| Sharps Property Services Ltd | Construction | 2019 |
| Shawn Williams Caribbean Foods Ltd | Wholesale & retail | 2021 |
| She's GOT IT Sorted Ltd | Hospitality | 2022 |
| Shea Sports Limited | Manufacturing | 2016 |
| Sheenrose Limited | Information & communication | 1989 |
| Shenghai Limited | Hospitality | 2025 |
| Sherni Sports Management Ltd | Professional & scientific | 2022 |
| Sherwood House Ltd | Professional & scientific | 2002 |
| Shieling Management Company Limited | Households | 2014 |
| Shine LDN Ltd | Wholesale & retail | 2020 |
| Shinerhilldesign Ltd | Information & communication | 2021 |
| Shiro's World Ltd | Wholesale & retail | 2025 |
| Shivika Ltd | Wholesale & retail | 2023 |
| Showcase Creative Ltd | Manufacturing | 2018 |
| Shrestha Griha Limited | Real estate | 2022 |
| Shukrana Limited | Wholesale & retail | 2018 |
| Sicard Ltd | Financial services | 2020 |
| Sid-Tsno Limited | Transport & logistics | 2023 |
| Siddhartha Gautam Limited | Health & social care | 2019 |
| Sidelka Ltd | Administrative & support | 2022 |
| Siemens Benefits Scheme Limited | Professional & scientific | 1990 |
| Siemens Electronic Design Automation Ltd | Information & communication | 1983 |
| Siemens Emobility Charging Limited | Manufacturing | 2021 |
| Siemens Holdings PLC | Professional & scientific | 1990 |
| Siemens Industry Software Limited | Information & communication | 1997 |
| Siemens Pension Funding (General) Limited | Financial services | 2012 |
| Siemens Pension Funding Limited | Financial services | 2012 |
| Siemens PLC | Manufacturing | 1962 |
| Siemens Power Generation Limited | Professional & scientific | 1997 |
| Sierra Productions Limited | Information & communication | 2014 |
| Siga Homes Limited | Real estate | 2020 |
| Siga UK Limited | Administrative & support | 2009 |
| Sign & Brand Ltd | Manufacturing | 2020 |
| Signature Build Ltd | Construction | 2024 |
| Signature Catering Ltd | Manufacturing | 2018 |
| Signiq Ltd | Information & communication | 2026 |
| SII Services Limited | Professional & scientific | 2015 |
| Silicair Dryers Limited | Manufacturing | 1967 |
| Silicair Dryvent Limited | Manufacturing | 2002 |
| Silk Signs Limited | Manufacturing | 2001 |
| Silva Forest Solutions Ltd | Information & communication | 2024 |
| Silver Arch Financial Limited | Financial services | 2023 |
| Silver Sea Group Ltd | Hospitality | 2019 |
| Silverlight Limited | Hospitality | 2008 |
| Silvester Brothers Cycles Ltd | Wholesale & retail | 2024 |
| Simeous Ltd | Professional & scientific | 2014 |
| Simon Paxton Building Services Limited | Construction | 2014 |
| Simplicity AI Limited | Information & communication | 2007 |
| Simply Skin London Limited | Other services | 2010 |
| Simpson Financial Limited | Professional & scientific | 2020 |
| Simpsons Consultancy Limited | Professional & scientific | 2010 |
| Simwood Investments Limited | Real estate | 2013 |
| Sinking Birdies Ltd | Wholesale & retail | 2023 |
| SIXTEEN0SIX Limited | Other services | 2016 |
| Sixworks Limited | Information & communication | 2017 |
| Siya Properties Limited | Hospitality | 1999 |
| SJC Electrical Services (Southern) Limited | Construction | 2012 |
| SJK Servicing Limited | Manufacturing | 2016 |
| SK South Leisure Ltd | Real estate | 2021 |
| Skin Geeks Limited | Real estate | 2009 |
| SKS Construction and Builders Private Limited | Construction | 2025 |
| Sky Event Planner Limited | Hospitality | 2017 |
| Sky Ladder Construction Limited | Construction | 2021 |
| Sky Lofts Ltd | Construction | 2013 |
| Skybase IT Limited | Information & communication | 2015 |
| Skyla Blossom Limited | Construction | 2010 |
| Skyla Consulting Limited | Other services | 2009 |
| Skyline Agencies Limited | Wholesale & retail | 2011 |
| Skylona Limited | Wholesale & retail | 2024 |
| Skynex Global Solutions Ltd | Information & communication | 2023 |
| Skywalker Operations Limited | Transport & logistics | 2023 |
| SL Logistics Ltd | Transport & logistics | 2015 |
| SL Tree Surgery Ltd | Administrative & support | 2021 |
| Sleet Views Limited | Real estate | 2016 |
| Slmss Properties LLP | | 2026 |
| Slough Sushi Ltd | Hospitality | 2023 |
| Smart Choice FNB Limited | Wholesale & retail | 2023 |
| Smart Recruiting Ltd | Administrative & support | 2015 |
| Smart Security Systems Limited | Administrative & support | 2001 |
| Smartclear Solutions Limited | Water & waste | 2021 |
| Smarter Brains Ltd | Professional & scientific | 2024 |
| Smartsheetspro Ltd | Wholesale & retail | 2025 |
| Smartt Software Limited | Information & communication | 1990 |
| Smarttasking.Com Limited | Information & communication | 2015 |
| Smash Media Limited | Information & communication | 2007 |
| SME Displays Ltd | Wholesale & retail | 2019 |
| SME Systems Ltd | Professional & scientific | 2012 |
| SMG Services Ltd | Construction | 2019 |
| Smile Metamorphosis Limited | Other services | 2024 |
| Smiles at School Limited | Professional & scientific | 2020 |
| Smir Consultancy Limited | Administrative & support | 2022 |
| Smith & Redpath Renovations Ltd | Construction | 2025 |
| SMT Property Limited | Real estate | 2019 |
| Snap Engineering Ltd | Professional & scientific | 2012 |
| SNK Properties & Development Limited | Real estate | 2016 |
| SNK Trading Ltd | Information & communication | 2011 |
| Snoozin Ltd | Real estate | 2025 |
| Snow Foam Car Wash Ltd | Other services | 2026 |
| Snowy Bidco Limited | Financial services | 2022 |
| Snowy Midco 1 Limited | Financial services | 2022 |