| Sharon Slattery Consulting Limited | Other services | 2016 |
| Shavegold Limited | | 1986 |
| Shaw Park (Crowthorne) Management Co. Limited | Households | 1998 |
| Sheevely Enterprises Ltd | Wholesale & retail | 2024 |
| Showmove Limited | Transport & logistics | 2003 |
| Showmoves Ltd | Transport & logistics | 1991 |
| Shsb Investments Limited | Real estate | 1997 |
| Signia Studio Ltd | Wholesale & retail | 2024 |
| Silverfern Builders Ltd | Construction | 2006 |
| Silverlake Limited | Information & communication | 1997 |
| Simon Coupland Ltd | | 1993 |
| Simon Perris Construction Limited | Construction | 2004 |
| Singleton Limited | Professional & scientific | 2002 |
| Sirun Limited | Information & communication | 2007 |
| SKC Consulting Limited | Professional & scientific | 2016 |
| Skills SET Limited | Education | 2006 |
| Skylift Limited | Transport & logistics | 1998 |
| Slonce Ltd | Wholesale & retail | 2019 |
| Slough Council for Voluntary Service | Health & social care | 1998 |
| SM Finance Resource Ltd | Professional & scientific | 2013 |
| Smith and Co. Consultant Surveyors Limited | Real estate | 1994 |
| Smoke Hub Ltd | Wholesale & retail | 2025 |
| Smyth (Engineering) Limited | Administrative & support | 1997 |
| Snap-On Group Holdings Limited | Professional & scientific | 2025 |
| Snns Properties Ltd | Real estate | 2024 |
| Soccer Elite Football Academy Limited | Arts & recreation | 2005 |
| Solid State Disks Ltd | Information & communication | 2008 |
| Solomon Wise Limited | Real estate | 2007 |
| Solutions for Growth Limited | Professional & scientific | 2004 |
| Solvyrion Ltd | Wholesale & retail | 2026 |
| Sonet Dormant Company NO. 1 Limited | Financial services | 1927 |
| South Bucks Properties Limited | | 1958 |
| South Hill Park Trust Limited | Arts & recreation | 1973 |
| Sovereign Taxi Ltd | Administrative & support | 2018 |
| Space (L & M) Limited | Real estate | 2007 |
| Spaulding and Holmes Limited | Real estate | 1953 |
| Speakers Associates Limited | Professional & scientific | 1999 |
| Spechome Limited | Construction | 2004 |
| Speech Sort Limited | Health & social care | 2002 |
| Speedadapt Limited | Real estate | 1996 |
| Spend UP Ltd | Wholesale & retail | 2025 |
| Spiralincome Public Limited Company | Arts & recreation | 1992 |
| SPJ Electrical Ltd | Construction | 2016 |
| Spooner & Co Limited | Professional & scientific | 2002 |
| Sportline Limited | Extraterritorial | 1993 |
| Sportmate Limited | Professional & scientific | 2003 |
| SQL Personnel Limited | Information & communication | 2000 |
| SR2 Consultants Limited | Professional & scientific | 2005 |
| SRI Saradhi IT Solutions Ltd | Information & communication | 2017 |
| Srivikorn Group (UK) Limited | Hospitality | 1998 |
| ST Mary's School Ascot | Education | 1984 |
| ST. Fillan Housing Limited | Real estate | 1999 |
| ST. George's School Ascot Trust Limited | Education | 1967 |
| Stags (Caversham) Limited | Administrative & support | 2001 |
| Stanlake Park Company Limited | Agriculture & fishing | 1978 |
| Staples & King Lettings Limited | Real estate | 2004 |
| Staples & King Limited | Real estate | 2002 |
| Staples Investments Limited | Real estate | 1997 |
| Starmglen Limited | Real estate | 1973 |
| Starwood Court Management Company (1991) Limited | Households | 1991 |
| Staxlink Ltd | Construction | 2003 |
| Steamship Records Limited | Hospitality | 1977 |
| Steano Ltd | Wholesale & retail | 2022 |
| Stearn Electric Company Pension Trustees Limited | Professional & scientific | 2018 |
| Stepthotix Consultancy Limited | Health & social care | 2021 |
| Sterling Components Limited | Extraterritorial | 1983 |
| Stevemar Metal Reclamations Limited | Water & waste | 1977 |
| Stirrups Hotel Limited | Hospitality | 2007 |
| Stonehill Gate Limited | Households | 2000 |
| Stonehouse Autos Limited | Wholesale & retail | 1999 |
| Stoney Lane Management Company Limited | Professional & scientific | 1988 |
| Stop 'N' Shop (Slough) Limited | Wholesale & retail | 2002 |
| Stoplock Limited | Extraterritorial | 1977 |
| Stratfield Mortimer Community Centre Community Interest Company | Real estate | 2006 |
| Street Property Management Limited | Real estate | 2021 |
| Stress Consultants Limited | Construction | 2007 |
| Strikebow Limited | Construction | 1989 |
| Suddensource Limited | Information & communication | 1996 |
| Suedon Limited | Information & communication | 1990 |
| Sultan Balti House Limited | Hospitality | 2003 |
| Summerleaze Limited | Agriculture & fishing | 1983 |
| Summerleaze Waste Limited | Extraterritorial | 1946 |
| Summertown Real Estate Limited | Real estate | 2025 |
| Summit Education Trust | Education | 2025 |
| Summit Office Services Limited | Professional & scientific | 1965 |
| Sun Sung Limited | Real estate | 2005 |
| Sunningdale Developments Limited | Construction | 2007 |
| Sunrise Travel & Tours Limited | Administrative & support | 1991 |
| Support Finance Limited | Professional & scientific | 2006 |
| Support Revolution Holdings Limited | Professional & scientific | 1989 |
| Sure Communication (Sur.Co.Uk) Limited | Information & communication | 2001 |
| Sustain ICT Consultancy Limited | Information & communication | 2012 |
| Swanlink Limited | Financial services | 1998 |
| Sweaty Bums Ltd | Arts & recreation | 2024 |
| Swerve Consulting Ltd | Professional & scientific | 2002 |
| Swift Logistic Solutions Limited | Transport & logistics | 2006 |
| Sygenius Limited | Information & communication | 2002 |
| Synchronous Technologies Limited | Information & communication | 1997 |
| Syntaxus Limited | Information & communication | 2018 |
| Syskin Systems Solutions Limited | Information & communication | 1998 |