| SJR Care Limited | Health & social care | 2004 |
| SJW Electrical Limited | Administrative & support | 2003 |
| SKH Prestige Motors Ltd | Wholesale & retail | 2025 |
| SKI 4 Less Limited | Administrative & support | 2002 |
| Skills Training Academy of London Ltd | Construction | 2023 |
| Skin Spark Clinic Ltd | Health & social care | 2017 |
| Skipper International Holdings Limited | Administrative & support | 2026 |
| Skullsdirect Limited | Extraterritorial | 2003 |
| SKW Metals UK Limited | Manufacturing | 1920 |
| Sky Air Travel Limited | Transport & logistics | 1994 |
| Sky Blues Cafe Limited | Hospitality | 2007 |
| Sky Home Solutions Ltd | Real estate | 2018 |
| Sky Travel Experts Limited | Administrative & support | 2026 |
| Skyhigh Consultants Limited | Information & communication | 1995 |
| Skyline Dropship Ltd | Wholesale & retail | 2025 |
| Skyline Healthcare Support Limited | Health & social care | 2023 |
| Skyseer Information Limited | Administrative & support | 2026 |
| Skytouch Limited | Construction | 2001 |
| Skywalk Stays Ltd | Households | 2023 |
| Skyweb Agencies Ltd | Other services | 2002 |
| SL Cuisine Ltd | Hospitality | 2019 |
| Sladja Limited | Professional & scientific | 2002 |
| SLD Venus Digital Ltd | Wholesale & retail | 2025 |
| Sleek HR Limited | Professional & scientific | 2021 |
| Sleep State Limited | Health & social care | 2022 |
| Slick Cluster Limited | Wholesale & retail | 2024 |
| SM Modular Developments Limited | Construction | 2023 |
| SM Precast Consultants Limited | Professional & scientific | 2020 |
| Small Drops | Health & social care | 2020 |
| Smallcombe Limited | Real estate | 1957 |
| Smart Car Trade & Logistics Ltd | Wholesale & retail | 2026 |
| Smart Fleet Ltd | Wholesale & retail | 2018 |
| Smart Saver Store Ltd | Wholesale & retail | 2025 |
| Smarte Limited | Real estate | 2007 |
| Smarter Reach Systems Ltd | Other services | 2026 |
| Smarter Software Solutions Limited | Information & communication | 2017 |
| Smartermax Ltd | Wholesale & retail | 2025 |
| Smash 3 Limited | Hospitality | 2023 |
| Smass Group Limited | Wholesale & retail | 2024 |
| Smatchd Ltd | Information & communication | 2026 |
| Smile Happy Limited | Health & social care | 2007 |
| Smithfield Direct Limited | Wholesale & retail | 2004 |
| Smithson Building Services Limited | Wholesale & retail | 1993 |
| Smoky OUD London Limited | Wholesale & retail | 2025 |
| Smonid Ltd | Health & social care | 2025 |
| SNA Developments Ltd | Real estate | 2023 |
| SNA Enterprises Ltd | Real estate | 2000 |
| Snagtekk Ltd | Construction | 2025 |
| Snakes Lane West Residents Association Limited | Households | 2005 |
| Snakes Meadow Energy Centre Limited | Energy | 2015 |
| Snapshelf Ltd | Wholesale & retail | 2026 |
| Sneakerstoe Limited | Wholesale & retail | 2025 |
| SNH Motors Ltd | Wholesale & retail | 2024 |
| Snowall Limited | Hospitality | 2017 |
| Snowbase Engineering Limited | Real estate | 2002 |
| Snowflake Laundry Limited(The) | Professional & scientific | 1927 |
| SNUG154 Limited | Real estate | 2025 |
| Snugglebuds Ltd | Health & social care | 2025 |
| Sobut Properties Limited | Real estate | 2024 |
| Social Grove (London) Ltd | Professional & scientific | 2024 |
| Social Island Live Ltd | Professional & scientific | 2024 |
| Social Skills Ltd | Health & social care | 2022 |
| Socially Michelle & Co Ltd | Professional & scientific | 2025 |
| Society of North Countrymen (Colchester) Limited(The) | Real estate | 1943 |
| Sodigify Ltd | Information & communication | 2020 |
| Sofiya Residences Ltd | Real estate | 2015 |
| Soft Nest Home Ltd | Wholesale & retail | 2026 |
| Soft Solution IT Ltd | Information & communication | 2025 |
| Soft Thread Co Ltd | Wholesale & retail | 2025 |
| SOFTNOVA24 Ltd | Wholesale & retail | 2025 |
| Softwing (NO.2) Limited | Real estate | 2003 |
| Softwing Limited | Real estate | 2003 |
| Sohal Healthcare Limited | Health & social care | 2004 |
| Soil Investigation (Eastern) Limited | Construction | 2006 |
| Sokhi & Associates Ltd | Professional & scientific | 2000 |
| Solace Protection Limited | Administrative & support | 2020 |
| Solar Free Energy Limited | Professional & scientific | 2005 |
| Solaroid Limited | | 1978 |
| Soleaero Limited | Information & communication | 2002 |
| Solfyr Ltd | Wholesale & retail | 2026 |
| Solidisk Technology Limited | Wholesale & retail | 1982 |
| Solis Commerce Ltd | Wholesale & retail | 2026 |
| Solisnuru Ltd | Information & communication | 2025 |
| Solo Scaffolding Limited | Administrative & support | 2001 |
| Solstice People Development Limited | Professional & scientific | 2004 |
| Soltenda Ltd | Professional & scientific | 2013 |
| Solution 9 Ltd | Wholesale & retail | 2025 |
| Solutions Cleaning and Renovating Limited | Administrative & support | 2004 |
| Solve ID Limited | Information & communication | 2000 |
| Somerbrook Limited | Wholesale & retail | 2001 |
| Soniczero Limited | Information & communication | 2006 |
| Sonning Creatives Ltd | Professional & scientific | 2006 |
| Soods Legal Limited | Professional & scientific | 2003 |
| Soods Limited | Real estate | 2000 |
| Sooraj Limited | Wholesale & retail | 2018 |
| Soteriou & Company Limited | Professional & scientific | 2002 |
| Soulphuel Limited | Manufacturing | 2024 |
| Sound 2 Vision Limited | Information & communication | 2000 |
| Sound Mortgage Options Limited | Administrative & support | 2005 |
| Soundade Limited | Health & social care | 2013 |