| Shey & MAS Ltd | Other services | 2018 |
| Shezan Oxford Ltd | Hospitality | 2025 |
| Shiemaa Consulting Services Ltd | Professional & scientific | 2024 |
| Shiftology Ltd | Professional & scientific | 2012 |
| Shimma & Shine Mobile Services Limited | Other services | 2020 |
| Shin OX Limited | Hospitality | 2019 |
| Shining Trade Ltd | Wholesale & retail | 2024 |
| Shiplake Property Investments Ltd | Real estate | 2014 |
| Shipsmart Hub Ltd | Wholesale & retail | 2024 |
| Shiregrove Limited | Construction | 1980 |
| Shirtworks P&E Ltd | Manufacturing | 2024 |
| Shivgems Limited | Wholesale & retail | 2025 |
| Shkun Management Limited | Professional & scientific | 2025 |
| Shoot Aviation (Holdings) Limited | Administrative & support | 2020 |
| Shoot Aviation Limited | Information & communication | 2002 |
| Shoot to Frome Limited | Information & communication | 2021 |
| Shooting Star Retreats Limited | Other services | 2022 |
| Shoprix Ltd | Wholesale & retail | 2024 |
| Shopspot TRD Limited | Wholesale & retail | 2025 |
| Shopwisemarket Limited | Wholesale & retail | 2025 |
| Shotover Communications Limited | Professional & scientific | 2015 |
| Shree Balaji,Oil,Gas,Minerals and Metals Ltd | Manufacturing | 2026 |
| Shrigley Properties Limited | Construction | 2025 |
| Shrimpland Ltd | Wholesale & retail | 2023 |
| Shrimpton Farm Limited | Real estate | 2013 |
| Shrowze Ltd. | Information & communication | 2015 |
| SHS Contracts Ltd | Construction | 2022 |
| Shuffling Wonder Limited | Professional & scientific | 2020 |
| Shunxin Limited | Wholesale & retail | 2015 |
| Si&D (UK) Limited | Wholesale & retail | 2006 |
| SIA Hire Ltd | Administrative & support | 2022 |
| Siad Studio Ltd | Information & communication | 2020 |
| Sibelius Ltd | Professional & scientific | 2009 |
| Sicohn Ltd | Real estate | 2017 |
| Sidds Ltd | Real estate | 2015 |
| Sidra General Limited | Health & social care | 2023 |
| Sierra Medtech Limited | Extraterritorial | 2013 |
| Sierra Oxford Ltd. | Construction | 2024 |
| Sift'D Ltd | Manufacturing | 2025 |
| Sigenex Oxford Ltd | Professional & scientific | 2024 |
| Sigma Z Holdings Limited | Financial services | 2019 |
| Sign Design Oxford Limited | Manufacturing | 2017 |
| Signature Healthcare Communications Ltd | Professional & scientific | 2008 |
| Signet Medical Ltd | Health & social care | 2025 |
| Sikander Grocers Ltd | Hospitality | 2023 |
| Silent Fresh Ltd | Wholesale & retail | 2024 |
| Silhouette Fulfillment Limited | Transport & logistics | 2009 |
| Silicon Life Limited | Information & communication | 2011 |
| Silicon Spires Ltd | Information & communication | 2008 |
| Silk and Associates Limited | Administrative & support | 2014 |
| Silkot (UK) Ltd | Construction | 2018 |
| Silver Construction Ltd | Construction | 2025 |
| Silver Lining Lean Ltd | Administrative & support | 2012 |
| Silver Pacific Limited | Other services | 2001 |
| Silver Sea Insight Limited | Professional & scientific | 2018 |
| Silver Spa Ltd | Other services | 2023 |
| Silverbirch Consultants Ltd | Health & social care | 2025 |
| Silverfore Ltd | Information & communication | 2024 |
| Silverpush Limited | Information & communication | 2023 |
| Silvertone Media Holdings Ltd | Information & communication | 2024 |
| Silvertone Media Ltd | Information & communication | 2024 |
| Silvertree Construction Limited | Real estate | 2019 |
| Simcentric Limited | Information & communication | 2014 |
| Simex Services Limited | Manufacturing | 2017 |
| Simflor Limited | Financial services | 2021 |
| Simha AI Ltd | Professional & scientific | 2024 |
| Simia Investments Limited | Administrative & support | 2013 |
| Simnatox Research Limited | Professional & scientific | 2011 |
| Simon Chatterton Projects Ltd | Arts & recreation | 2009 |
| Simon Horsington and Associates Limited | Professional & scientific | 2010 |
| Simon Raby Anaesthesia Limited | Health & social care | 2018 |
| Simon Saunders Limited | Manufacturing | 2003 |
| Simple Financials Limited | Real estate | 2021 |
| Simple Productions Oxford Ltd | Arts & recreation | 2018 |
| Simple Promotions Limited | Hospitality | 2014 |
| Simplicity Communications Limited | Information & communication | 2005 |
| Simplifihr Limited | Professional & scientific | 2024 |
| Simply Fertility Ltd | Health & social care | 2013 |
| Simply Hair and Beauty (Kennington) Ltd | Other services | 2022 |
| Simply Prime Ltd | Wholesale & retail | 2025 |
| Simply PUT Accounting Limited | Professional & scientific | 2024 |
| Simply Study Abroad Ltd | Information & communication | 1997 |
| Simpsons Way Management Company Limited | Households | 2011 |
| Sinal House Services Limited | Information & communication | 2025 |
| Sindall & Baker Exhibitions Limited | Arts & recreation | 1970 |
| Singh's OFF Licence Ltd | Wholesale & retail | 2019 |
| Singula BIO Ltd | Health & social care | 2020 |
| SIR William Osler Programme for Innovation in Medicine CIC | Professional & scientific | 2019 |
| Sirail Limited | Extraterritorial | 2017 |
| Sirc Limited | Professional & scientific | 2014 |
| Siriami Ltd | Professional & scientific | 2003 |
| Siris Hill Ltd | Arts & recreation | 2023 |
| Sirius Partners Ltd. | Professional & scientific | 2014 |
| Sirv Limited | Information & communication | 2007 |
| Sisa Creative Ltd | Information & communication | 2021 |
| Sisters Edge Limited | Other services | 2010 |
| Sitaarah Limited | Manufacturing | 2019 |
| Site Team App Ltd | Information & communication | 2025 |
| Site Team Services Ltd | Construction | 2010 |
| Sitleft Ltd | Education | 2017 |