm Limited | Hospitality | 2024 |
| Spicer Finch Limited | Administrative & support | 2010 |
| Spicy Panda Limited | Hospitality | 2025 |
| Spineology Ltd | Health & social care | 2017 |
| SPIRIT12 Ltd | Transport & logistics | 2026 |
| SPM Retail Limited | Wholesale & retail | 2020 |
| Spoton Servicing Limited | Wholesale & retail | 2019 |
| Sprayworx North East Ltd | Wholesale & retail | 2024 |
| Sprout & Bloom Preschools Limited | Education | 2025 |
| Spruce Technology Limited | Wholesale & retail | 2025 |
| Spud E Licious Ltd | Hospitality | 2025 |
| Squadron Court (Thornaby) Management Company Limited | Real estate | 2008 |
| SR Advanced Healthcare Ltd | Administrative & support | 2025 |
| SR Offshore and Marine Ltd | Professional & scientific | 2013 |
| SR Psychotherapies Ltd | Health & social care | 2019 |
| SR Retailing Ltd | Wholesale & retail | 2023 |
| SRC: Lifting Compliance Services Limited | Construction | 2022 |
| SRH (Onsite) Limited | Transport & logistics | 2011 |
| SRS Rigging Limited | Construction | 2016 |
| SS Kang Logistics Ltd | Transport & logistics | 2025 |
| SS Seed Co. Limited | Wholesale & retail | 2010 |