| Silver Walk Management Limited | Households | 1987 |
| Silvermount Traders Limited | Administrative & support | 1995 |
| Simat Holdings Ltd | Financial services | 2018 |
| Simi Properties Ltd | Real estate | 2022 |
| Simon Smith Heating and Plumbing Ltd | Construction | 2017 |
| Simpletag Ltd | Information & communication | 2014 |
| Simply Beautiful Limited | Real estate | 2001 |
| Simply Human Resources Ltd | Administrative & support | 2024 |
| Simply Tailored Ltd | Other services | 2019 |
| Sims IT Limited | Information & communication | 2011 |
| Sina Investments Ltd | Administrative & support | 2012 |
| Sinenomine Ltd | Professional & scientific | 2010 |
| Sinex Limited | Wholesale & retail | 2012 |
| Sinfonica Limited | Other services | 2008 |
| Singer & Friedlander Limited | Financial services | 2016 |
| Singh Family Happy Homes Ltd | Administrative & support | 2014 |
| Singlecustomerviews Limited | Information & communication | 2016 |
| Sisiri Limited | Construction | 2024 |
| Sister Studios Ltd | Professional & scientific | 2017 |
| SIV Fire Protection Ltd | Construction | 2010 |
| SJG Properties Ltd | Real estate | 2017 |
| Sjgh Ltd | Real estate | 2025 |
| SJW Academy Ltd | Arts & recreation | 2025 |
| SJW Elite Ltd | Arts & recreation | 2025 |
| SJW Sports Group Limited | Arts & recreation | 2017 |
| SK Movers Limited | Administrative & support | 2010 |
| SK2 Ltd | Wholesale & retail | 2024 |
| Skape London Ltd | Construction | 2020 |
| SKG Limited | Wholesale & retail | 2023 |
| Skills Republic Ltd | Education | 2016 |
| Skin Camouflage Consultancy Ltd | Health & social care | 2018 |
| Skin Camouflage International Ltd | Education | 2023 |
| Skinbiotics UK Ltd | Wholesale & retail | 2025 |
| Skinwise London Limited | Other services | 2024 |
| Skittleface Productions Limited | Information & communication | 2014 |
| SKN HII Limited | Other services | 2019 |
| Skylight Centre Ltd | Real estate | 2024 |
| Slade Formwork Ltd | Construction | 2016 |
| Sleek Hair Ltd | Other services | 2025 |
| Slim Property Ltd | Real estate | 2017 |
| SLM Properties Limited | Real estate | 2018 |
| SLS Media London Ltd | Administrative & support | 2015 |
| SLS Print Limited | Manufacturing | 2003 |
| Smallworld Distribution UK Limited | Other services | 2015 |
| Smart Security Group Ltd | Administrative & support | 2023 |
| Smart Sparks Solutions Ltd | Construction | 2020 |
| Smartfinal Property Management Limited | Households | 1988 |
| Smartplayds Limited | Public administration | 2015 |
| Smash Guys Ltd | Hospitality | 2026 |
| SMB Sunset Limited | Households | 2025 |
| SMG Capital Ltd | Real estate | 2024 |
| Smgb Business Academy Ltd | Education | 2024 |
| Smile Art Dental Ltd | Extraterritorial | 2012 |
| Smiles PER Miles Limited | Arts & recreation | 2020 |
| Smith Music Company Limited | Arts & recreation | 1984 |
| Smiths Schoolwear Holdings Limited | Financial services | 2023 |
| Smokingpanda Limited | Other services | 2009 |
| Smpuk Limited | Information & communication | 2023 |
| Smpventures Ltd | Real estate | 2025 |
| Snazzy Promotions Limited | Administrative & support | 1997 |
| Snowbest Limited | Real estate | 1919 |
| SOA Property Limited | Real estate | 2020 |
| Social Optimum Ltd | Professional & scientific | 2020 |
| Sofrankie Productions Limited | Information & communication | 2022 |
| Softaware Limited | Information & communication | 2001 |
| Software & Consulting Europe Ltd | Information & communication | 1999 |
| Solakinsche Limited | Real estate | 2024 |
| Solaris Green Energies Limited | Manufacturing | 2015 |
| Soldout Distribution Ltd | Wholesale & retail | 2025 |
| Solitude Brands Limited | Wholesale & retail | 2022 |
| Solo Collect Holdings Ltd | Financial services | 2022 |
| Solo Investments Limited | Construction | 2012 |
| Something Else Events Ltd | Hospitality | 2018 |
| Sonat Cafe Limited | Hospitality | 2023 |
| Sonih Investments Limited | Real estate | 2000 |
| Sonmez Properties Ltd | Real estate | 2021 |
| Sophing Advertising Ltd | Professional & scientific | 2026 |
| Sophrena Limited | Professional & scientific | 2014 |
| SOS Housing Services Ltd | Real estate | 2018 |
| Sosa Architects Limited | Professional & scientific | 2019 |
| Sosoli’S Constructions Limited | Manufacturing | 2021 |
| Sought Homes Ltd | Real estate | 2026 |
| Sound Mynds Limited | Education | 2022 |
| Sourcechange Limited | Professional & scientific | 2023 |
| South Hertfordshire Developments Ltd | Construction | 2004 |
| South Kensington Clinic Ltd | Administrative & support | 2022 |
| South Mimms AKH Limited | Real estate | 2025 |
| South River Investments Limited | Professional & scientific | 2024 |
| Southern Cross Automation Limited | Administrative & support | 2013 |
| Southwood Property Company Limited(The) | Real estate | 1962 |
| Southwood Property Group Limited | Real estate | 2020 |
| Souvlaki Pro Limited | Hospitality | 2019 |
| Sovereign Security Solutions Ltd | Administrative & support | 2024 |
| Soviva Group Ltd | Administrative & support | 2024 |
| SP 121 Ltd | Professional & scientific | 2024 |
| Space Architecture+Planning Limited | Professional & scientific | 2009 |
| Space for ALL - Property Ltd | Real estate | 2026 |
| Spaceplus Builders Limited | Construction | 2025 |
| Spacepro Limited | Extraterritorial | 2014 |
| Spandorr Limited | Other services | 2003 |