| Skillsmile Consulting Ltd | Information & communication | 2018 |
| Skillsmile Makes Ltd | Professional & scientific | 2025 |
| Skinovate Limited | Other services | 2004 |
| Skirts 'R' US Limited | Administrative & support | 2010 |
| SKP Hotels Ltd | Real estate | 2018 |
| Skyhook Projects Ltd | Professional & scientific | 2018 |
| Sleep & Health Clinic Ltd | Health & social care | 2014 |
| Sleep and Health Clinic App Limited | Information & communication | 2020 |
| Sleep and Health Global Limited | Health & social care | 2005 |
| Sleepwell Property Management Limited | Real estate | 2026 |
| Slipstream Technologies Limited | Information & communication | 2019 |
| Sloane Square Chiropractors Limited | Health & social care | 2010 |
| Smart 21 Ltd | Other services | 2010 |
| Smart Meadows Farm Ltd | Administrative & support | 2019 |
| Smartfox Consulting Ltd. | Administrative & support | 2014 |
| Smartmotion Systems Ltd | Professional & scientific | 2025 |
| Smile KT1 Ltd | Health & social care | 2019 |
| Smile Radiance Limited | Health & social care | 1998 |
| Smile Sublime Ltd | Health & social care | 2017 |
| Smilealot Limited | Health & social care | 2025 |
| SML Properties Limited | Real estate | 2002 |
| SMM Marketing Limited | Professional & scientific | 2011 |
| Smsuk Limited | Information & communication | 2014 |
| SNA Life Ltd | Administrative & support | 2019 |
| SNA Property Limited | Real estate | 2020 |
| Snaresbrook News Limited | Wholesale & retail | 2020 |
| Snekker Build Limited | Construction | 2025 |
| Snif Limited | Wholesale & retail | 2025 |
| SNJ Link Holdings Limited | Financial services | 2023 |
| SNK Properties (London) Limited | Real estate | 2013 |
| Soar Investments Ltd | Wholesale & retail | 2001 |
| Social SIP Limited | Hospitality | 2026 |
| Social Status Ltd | Professional & scientific | 2020 |
| Software Crafts Limited | Information & communication | 1998 |
| Software Quality Limited | Information & communication | 2008 |
| Software Signals Limited | Administrative & support | 2013 |
| Software Testing Services Ltd | Information & communication | 2016 |
| Solo Womenswear Ltd | Wholesale & retail | 2009 |
| SOLUTION2ALL Ltd | Administrative & support | 2018 |
| Somewhere Limited | Professional & scientific | 2009 |
| Sonawala Estates Ltd | Real estate | 2023 |
| Soni International Ltd | Wholesale & retail | 2024 |
| Sontania Properties Limited | Real estate | 2002 |
| Sonya Capital Developments Ltd | Construction | 2025 |
| Sonya Capital Group Ltd | Real estate | 2025 |
| Sophie Grace Interior Design Limited | Professional & scientific | 2023 |
| Sort My Shop Limited | Extraterritorial | 2026 |
| Soul Coffee House (Central) Limited | Hospitality | 2015 |
| Soul Coffee House (East) Limited | Hospitality | 2015 |
| Soul Coffee House (London) Limited | Hospitality | 2016 |
| Soul Coffee House (South) Limited | Hospitality | 2015 |
| Soul Coffee House (West) Limited | Hospitality | 2015 |
| Soul Coffee House Limited | Professional & scientific | 2015 |
| Sound Bookings Limited | Arts & recreation | 2008 |
| Sourina Ltd | Other services | 2015 |
| South Gardens Management Company Limited | Real estate | 1983 |
| South West London Construction Ltd | Construction | 2015 |
| SP Holdco Ltd | Real estate | 2025 |
| Space Made Ltd | Construction | 2010 |
| Sparkle Work Developers Ltd | Construction | 2025 |
| Sparsh Technologies Limited | Information & communication | 2006 |
| Spearbond Limited | Real estate | 2011 |
| Spearcroft Limited | Real estate | 2013 |
| Specialist Plumbing Solutions Ltd | Construction | 2012 |
| Spectrum Biometrics Limited | Information & communication | 2023 |
| Spectrum Sign Writing Limited | Other services | 2013 |
| Spiracheck Limited | Professional & scientific | 2016 |
| Spiral Computing Limited | Information & communication | 2002 |
| Sport First Education and Mentoring Ltd | Education | 2024 |
| Sports Orthopaedics Research Foundation | Health & social care | 2010 |
| Sports Orthopaedics UK Limited | Health & social care | 2005 |
| Spotlight Properties Limited | Real estate | 2014 |
| Spring AD Consultancy Limited | Other services | 2018 |
| Spring Valley Care Services Ltd | Public administration | 2018 |
| Springwell Property Management Ltd | Real estate | 2017 |
| SPT Property Management Limited | Real estate | 2017 |
| SR & DR Khiroya LLP | | 2024 |
| SR GP Services Ltd | Other services | 2014 |
| Sran Goods Ltd | Wholesale & retail | 2022 |
| SRG Estates Limited | Real estate | 2022 |
| SRI Viraj Solutions Ltd | Information & communication | 2017 |
| SRK Project Consultancy Ltd | Real estate | 2022 |
| Srkr Accountants Ltd | Households | 2019 |
| Srkr Associates Limited | Professional & scientific | 2010 |
| Srsly Ltd | Hospitality | 2019 |
| SS Aesthetics Limited | Health & social care | 2022 |
| SS Asset Management Limited | Real estate | 2014 |
| SS Equity Ltd | Real estate | 2024 |
| Ss&A Consulting Limited | Professional & scientific | 2018 |
| Ssm(London) Ltd | Hospitality | 2025 |
| SSO and Associates Limited | Real estate | 2016 |
| SSP Hotels Ltd | Real estate | 2018 |
| Sstuk Limited | Manufacturing | 2024 |
| ST Consultants Limited | Administrative & support | 2017 |
| ST George Enterprises Ltd | Information & communication | 2009 |
| ST Helen's Enterprises Limited | Arts & recreation | 1993 |
| ST James Assets Ltd | Real estate | 2024 |
| ST Matthews Court Limited | Real estate | 2019 |
| Stabasum Ltd | Health & social care | 2021 |
| Stak Property Ltd | Real estate | 2025 |