| Sills Properties Limited | Real estate | 2026 |
| Sills Property LLP | | 2024 |
| Silo Foods Ltd | Hospitality | 2020 |
| Silueta Productions Limited | Information & communication | 2026 |
| Silvana Marketing Ltd | Professional & scientific | 2026 |
| Silvarose Jewellery Ltd | Wholesale & retail | 2025 |
| Silver Beard Images Limited | Professional & scientific | 2016 |
| Silver Circle Property 1 Ltd | Real estate | 2022 |
| Silver Circle Property 2 Ltd | Real estate | 2022 |
| Silver Circle Property Ltd | Construction | 2017 |
| Silver Cloud Kitchen Ltd | Hospitality | 2025 |
| Silver Club Construct Ltd | Construction | 2022 |
| Silver FOX Distribution Ltd | Other services | 2023 |
| Silver Harbour Films Ltd | Arts & recreation | 2026 |
| Silver House Solutions Limited | Information & communication | 2015 |
| Silver Key Estates and Management Limited | Real estate | 2025 |
| Silver Lava Limited | Hospitality | 2017 |
| Silver Moon Trading (UK) Limited | Wholesale & retail | 2017 |
| Silver Next Ltd | Wholesale & retail | 2025 |
| Silver OWL Marketing Ltd | Professional & scientific | 2024 |
| Silver Palm Holdings Ltd | Real estate | 2026 |
| Silver Rock Properties Limited | Real estate | 2024 |
| SILVER7777 Ltd | Wholesale & retail | 2021 |
| Silverback Fit Ltd | Construction | 2018 |
| Silverdale Project UK Limited | Construction | 2018 |
| Silverdragon Wellbeing Ltd | Health & social care | 2017 |
| Silverfly Services Ltd | Wholesale & retail | 2021 |
| Silverguard Limited | Manufacturing | 2018 |
| Silverlink Technologies Ltd | Information & communication | 2003 |
| Silverpearl Capital Limited | Professional & scientific | 2012 |
| Silvershot Limited | Other services | 2001 |
| Silverspoon Media Limited | Information & communication | 2005 |
| Silverstream Properties Limited | Construction | 2000 |
| Silvertech Support Ltd | Information & communication | 2013 |
| Silvertip Limited | Information & communication | 1998 |
| Silvertouch Professional Services Limited | Professional & scientific | 2012 |
| SIM VIK Ltd | Construction | 2013 |
| Simandhar Swami LLP | | 2013 |
| Simat Properties Limited | Construction | 1963 |
| Simba Property (UK) Limited | Real estate | 2017 |
| Simba Property (UK) Trading Limited | Real estate | 2020 |
| Simba Property Commercial 2 Limited | Hospitality | 2023 |
| Simba Property Commercial Ltd | Real estate | 2023 |
| Simenon.Tm Limited | Professional & scientific | 2005 |
| Simgold Limited | Wholesale & retail | 1977 |
| Simma Properties Limited | Real estate | 2018 |
| SIMMAR2814 Limited | Construction | 2020 |
| Simmi Properties Ltd | Real estate | 2022 |
| Simmo Compressors Ltd | Wholesale & retail | 2022 |
| Simo Management Ltd | Households | 2016 |
| Simocha Ltd | Wholesale & retail | 2022 |
| Simon Brickwork Ltd | Construction | 2017 |
| Simon Martin Search Limited | Administrative & support | 2010 |
| Simon Multibuild Ltd | Construction | 2026 |
| Simon Ratigan Limited | Information & communication | 2009 |
| Simon Waldock Limited | Administrative & support | 2015 |
| Simons Quality Ltd | Transport & logistics | 2014 |
| Simp Estates Limited | Real estate | 2024 |
| Simpatico Design Limited | Professional & scientific | 2022 |
| Simplaa UK Limited | Transport & logistics | 2018 |
| Simple Reputation Limited | Information & communication | 2024 |
| Simple Trade Limited | Wholesale & retail | 2016 |
| Simpleone Services PVT Limited | Professional & scientific | 2023 |
| Simplerevenue Limited | Hospitality | 2021 |
| Simplexity Consult Ltd | Professional & scientific | 2023 |
| Simplif Ltd | Professional & scientific | 2021 |
| Simplified Immigration Limited | Other services | 2011 |
| Simplified Sourcing Ltd | Real estate | 2017 |
| Simply Brands Direct Limited | Wholesale & retail | 2005 |
| Simply Digital Consulting Limited | Information & communication | 2015 |
| Simply Easy Cleaning Services Ltd | Administrative & support | 2026 |
| Simply Food Kitchen Ltd | Hospitality | 2021 |
| Simply Graphics Ltd | Professional & scientific | 2019 |
| Simply Sailing Ltd | Transport & logistics | 2025 |
| Simply SEV Snacks Limited | Manufacturing | 2019 |
| Simply Tax Online Limited | Professional & scientific | 2020 |
| Simpsons Chicken and Pizza Ltd | Hospitality | 2025 |
| Simpsons Express Ltd | Hospitality | 2024 |
| Simraj Trader Ltd | Wholesale & retail | 2025 |
| Simran Enterprise Ltd | Real estate | 2023 |
| Simran Solutions Ltd | Professional & scientific | 2016 |
| Simsim Kitchen Limited | Hospitality | 2022 |
| Simy AVN Ltd | Transport & logistics | 2025 |
| SIN2 Mini Store Limited | Wholesale & retail | 2013 |
| Sinai (Antiques) Limited | Wholesale & retail | 1977 |
| Sinaj Lofts Ltd | Construction | 2018 |
| Sincere Engineering Limited | Professional & scientific | 2020 |
| Sinckot Capital Limited | Real estate | 2014 |
| Sinckot Development (Heston) Limited | Construction | 2017 |
| Sinckot Developments Ltd | Construction | 2014 |
| Sinckot Properties (Harrow) Limited | Real estate | 2024 |
| Sinckot Properties (Heston) Limited | Real estate | 2020 |
| Sinckot Properties (Knot) Ltd | Real estate | 2018 |
| Sinckot Properties (KNOT2) Limited | Real estate | 2019 |
| Sinckot Properties Limited | Real estate | 2005 |
| Sinclair Mckinsley Consultants Limited | Professional & scientific | 2019 |
| Sinclair Mckinsley Limited | Professional & scientific | 2010 |
| Sinclair Solomons Limited | Information & communication | 1992 |
| Sinclair Solomons Management Limited | Households | 2025 |
| Sinclair Ventures Limited | Construction | 1984 |