| Shubh Parekh Ltd | Administrative & support | 2024 |
| Shudh Investments Limited | Real estate | 2019 |
| Shudh Ipco Limited | Information & communication | 2020 |
| Shukal Logistics Ltd | Transport & logistics | 2017 |
| Shumharrow Holding Limited | Real estate | 2024 |
| Shumtone Limited | Other services | 2024 |
| Shun BUN GEN FAT Trade Co Limited | Wholesale & retail | 2026 |
| Shura Properties Ltd | Real estate | 2022 |
| Shuruat Ltd | Professional & scientific | 2010 |
| Shutter Your House Limited | Construction | 2019 |
| Shuttle Aviation Ltd | Administrative & support | 1998 |
| SHY Firefly Ltd | Wholesale & retail | 2022 |
| Shyam Engineering Ltd | Professional & scientific | 2013 |
| Shyam Investments Limited | Real estate | 2021 |
| Shyam Radhe | Education | 2025 |
| Shyam's Trading Ltd | Wholesale & retail | 2024 |
| Shyamrath Limited | Wholesale & retail | 2026 |
| Shyamsagar Ltd | Hospitality | 2024 |
| Shyn LLP | | 2023 |
| Shynex Cleaning Services Ltd | Administrative & support | 2025 |
| SI Property Management Ltd | Real estate | 2000 |
| SI Research Limited | Administrative & support | 2009 |
| Si&T Consulting Limited | Information & communication | 2010 |
| SI29 Limited | Information & communication | 2004 |
| SIA Alipour Limited | Arts & recreation | 2022 |
| SIA Drinks Ltd | Wholesale & retail | 2023 |
| SIA Licence Ltd | Administrative & support | 2024 |
| Siam Nuad Thai Massage Ltd | Other services | 2025 |
| Siam Thai Massage & Spa Limited | Health & social care | 2022 |
| Siara Logistic Ltd | Transport & logistics | 2025 |
| Sican Limited | Hospitality | 2022 |
| Sicsic Advisory Ltd | Professional & scientific | 2019 |
| Sicsic Holdings Limited | Financial services | 2020 |
| Sicsic Opco Ltd | Wholesale & retail | 2023 |
| Sidaryan Consultancy Ltd. | Information & communication | 2013 |
| Sidaryan Property Ltd | Real estate | 2021 |
| Siddhayu Europe Ltd | Wholesale & retail | 2024 |
| Siddhi Ganesha Ltd | Hospitality | 2025 |
| Siddhi International Limited | Wholesale & retail | 2021 |
| Siddhi Property & Consultancy Ltd | Real estate | 2025 |
| Siddhisri Limited | Professional & scientific | 2015 |
| Siddiq Solutions Limited | Information & communication | 2025 |
| Sidhu Fast Food Ltd | Hospitality | 2017 |
| Sidhu Surgery Ltd | Health & social care | 2024 |
| Sidiqigroup Ltd | Wholesale & retail | 2025 |
| Sidlink Group Ltd | Information & communication | 2023 |
| Sidney Cubbage (Engineers) Limited | Extraterritorial | 1945 |
| Sidney Newton Holdings Limited | Administrative & support | 1959 |
| Sidney Newton Limited | Real estate | 1950 |
| Sidtech Limited | Administrative & support | 2009 |
| Sidtech Umbrella Ltd | Administrative & support | 2015 |
| SIE Building Limited | Construction | 2021 |
| Sienna Care Limited | Health & social care | 2010 |
| Sienna Rose Enterprise Ltd | Other services | 2013 |
| Sienna Services(Uk) Ltd | Hospitality | 2019 |
| Sienna Ventures Limited | Construction | 2025 |
| Sierra Capital Finance Limited | Financial services | 2020 |
| Sifo Construction Ltd | Construction | 2019 |
| Sigas Trans Ltd | Transport & logistics | 2025 |
| Sigitus London Ltd | Construction | 2020 |
| Sigma Autos Ltd | Wholesale & retail | 2019 |
| Sigma Consultants Limited | Professional & scientific | 2018 |
| Sigma MED Ltd | Wholesale & retail | 2020 |
| Sigma Motors (UK) Limited | Wholesale & retail | 2024 |
| Sigma Union Ltd | Hospitality | 2025 |
| Sigmango Ltd | Wholesale & retail | 2025 |
| Sign Seal Deliver Ltd | Transport & logistics | 2025 |
| Sign Works London Limited | Professional & scientific | 2024 |
| Signal Hire Ltd | Administrative & support | 2022 |
| Signal Test Limited | Administrative & support | 2012 |
| Signalling Installation & Maintenance Services Limited | Professional & scientific | 1994 |
| Signalling Testing & Support Limited | Administrative & support | 2004 |
| Signature Capital Global Ltd | Professional & scientific | 2019 |
| Signature Spirits Ltd | Wholesale & retail | 2026 |
| Signature Tailoring Ltd | Other services | 2025 |
| Signia Space Management Limited | Real estate | 2015 |
| Signvilla Ltd | Manufacturing | 2022 |
| Signworks Incorporation Limited | Professional & scientific | 2014 |
| SIK Cleaning Limited | Administrative & support | 2018 |
| Sikandar Optiks UK Ltd | Professional & scientific | 2025 |
| Sikraft Infotech (Nuclear Energy) Limited | Professional & scientific | 2020 |
| Siksha UK Limited | Administrative & support | 2013 |
| Silantro Ltd | Hospitality | 2017 |
| Silda Fine Art Limited | Wholesale & retail | 2024 |
| Sile Trans Ltd | Transport & logistics | 2015 |
| Silent Canvas Films Ltd | Information & communication | 2026 |
| Silent Farm Dream Ltd | Manufacturing | 2024 |
| Silent Ltd | Administrative & support | 2015 |
| Silent River Ltd | Information & communication | 2021 |
| Silent Stone Trading Ltd | Wholesale & retail | 2026 |
| Silentstays Ltd | Real estate | 2023 |
| Sileva Limited | Transport & logistics | 2025 |
| Silicon Business Centre (Management) Limited | Real estate | 1996 |
| Silicon Stream Consultancy Limited | Information & communication | 2015 |
| Silk Contracts Limited | Construction | 2017 |
| Silk Road Eastern Essence Ltd | Wholesale & retail | 2023 |
| Silk Route Supplies Limited | Wholesale & retail | 2023 |
| Silkline Travel UK Ltd | Administrative & support | 2022 |
| Silktone Violin Products Limited | Manufacturing | 2003 |
| Silkysell Ltd | Wholesale & retail | 2025 |