| Simmons & Schmid Limited | Information & communication | 2020 |
| Simon Carey Consultancy Limited | Professional & scientific | 2025 |
| Simonsberg Investment Ltd | Professional & scientific | 2022 |
| Simple Structures Ltd | Manufacturing | 2015 |
| Simplicity Holdings Limited | Real estate | 2022 |
| Simply Convenience Ltd | Wholesale & retail | 2025 |
| Simply Local Retail Ltd | Wholesale & retail | 2024 |
| Simply Lofts and Extensions Ltd | Construction | 2014 |
| Simpson Travel Bidco Limited | Financial services | 2024 |
| Simpson Travel Topco Limited | Financial services | 2024 |
| Simran Dhariwal Ltd | Information & communication | 2026 |
| Sinet Systems Limited | Information & communication | 2000 |
| Sing Education Limited | Education | 2014 |
| Singing Holidays Limited | Administrative & support | 2018 |
| Sino-Brit Technology and Culture Development Company Ltd | Wholesale & retail | 2012 |
| SIP Coffee Ltd | Hospitality | 2019 |
| Sipnsnack Limited | Hospitality | 2012 |
| Sitepointers Limited | Real estate | 1973 |
| Siva Siva Limited | Wholesale & retail | 2017 |
| Sivaalgos Ltd | Professional & scientific | 2023 |
| SJ Productions Ltd | Professional & scientific | 2022 |
| SJ Weston Engineering Limited | Administrative & support | 2007 |
| Sjdquin Ltd | Information & communication | 2014 |
| Sjelements Ltd | Professional & scientific | 2025 |
| SJL Ventures Ltd | Real estate | 2024 |
| SK Medical Services (NE) Limited | Health & social care | 2015 |
| Skayed Limited | Information & communication | 2023 |
| SKI Line Limited | Administrative & support | 1995 |
| SKI Safari Limited | Administrative & support | 1996 |
| SKI Safari Mountain Tracks Ltd | Administrative & support | 2026 |
| SKI Solutions (Transport) Limited | Transport & logistics | 2012 |
| SKI Solutions Holdings Limited | Financial services | 2010 |
| SKI Solutions Limited | Administrative & support | 1985 |
| Skillcore Ltd | Real estate | 2025 |
| Skilljumper Limited | Information & communication | 2024 |
| Skillnet Solutions Private Limited | Information & communication | 2010 |
| Skills Insight Limited | Administrative & support | 2010 |
| Skin Lounge Limited | Other services | 2012 |
| Skin Revive London Ltd | Health & social care | 2021 |
| Skin Studio DR Shivani Ltd | Health & social care | 2023 |
| SKS (London City) Ltd | Professional & scientific | 2018 |
| Slayed by Shay Ltd. | Other services | 2019 |
| SLF Events Ltd | Administrative & support | 2025 |
| Slide Cloud Ltd | Wholesale & retail | 2025 |
| Slim Chance Production Ltd | Information & communication | 2024 |
| SLK Advisory Limited | Professional & scientific | 2015 |
| Sloa Ltd | Households | 2016 |
| Sm&K Properties Ltd | Real estate | 2020 |
| SM2 Heights Holdings Ltd | Construction | 2025 |
| SM2HEIGHTS Limited | Construction | 2024 |
| Small Steps SFP | Education | 2013 |
| Smaller Biggie Productions Ltd | Real estate | 2018 |
| Smallways Ltd | Hospitality | 2015 |
| Smart Co Consulting Limited | Information & communication | 2006 |
| Smart Design Electrical Ltd | Construction | 2023 |
| Smart Integrated Property Ltd | Construction | 2016 |
| Smart Property Care Ltd | Professional & scientific | 2015 |
| Smartport Europe Ltd | Information & communication | 2018 |
| Smash Republic Ltd | Wholesale & retail | 2023 |
| SMC Abbey Road Limited | Construction | 2024 |
| Smile Events Live Limited | Hospitality | 2025 |
| Smokersdlite Limited | Wholesale & retail | 2013 |
| Smooth Event Management Limited | Administrative & support | 2009 |
| Snabbit Limited | Real estate | 2022 |
| Snap Telly Ltd | Information & communication | 2025 |
| Snorkel Venture Limited | Administrative & support | 2015 |
| SO TM Services Ltd | Construction | 2018 |
| Soane Restorations Limited | Professional & scientific | 2002 |
| Social Pedagogy Professional Association | Professional & scientific | 2017 |
| Socialodge Ltd | Construction | 2025 |
| Soft Trading Limited | Wholesale & retail | 2013 |
| Softech 2000 Limited | Information & communication | 2004 |
| Softexa Limited | Information & communication | 2026 |
| Softservegelato Ltd | Wholesale & retail | 2024 |
| Software (Europe) Limited | Information & communication | 2011 |
| Sol*Aire Heating Products Limited | Manufacturing | 2009 |
| Solargrid TS Limited | Administrative & support | 2026 |
| Solatherm Ltd | Administrative & support | 2011 |
| Sole Inc Limited | Other services | 2014 |
| Soliden Investments Limited | Real estate | 2024 |
| Soloway Software Limited | Information & communication | 2021 |
| SOM Tyas Ltd | Hospitality | 2026 |
| Somerset Pharmaceuticals Limited | Wholesale & retail | 2020 |
| Sometime After Midnight Ltd | Information & communication | 2024 |
| Somos Consulting Limited | Professional & scientific | 2022 |
| Songbird Press Limited | Information & communication | 2024 |
| Sophie Jones LDN Ltd | Information & communication | 2018 |
| Sophie Pettengale Ltd | Professional & scientific | 2018 |
| Sophie Southmayd Consulting Ltd | Information & communication | 2019 |
| Sorrento Education Ltd | Education | 2025 |
| Sough Enterprises Ltd | Agriculture & fishing | 2026 |
| Soul Content Ltd | Information & communication | 2012 |
| Sound Intelligence Limited | Extraterritorial | 2005 |
| Sound Simpatico Limited | Other services | 2006 |
| Sound State Ltd | Information & communication | 2013 |
| South Lodge Owners Assn. Limited | Households | 2016 |
| South London Couriers Ltd | Transport & logistics | 2020 |
| South London Trailer Centre Ltd | Other services | 1998 |
| Southall Aviation Ltd | Administrative & support | 2010 |
| Southall Enterprise Limited | Transport & logistics | 2013 |