| Sinsat Properties Ltd | Real estate | 2022 |
| Sintoxone Limited | Information & communication | 2019 |
| SIO2 Ltd | Construction | 2016 |
| Sip'N'Scent Ltd | Wholesale & retail | 2025 |
| Siri Business Solutions Limited | Information & communication | 2013 |
| Sirmoor Aviation Ltd | Administrative & support | 2010 |
| Sisi Bar & Kitchen Ltd | Hospitality | 2025 |
| Sisu Imaging Services Ltd | Professional & scientific | 2022 |
| Sivsha Limited | Health & social care | 2025 |
| SIX HAT Solutions Limited | Professional & scientific | 2011 |
| Sixforty IS Home Ltd. | Wholesale & retail | 2024 |
| Sixth Sense Intelligence Limited | Professional & scientific | 2013 |
| Sizzle MIX Ltd | Wholesale & retail | 2023 |
| Sjain Properties Ltd | Real estate | 2022 |
| SJK1 Limited | Real estate | 2018 |
| SJK2 Limited | Financial services | 2019 |
| Sjmg Ltd | Wholesale & retail | 2024 |
| Sjp(Uk) Limited | Health & social care | 2018 |
| SK Alpha Ltd | Administrative & support | 2016 |
| SK Alpha Properties Ltd | Real estate | 2016 |
| SK and Sons Property Ltd | Real estate | 2025 |
| SK Design Studio Limited | Professional & scientific | 2020 |
| SK Foods Limited | Wholesale & retail | 1995 |
| SKA Services Limited | Financial services | 2018 |
| Skarvi Systems Limited | Information & communication | 2019 |
| Skill Match Resources Ltd | Education | 2003 |
| Skillar Consulting Limited | Professional & scientific | 2015 |
| Skin Cosmetic Doctors Ltd | Health & social care | 2019 |
| Skin GT Limited | Health & social care | 2025 |
| Skintonym Ltd | Health & social care | 2013 |
| Skipman Environmental Management Ltd | Water & waste | 2021 |
| Skjm Holdings Limited | Real estate | 2026 |
| SKL Sounds Limited | Wholesale & retail | 2025 |
| Skozy Limited | Real estate | 2023 |
| SKR Wealth Management Ltd | Financial services | 2016 |
| SKS Accountancy and Professional Services Limited | Professional & scientific | 2009 |
| SKT Properties (UK) Limited | Real estate | 2016 |
| Sky Smith Ltd | Wholesale & retail | 2025 |
| SKYCHANG1526 Limited | Information & communication | 2019 |
| Skylark Property Investment Ltd | Real estate | 2017 |
| Skymech Properties Limited | Real estate | 2006 |
| SKYO9 Limited | Real estate | 2018 |
| Skyros Design & Build Ltd | Construction | 2015 |
| Skyros Property Management Ltd | Real estate | 2019 |
| Skytale Limited | Information & communication | 2021 |
| Skywell Limited | Information & communication | 2007 |
| SL4Z Limited | Real estate | 2022 |
| Slade (London) Ltd | Administrative & support | 2011 |
| Slik Developments Ltd | Real estate | 2021 |
| SLY Bear Ltd | Professional & scientific | 2011 |
| SM Investment Management Ltd | Professional & scientific | 2016 |
| SM London Construction Limited | Construction | 2015 |
| Small World Community Nursery Ltd. | Education | 2001 |
| Small World Nursery (Watford) CIC | Health & social care | 2019 |
| Smar Group Ltd | Financial services | 2020 |
| Smar Hotels & Leisure Ltd | Hospitality | 2024 |
| Smar Hotels Ltd | Hospitality | 2024 |
| Smar Space Ltd | Real estate | 2018 |
| Smart Appliances Ltd | Wholesale & retail | 2018 |
| Smart Developing Ltd | Real estate | 2016 |
| Smart END of Tenancy Cleaning Limited | Administrative & support | 2025 |
| Smart Food Packaging Ltd | Extraterritorial | 2025 |
| Smart Payroll Solutions Ltd | Other services | 2024 |
| Smart Property Insider Ltd | Real estate | 2017 |
| Smart Risk Alpha Ltd | Financial services | 2021 |
| Smart Riskpremia Ltd | Financial services | 2019 |
| Smart Source Savings Ltd | Professional & scientific | 2025 |
| Smart Teach & Vape Limited | Wholesale & retail | 2024 |
| Smartclarke Ltd | Professional & scientific | 2018 |
| Smarter Electrics Limited | Construction | 2022 |
| Smartpremia Ltd | Financial services | 2019 |
| SME Merchant Services Global Ltd | Administrative & support | 2022 |
| Smile Consultancy Limited | Health & social care | 2022 |
| Smiles by SJ Limited | Health & social care | 2016 |
| Smithfield Shoe Company Limited | Wholesale & retail | 2026 |
| Smoke & Events Ltd | Hospitality | 2019 |
| Smokin LAB Limited | Hospitality | 2024 |
| Smts Consulting Ltd | Information & communication | 2021 |
| Sniff & Swagger Limited | Wholesale & retail | 2024 |
| Snippetsbox Ltd | Information & communication | 2013 |
| SNJ International Limited | Real estate | 2007 |
| SNK Advisory Ltd | Administrative & support | 2014 |
| Snmk Group Ltd | Real estate | 2018 |
| Snowflake Holding Ltd | Financial services | 2021 |
| SNS Homes Ltd | Real estate | 2017 |
| Sntp Services Ltd | Information & communication | 2014 |
| SO Web Limited | Other services | 2022 |
| Sobriety and Wellbeing Ltd | Health & social care | 2023 |
| Social Developments UK Limited | Real estate | 2004 |
| Social Production House Ltd | Professional & scientific | 2023 |
| Sofia Turner London Limited | Wholesale & retail | 2024 |
| Sohal Haulage Ltd | Transport & logistics | 2014 |
| Sohini Badiani Limited | Health & social care | 2023 |
| Sohnik Properties Limited | Real estate | 2011 |
| Sojo Creative Ltd | Professional & scientific | 2021 |
| Sola Creates Limited | Manufacturing | 2023 |
| Solas PAY Limited | Administrative & support | 2022 |
| Solid Axis Ltd | Real estate | 2025 |
| Solis Power Limited | Manufacturing | 2024 |
| Solo Green Renewable Limited | Construction | 2022 |