| Sitryx Therapeutics Limited | Professional & scientific | 2016 |
| SIX Mill Consulting Limited | Professional & scientific | 2017 |
| Sixstones Ltd | Construction | 2010 |
| Sixth EYE Ltd | Information & communication | 2026 |
| Sixth Wave Ltd | Professional & scientific | 2023 |
| Size Matters Products Limited | Wholesale & retail | 2020 |
| SJC Carpentry Services Ltd | Construction | 2022 |
| SJF Consulting Limited | Professional & scientific | 2012 |
| SJM Industrial Sparks Ltd | Construction | 2024 |
| SJM Motor Repairs Ltd | Wholesale & retail | 2009 |
| Sjmoore Heating & GAS Ltd | Construction | 2008 |
| Sjotta Limited | Real estate | 2017 |
| SJP Projects Limited | Construction | 2005 |
| SK & HK Ltd | Health & social care | 2022 |
| SK Dream Properties Ltd | Real estate | 2026 |
| SK Dream Properties Services Ltd | Real estate | 2026 |
| Skelly Holdings Ltd | Financial services | 2025 |
| Skepi Ltd | Construction | 2019 |
| Sketch N CUT Barbers Ltd | Other services | 2024 |
| Skibars Innovative UK Ltd | Wholesale & retail | 2026 |
| Skillpedia Ltd | Education | 2016 |
| Skills Consultancy Management Limited | Water & waste | 2022 |
| Skmo Logistics Ltd | Transport & logistics | 2024 |
| Skoglund Enterprises Ltd | Professional & scientific | 2015 |
| SKP Tax & Accounting Services Ltd | Professional & scientific | 2020 |
| Skullvikings Ltd | Wholesale & retail | 2018 |
| SKW Ltd | Professional & scientific | 2024 |
| Skwky Ltd | Information & communication | 2026 |
| Sky High Logistics Limited | Transport & logistics | 2026 |
| Sky TEK Roofing Ltd | Construction | 2024 |
| Skycall Limited | Professional & scientific | 2000 |
| Skyford Limited | Hospitality | 2023 |
| Skygoo Traders Limited | Wholesale & retail | 2024 |
| Skylark Consulting Ltd | Information & communication | 2020 |
| Skyline DC Energy Ltd | Construction | 2023 |
| Skyline DC Group Ltd | Construction | 2023 |
| Skyline DC Ltd | Construction | 2023 |
| Skyline Education Consulting Co., Ltd | Professional & scientific | 2024 |
| Skyspace Global Limited | Real estate | 2024 |
| Skytek Technology Limited | Information & communication | 2017 |
| Skyvora Tours & Travel Ltd | Administrative & support | 2025 |
| Skyward Digital Reach Ltd | Wholesale & retail | 2023 |
| Skyways Aerospace Limited | Manufacturing | 2022 |
| SL & Sons Limited | Real estate | 2023 |
| Slater Labs Limited | Information & communication | 2025 |
| SLC Geomatic Solutions Ltd. | Professional & scientific | 2001 |
| Sleep & Stay Oxford Limited | Hospitality | 2018 |
| Sleep Asylum Ltd | Health & social care | 2021 |
| SLG 2017 Limited | Construction | 2017 |
| Slice Hospitality Ltd | Arts & recreation | 2025 |
| Slieveroe Aero Limited | Professional & scientific | 2020 |
| SLK Media Marketing Ltd | Professional & scientific | 2025 |
| Sloan & Partners Consultancy Ltd | Professional & scientific | 2010 |
| Sloane Consultancy Oxford Limited | Public administration | 2017 |
| Sloping Acre Development Co Ltd | Construction | 2021 |
| Slough House Limited | Arts & recreation | 2018 |
| SM Busy BEE Limited | Wholesale & retail | 2016 |
| Small World Nursery Limited | Education | 1994 |
| Smart Cutie Ltd | Wholesale & retail | 2025 |
| Smart Energy Generations Ltd | Construction | 2024 |
| Smart Home Lettings Limited | Real estate | 2021 |
| Smart Web Digital Ltd | Other services | 2023 |
| Smarter Coaching Ltd | Professional & scientific | 2019 |
| Smartprotein Designs Ltd | Professional & scientific | 2026 |
| Smash Three (Oxford) Limited | Hospitality | 2019 |
| Smehmood Ltd | Wholesale & retail | 2025 |
| Smets & Morris Ltd | Professional & scientific | 2022 |
| Smiles Space Ltd | Construction | 2021 |
| Smiley Happy Monkeys Ltd. | Health & social care | 2012 |
| Smiley Property Management Company Limited | Households | 2007 |
| Smith & Guinan Limited | Financial services | 2017 |
| Smith & LOW Limited | Wholesale & retail | 2002 |
| Smith & Sons (Bletchington) Limited | Agriculture & fishing | 1947 |
| Smith Mathematical Consultancy Limited | Education | 2014 |
| Smith's Limestone Limited | Mining & quarrying | 1973 |
| Smithfield Market Limited | Extraterritorial | 2007 |
| Smoke With Sawyer Ltd | Hospitality | 2025 |
| Smoon Property Maintenance Ltd | Construction | 2024 |
| Smouse & Marchand Limited | Wholesale & retail | 2014 |
| Smpropainters Limited | Construction | 2022 |
| Smudger Enterprises LLP | | 2010 |
| Smug RUG Ltd | Extraterritorial | 2020 |
| SMY Electrical Limited | Construction | 1998 |
| Snaith Consulting Limited | Professional & scientific | 2014 |
| Snakesong Ltd | Administrative & support | 2019 |
| Snap on Veneers Ltd | Wholesale & retail | 2025 |
| Snapdragon Investment Services Limited | Financial services | 2017 |
| Snapdragon Publishing (Oxford) Ltd | Information & communication | 2014 |
| Sniper Productions Ltd | Information & communication | 2017 |
| Snowflake Books Ltd | Information & communication | 2010 |
| Snowfox Discovery Ltd | Mining & quarrying | 2023 |
| SNS Oxford Ltd | Hospitality | 2024 |
| SO Bangkok Group Ltd | Hospitality | 2025 |
| SO Clean & SO Fresh Ltd | Administrative & support | 2025 |
| Sobell House Hospice Charity Limited | Wholesale & retail | 2006 |
| Sobell Lottery Ltd | Arts & recreation | 1999 |
| Socatots Limited | Arts & recreation | 2003 |
| Socatots Oxfordshire LLP | | 2018 |
| Social Care Works Limited | Professional & scientific | 2017 |
| Social Justice and Human Rights Centre Limited | Real estate | 2011 |