| Sigered Developments Limited | Construction | 2018 |
| Sigma Racing Limited | Other services | 2011 |
| Signature Chauffeuring (Essex) Limited | Other services | 2019 |
| Signexcel Limited | Manufacturing | 2001 |
| Sili-Con Rendering Ltd | Construction | 2021 |
| Siliconyte Ltd | Information & communication | 2025 |
| Silk Mill (East Hanney) Management Company Limited | Households | 2019 |
| Silk Property Portfolio Ltd | Real estate | 2018 |
| Silkwood Gate (Wakefield) Management Company Limited | Households | 2014 |
| Silver Light Holdings Ltd | Real estate | 2020 |
| Silver Slate Childcare Limited | Education | 2025 |
| Silver Strike Ltd | Wholesale & retail | 2025 |
| Silvercent Consulting and Accountancy Services Limited | Professional & scientific | 2013 |
| Silverhawk Consultancy Services Ltd | Professional & scientific | 2017 |
| Silverstonebks Limited | Professional & scientific | 2018 |
| Simon Carter Interiors Limited | Construction | 2025 |
| Simon Houlding Upholstery Limited | Other services | 2013 |
| Simon Hughes Electrical Services Limited | Energy | 2015 |
| Simply Blues Restaurants Limited | Hospitality | 1996 |
| Simply Coffeenated Ltd | Hospitality | 2025 |
| Simplyprops Ltd | Real estate | 2026 |
| Simster Limited | Professional & scientific | 2020 |
| Sing IT Events and Entertainment Limited | Administrative & support | 2023 |
| Sing IT Events Limited | Arts & recreation | 2021 |
| Sini Management Solutions Ltd | Professional & scientific | 2022 |
| Site Protection UK Ltd | Construction | 2023 |
| Site-Street Limited | Information & communication | 2007 |
| Sjks Asset Management Limited | Real estate | 2024 |
| SJS Motors Limited | Wholesale & retail | 2024 |
| SK Cafe & Cocktails Ltd | Hospitality | 2024 |
| SK Hairstyling Limited | Other services | 2025 |
| SKA Optical Limited | Wholesale & retail | 2026 |
| Skarchitects Limited | Professional & scientific | 2008 |
| Skillplus Tuition Ltd | Education | 2022 |
| Skin by Rhianne Ltd | Other services | 2024 |
| Skinplex Aesthetics Ltd | Other services | 2025 |
| Sky Campion Limited | Hospitality | 2026 |
| SKY7 Trans Ltd | Transport & logistics | 2017 |
| Skylite Express (UK) Limited | Administrative & support | 2012 |
| Skyton Short Term Stays Ltd | Real estate | 2025 |
| SL Management and Consultancy Ltd | Financial services | 2024 |
| Slds Property Management Ltd | Real estate | 2026 |
| Sleek Sealants Ltd | Construction | 2026 |
| SLG Electrical Ltd | Construction | 2012 |
| Slim Ricks Ltd | Wholesale & retail | 2021 |
| SLK One Limited | Real estate | 2002 |
| SLM Star Limited | Construction | 2016 |
| Sloane Street Holdings Limited | Extraterritorial | 2005 |
| Sloane Street Nominees Limited | Extraterritorial | 2004 |
| Slowbond Properties Limited | Real estate | 2006 |
| SM & MA Limited | Hospitality | 2019 |
| Smart & Simple Solutions Ltd | Construction | 2012 |
| Smart Assist Ltd | Administrative & support | 2023 |
| Smart Chicken Ltd | Hospitality | 2022 |
| Smart Detailing and Protection Supplies Ltd | Manufacturing | 2019 |
| Smart Process & Control Ltd | Manufacturing | 2012 |
| Smart Thames Electrical Limited | Construction | 2016 |
| Smart Windows Limited | Construction | 2015 |
| Smarter Data Protection Limited | Professional & scientific | 2017 |
| Smarter Lending Limited | Financial services | 2018 |
| Smartsightcctv Limited | Administrative & support | 2014 |
| Smartstay Solutions Ltd | Real estate | 2025 |
| Smarttrack Accounting Ltd | Professional & scientific | 2025 |
| Smartview Developments Limited | Real estate | 2023 |
| Smash - the Burger Joint Ltd | Hospitality | 2024 |
| Smash International Limited | Professional & scientific | 2021 |
| Smash Steak Limited | Hospitality | 2024 |
| SMB Recruitment Ltd | Administrative & support | 2023 |
| Smdc Holdings Limited | Professional & scientific | 2007 |
| Smdc Lettings Limited | Real estate | 2026 |
| Smdc Limited | Real estate | 2005 |
| Smidgekins Designs Ltd | Wholesale & retail | 2023 |
| Smithnspoon Limited | Hospitality | 2025 |
| SMK Residential Ltd | Real estate | 2023 |
| Smoke and Buns Ltd | Hospitality | 2025 |
| Smrt Finance Solutions Ltd | Financial services | 2024 |
| SMS Services Ltd | Construction | 2017 |
| SN IT & Soft Ltd | Information & communication | 2020 |
| Snaplanz Limited | Professional & scientific | 2024 |
| Sniper MMA Academy Ltd | Arts & recreation | 2026 |
| Snipit Digital Ltd | Information & communication | 2023 |
| Snowberry Gardens Management Company Limited | Households | 2008 |
| Soar 365 Holdings Ltd | Financial services | 2021 |
| Soarising Ltd | Information & communication | 2020 |
| Social Battery Ltd | Wholesale & retail | 2020 |
| Social Imbibe Ltd | Professional & scientific | 2021 |
| Sofia Vrizidou Ltd | Health & social care | 2022 |
| Soho Editors Talent & Training Ltd | Extraterritorial | 2004 |
| Soho Editors Training Limited | Education | 2000 |
| Soho Media Holdings Limited | Financial services | 2022 |
| Soif Group Limited | Wholesale & retail | 2024 |
| SOL Consultancy Limited | Health & social care | 2025 |
| Solaris Forwarding Limited | Transport & logistics | 2016 |
| Sole Reflextions Ltd | Other services | 2018 |
| Solespirits Limited | Extraterritorial | 2017 |
| Solo Kitchens & Bedrooms Ltd | Manufacturing | 2002 |
| Solo Sprayers Limited | Manufacturing | 1949 |
| Soltec (UK) Limited | Construction | 1996 |
| Somerlea Limited | Households | 2007 |
| SOMETHING2PLAY Limited | Information & communication | 2005 |