| Sine Developments (UK) Limited | Construction | 2020 |
| Sine Homes (UK) Limited | Real estate | 2019 |
| Sine Properties Limited | Real estate | 2019 |
| Singla & Co. Limited | Professional & scientific | 1985 |
| Single Skin Ltd | Wholesale & retail | 2023 |
| Sisu Sound Serenity Ltd | Other services | 2023 |
| SIX Degrees World Ltd | Information & communication | 2025 |
| SIX Seven Property Limited | Real estate | 2024 |
| Sixbob Limited | Professional & scientific | 2012 |
| Sixfortyeight Ltd | Professional & scientific | 2024 |
| Sixty One Outsourcing Solutions Limited | Professional & scientific | 2018 |
| Sizer Street One Limited | Financial services | 2024 |
| Sizer Street Student Accommodation Limited | Real estate | 2023 |
| SJ Teasdale International Ltd | Wholesale & retail | 2022 |
| Sjaj Sourcing Limited | Administrative & support | 2024 |
| SK Sall Limited | Health & social care | 2007 |
| SKD Group Holdings Ltd | Financial services | 2026 |
| Skilled Handyman Services Limited | Construction | 2015 |
| Skillsfaster Ltd | Information & communication | 2022 |
| Skin and Blister Limited | Professional & scientific | 2014 |
| SKM PPV Limited | Professional & scientific | 2019 |
| SKP Electrical & Consultancy Ltd | Professional & scientific | 2026 |
| Skylink Engineering Limited | Manufacturing | 2024 |
| Skymac Properties Limited | Real estate | 2022 |
| Sleep Stays Ltd | Construction | 2025 |
| Sleepless in Soho Limited | Arts & recreation | 2024 |
| Slevins Ltd | Health & social care | 2024 |
| Slicks Tyre & Exhaust Limited | Wholesale & retail | 1995 |
| Slide & Fold Aluminium Limited | Manufacturing | 2023 |
| Sloane Real Estate Ltd | Real estate | 2025 |
| SM CAD and BIM Services Limited | Professional & scientific | 2025 |
| SM Pictures Limited | Information & communication | 2022 |
| Smart Focused Insight Ltd | Professional & scientific | 2025 |
| Smart Hydration Limited | Health & social care | 2018 |
| Smarterclaims Limited | Administrative & support | 2018 |
| Smartparc 2 Limited | Manufacturing | 2018 |
| Smartparc 3 Limited | Manufacturing | 2018 |
| Smartparc 4 Limited | Manufacturing | 2018 |
| Smartparc 5 Limited | Manufacturing | 2018 |
| Smartparc Derby FM Limited | Real estate | 2018 |
| Smartparc Group Limited | Financial services | 2020 |
| Smartparc Limited | Professional & scientific | 2017 |
| Smiling Buddha Limited | Construction | 2021 |
| Smis Enterprises Ltd | Manufacturing | 2007 |
| SMS Microsystem Limited | Information & communication | 2011 |
| SMX2 Property Ltd | Real estate | 2025 |
| Snapsoul Limited | Professional & scientific | 2023 |
| Snells Lane Community Ltd | Real estate | 2002 |
| Snowstorm Limited | Construction | 2010 |
| Snuggies Limited | Information & communication | 2023 |
| Snuggly Spaces Ltd | Real estate | 2025 |
| SO Audio Limited | Information & communication | 2020 |
| Society for Underwater Technology(The) | Other services | 1968 |
| SOH Trading Limited | Other services | 2016 |
| SOH Writing Limited | Other services | 2016 |
| SOL Scenery Limited | Information & communication | 2025 |
| Solas Developments Ltd | Construction | 2012 |
| Solidgain Developments Limited | Real estate | 1997 |
| Solidus Holding Limited | Information & communication | 2016 |
| Solve Sundsbo Limited | Administrative & support | 2010 |
| Soneji Radiology Ltd | Professional & scientific | 2018 |
| Sonnys Riviera Limited | Hospitality | 2025 |
| Sophie Daniels Music Ltd | Extraterritorial | 2007 |
| Soulac Properties Ltd | Real estate | 2023 |
| South Park Mews (Gerrards Cross) Management Company Ltd | Households | 2019 |
| South Promo Limited | Construction | 2010 |
| South View Road Limited | Households | 2006 |
| Southern Electrical Services Limited | Construction | 1996 |
| Southland Consultancy Ltd | Professional & scientific | 2024 |
| Sovereign Freehold Ltd | Real estate | 2014 |
| Sovereign Property Management Services Limited | Construction | 2016 |
| SPA52 Ltd | Real estate | 2017 |
| Spanna Ltd | Wholesale & retail | 2022 |
| Sparkles Global Limited | Arts & recreation | 2023 |
| Sparsholt Ltd | Real estate | 2021 |
| Speak NO Evil Limited | Professional & scientific | 2017 |
| Specialist Care Provision Ltd | Health & social care | 2023 |
| Specialist MGA Limited | Extraterritorial | 2016 |
| Sphere Design Limited | Professional & scientific | 2023 |
| Spinta Digital Ltd | Professional & scientific | 2020 |
| Spirant Computantis Limited | Professional & scientific | 2018 |
| Spirit Conference Sets Limited | Construction | 2004 |
| Spiro Market Research Limited | Professional & scientific | 2025 |
| Springboard Health Partners Limited | Professional & scientific | 2025 |
| SPS People Limited | Professional & scientific | 2026 |
| SPV EQ Limited | Information & communication | 2018 |
| SQJ Limited | Wholesale & retail | 2012 |
| Square Electric Datacomms Ltd | Construction | 2019 |
| Square Plugins Limited | Information & communication | 2015 |
| SRI SAI Consulting Services Ltd | Information & communication | 2011 |
| Srsh Consultancy Ltd | Information & communication | 2022 |
| SSC Interim Services Limited | Financial services | 2015 |
| SSN Consultancy Limited | Other services | 2017 |
| Sssal Operating Company Limited | Real estate | 2024 |
| Ssst Limited | Real estate | 2024 |
| ST Huberts Limited | Professional & scientific | 2009 |
| ST Joseph Care Ltd | Health & social care | 2014 |
| ST Maur Pictures Ltd | Information & communication | 2020 |
| St-Philly Limited | Hospitality | 2025 |
| ST. Margaret's Court Management (ST. Margarets) Limited | Households | 1995 |