| Sims Home Improvements Ltd. | Construction | 2018 |
| Simtax Limited | Professional & scientific | 2014 |
| Simulata Limited | Information & communication | 2016 |
| Sinclair Gore Plastic Surgery Limited | Health & social care | 2014 |
| Sinergia Telecom Ltd | Information & communication | 2013 |
| Sing OUT Ltd | Arts & recreation | 2025 |
| Singh's Stores Ltd | Wholesale & retail | 2019 |
| SIR Systems in Roofing & Property Maintenance Limited | Construction | 2025 |
| Site and Capital Ltd | Professional & scientific | 2026 |
| Siteproof Ltd | Information & communication | 2026 |
| Sitesafe UK Ltd. | Professional & scientific | 1990 |
| Siwek Renovations Ltd | Construction | 2026 |
| Sixty One Integrated Communications Limited | Administrative & support | 2002 |
| SJ Data Visualizations Ltd | Information & communication | 2021 |
| SJC Properties Limited | Real estate | 2002 |
| Sjgc Holdings Limited | Construction | 2002 |
| Skal Restaurants Ltd | Hospitality | 2019 |
| Skalba Limited | Financial services | 2004 |
| Skatterlings of Africa Ltd | Hospitality | 2025 |
| Skeleton MAN Tattoo Ltd | Other services | 2026 |
| Skellerup (UK) Limited | Professional & scientific | 2005 |
| Skelton Tree Services Ltd | Agriculture & fishing | 2025 |
| Skills YOU Need Limited | Information & communication | 2015 |
| SKN & SON 1 Ltd | Wholesale & retail | 2015 |
| Sksw International Ltd | Real estate | 2021 |
| Skyway Care Ltd | Health & social care | 2022 |
| Slater Plastics Limited | Manufacturing | 2009 |
| Slfm Management Ltd | Professional & scientific | 2023 |
| SLJ Automotive Limited | Professional & scientific | 2021 |
| SLK Bathrooms and Maintenance Limited | Construction | 2025 |
| Sm&Ns Ltd | Health & social care | 2025 |
| Smart Horticulture Ltd | Construction | 2019 |
| Smeed Property Ltd | Real estate | 2025 |
| SMG Testing Ltd | Information & communication | 2025 |
| Smith & Butler Limited | Professional & scientific | 2015 |
| Smith & Sons Properties Limited | Administrative & support | 2019 |
| Smith Bros. Metal Recycling Limited | Water & waste | 2006 |
| SMJ Project Services Limited | Professional & scientific | 2010 |
| Smooga Ltd | Construction | 2012 |
| Snedkers Accountancy Services Ltd | Professional & scientific | 2018 |
| Snja Partnership Ltd | Real estate | 2024 |
| SNT Accountancy Ltd | Professional & scientific | 2015 |
| SO Clean Limited | Administrative & support | 2023 |
| Soame Interiors Ltd | Wholesale & retail | 2008 |
| Soame Trading Ltd. | Wholesale & retail | 2012 |
| Sobremesa Ltd | Hospitality | 2017 |
| Soccer Provision International Ltd | Education | 2021 |
| Social Enterprises Evergreen Limited | Financial services | 2015 |
| Softdist Ltd | Wholesale & retail | 2017 |
| Softlink Europe Limited | Information & communication | 1992 |
| Softwash Scaling Ltd | Professional & scientific | 2025 |
| SOH Sand and Gravel Ltd | Wholesale & retail | 2023 |
| Solar Comms Limited | Information & communication | 2015 |
| Solar Limpets Limited | Wholesale & retail | 2004 |
| Solcast Stone Ltd | Construction | 2020 |
| Soleil Property Solution Ltd | Real estate | 2023 |
| Solid Technology Ltd | Manufacturing | 2021 |
| Solmat Properties Limited | Real estate | 2024 |
| Solutions 4 Feet Limited | Wholesale & retail | 2005 |
| Solutions for Service Limited | Other services | 2011 |
| Solwain Limited | Real estate | 1972 |
| Sond Wellbeing Limited | Wholesale & retail | 2014 |
| Sonic Accounting Services Limited | Extraterritorial | 2012 |
| Sopa Ltd | Wholesale & retail | 2024 |
| Sophie OGG Consultancy Ltd | Professional & scientific | 2026 |
| Sorana and Briana Care Ltd | Administrative & support | 2017 |
| Sortedrentals Ltd | Administrative & support | 2025 |
| Sota Gallery (2025) Ltd | Administrative & support | 2025 |
| South & Co Legal Services Ltd | Professional & scientific | 2020 |
| South Arcade Holdings Limited | Financial services | 2025 |
| South Arcade LLP | | 2021 |
| South Park Court Management Limited | Households | 1990 |
| Southbrook Technical Solutions Ltd | Administrative & support | 2026 |
| Space Security Systems Limited | Administrative & support | 2023 |
| Spacial Group Ltd | Arts & recreation | 2025 |
| Spacial Hire Ltd | Arts & recreation | 2025 |
| Spacial Installations Limited | Arts & recreation | 2006 |
| Spacial Storage Ltd | Transport & logistics | 2025 |
| Span Consulting Limited | Professional & scientific | 2016 |
| Spark Ideas International Ltd | Professional & scientific | 2021 |
| Speedier Media Limited | Professional & scientific | 2011 |
| Spencer Bray Holdings Limited | Financial services | 2026 |
| Spice Indira Limited | Hospitality | 2013 |
| Spicy Pumpkin Ltd | Wholesale & retail | 2025 |
| Spicy Robot Ltd | Information & communication | 2023 |
| Spinners Grange (Blockley) Management Company Limited | Households | 2019 |
| Spires Cleaning Ltd | Administrative & support | 2017 |
| Spires Data Solutions Limited | Information & communication | 2014 |
| Spires Mobile Tyres Limited | Wholesale & retail | 2008 |
| Spirit Level Communications Ltd | Professional & scientific | 2015 |
| Sport Operations Limited | Construction | 2022 |
| Sportif Oxford Limited | Wholesale & retail | 2017 |
| Spring Greens Catering Limited | Hospitality | 2019 |
| Spring Grove (Holdings) Limited | Professional & scientific | 2016 |
| Spring Grove House Limited | Agriculture & fishing | 2015 |
| Spring Grove Stables Limited | Agriculture & fishing | 2015 |
| Spring Meadow (Springfields) Management Limited | Households | 2022 |
| Spring Tide Productions Limited | Arts & recreation | 2018 |
| Springfield Place Residents Co. Ltd. | Real estate | 1987 |
| Spruce Works Aviation Ltd | Manufacturing | 2024 |