| Shreevilla Properties Limited | Real estate | 2020 |
| Shukla Estate PVT Ltd | Real estate | 2025 |
| Shun YAN Holdings Limited | Real estate | 2024 |
| Side Quest Services Ltd | Information & communication | 2026 |
| Sierra Lima Consulting Limited | Professional & scientific | 2025 |
| Sierra One Services Ltd | Administrative & support | 2025 |
| SIG Property Investments Ltd | Real estate | 2025 |
| Sigmoid Solutions Limited | Manufacturing | 2023 |
| Signamics Limited | Information & communication | 2009 |
| Siixteen Ltd | Hospitality | 2019 |
| Sildown Limited | Hospitality | 2001 |
| Silent Disco UK Limited | Administrative & support | 2011 |
| Silk Routes Logistics Ltd | Wholesale & retail | 2024 |
| Silky Brows Limited | Other services | 2014 |
| Silver Home Solutions Ltd | Construction | 2026 |
| Silver Penny Consulting Ltd | Information & communication | 2024 |
| Silverline Electrical Contractors Limited | Construction | 2018 |
| Silveroak Private Ltd | Real estate | 2022 |
| Silwood of Bracknell DRY Cleaning Limited | Other services | 2020 |
| Simon 2000 Limited | Manufacturing | 2000 |
| Simple Aesthetics Ltd | Professional & scientific | 2021 |
| Simple Fintec Limited | Information & communication | 2025 |
| Simply Beauty Studio Ltd | Other services | 2025 |
| Simply Blinds (UK) Limited | Wholesale & retail | 2014 |
| Simply Safe for Contractors Ltd | Professional & scientific | 2025 |
| Simply SEW Crafty Ltd | Wholesale & retail | 2021 |
| SINGH13 Ltd | Wholesale & retail | 2024 |
| Sirenlight Consulting and Trading Ltd | Professional & scientific | 2009 |
| Sitacat Ltd | Transport & logistics | 2013 |
| Siwa Hair & Cosmetics Ltd | Wholesale & retail | 2020 |
| Sixpence Design Limited | Manufacturing | 2013 |
| SJ Charlton Services Limited | Professional & scientific | 2022 |
| SJ Forbes Ltd | Other services | 2016 |
| SJS Vehicle Services Ltd | Wholesale & retail | 2026 |
| SJW Plumbing & Heating Ltd | Construction | 2021 |
| SK Nutriments Ltd | Wholesale & retail | 2024 |
| SKD Accounting Limited | Professional & scientific | 2016 |
| Skillmine Ltd | Information & communication | 2026 |
| Skillwise Investments Limited | Wholesale & retail | 2015 |
| Skillz-School Ltd | Education | 2025 |
| Skin & Soul Collective Ltd | Other services | 2025 |
| Skintelligent Research LAB Ltd | Wholesale & retail | 2024 |
| Skitech Systems Ltd | Manufacturing | 1985 |
| Skream Limited | Wholesale & retail | 2002 |
| Skrybe Ltd | Information & communication | 2022 |
| SKS Window Cleaning Ltd | Administrative & support | 2008 |
| Skye Business Solutions Limited | Professional & scientific | 2017 |
| Skyelarke Technologies Limited | Information & communication | 2022 |
| SKYL4RK UK Ltd | Financial services | 2022 |
| Skylinks Consulting Ltd | Information & communication | 2016 |
| Slade Cloud Consulting Ltd | Information & communication | 2026 |
| Slam IT Holdings Limited | Information & communication | 2016 |
| Slaviksm Furniture Ltd | Administrative & support | 2017 |
| Sleep Well With Hannah Ltd | Health & social care | 2022 |
| Slipstream Personal Training Limited | Other services | 2007 |
| SLK Estates Limited | Real estate | 2021 |
| Slough and Windsor Railway Society | Other services | 2009 |
| Slough House Farms Ltd | Agriculture & fishing | 2023 |
| SM Building and Roofing Specialist Ltd | Construction | 2025 |
| Smart Car Wash - Smart Robot Ltd | Construction | 2023 |
| Smart Electronic Technologies Ltd | Wholesale & retail | 2002 |
| Smart Fiber Ltd | Construction | 2022 |
| Smart FT Limited | Construction | 2010 |
| Smart H & S Limited | Wholesale & retail | 2009 |
| Smart Key Management Ltd | Real estate | 2025 |
| Smart Process Consulting Ltd | Administrative & support | 2017 |
| Smart Renovate Ltd | Construction | 2017 |
| Smart Salons UK Ltd | Other services | 2019 |
| Smart Signs Group Ltd | Manufacturing | 2011 |
| Smart Stop Ltd | Wholesale & retail | 2021 |
| Smart Wash Bracknell Ltd | Other services | 2021 |
| Smartech Integration Ltd | Information & communication | 2023 |
| Smartek Construction Ltd | Construction | 2025 |
| Smarter-Home Services Limited | Other services | 2025 |
| Smartomz Ltd | Wholesale & retail | 2016 |
| Smashlogic Solutions Limited | Professional & scientific | 2019 |
| SMC Design Creative Limited | Professional & scientific | 2014 |
| SMC Gardening and Landscaping Services Limited | Extraterritorial | 2022 |
| Smdattani Ltd | Real estate | 2024 |
| SME Link Limited | Information & communication | 1998 |
| Smith Slade Taylor Limited | Real estate | 2021 |
| Smithlab Ltd | Information & communication | 2026 |
| Smoothie DOC Ltd | Manufacturing | 2023 |
| SMT Painting and Decorating Ltd | Construction | 2024 |
| SN Property Management (Binfield) Ltd | Real estate | 2021 |
| Sndtransport Ltd | Transport & logistics | 2020 |
| Snow Trippin Limited | Hospitality | 2014 |
| Snowflake Polo Ltd | Agriculture & fishing | 2025 |
| SNS Security Ltd | Administrative & support | 2015 |
| Sntr Limited | Wholesale & retail | 2024 |
| Snugg Developments Limited | Construction | 2021 |
| SO Integrations Ltd | Wholesale & retail | 2013 |
| SO4 Offshore Limited | Professional & scientific | 2009 |
| Social Pro-Grammers Limited | Information & communication | 2017 |
| Socialhood Marketing Ltd | Professional & scientific | 2022 |
| Sofia 1989 Ltd | Extraterritorial | 2026 |
| Softcow Software Limited | Extraterritorial | 2016 |
| Software AG (UK) Limited | Information & communication | 1977 |
| SOL Property Solutions Ltd | Construction | 2022 |
| Solarsoft Acquisition Limited | Financial services | 2008 |