| Sparkle Dental Staff Ltd | Health & social care | 2019 |
| Sparks MK Ltd | Construction | 2024 |
| Sparktangent Limited | Professional & scientific | 2012 |
| Sparrows Care Ltd | Health & social care | 2016 |
| Spartan Steels Limited | Wholesale & retail | 2003 |
| SPC Heating & Plumbing Limited | Construction | 2021 |
| Special Branch Tree Surgeons Maidenhead Ltd | Administrative & support | 2019 |
| Special Gift Cards Limited | Information & communication | 2022 |
| Specialist Moves and Installations Limited | Transport & logistics | 2005 |
| Spectra Design Ltd | Real estate | 2025 |
| Spectrum International Consultants Ltd | Professional & scientific | 2026 |
| Spektor Limited | Professional & scientific | 2016 |
| Spelina Real Estate Limited | Real estate | 2024 |
| Spencers Road IT Ltd | Information & communication | 2015 |
| Spendlink Limited | Information & communication | 2008 |
| SPG Media Limited | Information & communication | 2020 |
| SPH Eyecare Limited | Health & social care | 2011 |
| Spica Logistics Limited | Transport & logistics | 2019 |
| Spicy Taste Fusion Ltd | Hospitality | 2025 |
| Spike Reports Ltd | Health & social care | 2020 |
| SPK Solutions Limited | Information & communication | 2015 |
| Splashy FEN Properties Ltd | Real estate | 2019 |
| Splice Comm Ltd | Information & communication | 2009 |
| Split Properties Limited | Real estate | 2007 |
| Spoormaker & Partners Global Ltd | Professional & scientific | 2024 |
| Spoormaker & Partners UK Ltd | Professional & scientific | 2019 |
| Spor Group Limited | Construction | 2019 |
| Sport Design Sweden Limited | Manufacturing | 2021 |
| Spotted Waves Ltd | Wholesale & retail | 2025 |
| Springbucks Gymnastics Club Limited | Education | 2014 |
| Springfield Health Services Limited | Health & social care | 2001 |
| Sprinkles and Sparkles Ltd | Arts & recreation | 2013 |
| Sprint Business Consulting Limited | Information & communication | 2013 |
| Sprint Management Limited | Real estate | 2019 |
| Spritz Marketing & PR Limited | Professional & scientific | 2014 |
| Sprout Studio Ltd | Professional & scientific | 2026 |
| Sprung Collective Limited | Professional & scientific | 2021 |
| SPT Carpentry Services Limited | Construction | 2003 |
| SQ Corporation Limited | Professional & scientific | 1994 |
| SQ Finance NO 2 Limited | Financial services | 1993 |
| Square Creative Limited | Information & communication | 2023 |
| Square Roots Partners Limited | Other services | 2013 |
| Square Socket Limited | Professional & scientific | 2013 |
| Squared UP Holdings Limited | Financial services | 2018 |
| Squared UP Ltd | Information & communication | 2011 |
| Squires Executive Limited | Transport & logistics | 1993 |
| SR Lavatory Ltd | Professional & scientific | 2025 |
| Sreehan Limited | Information & communication | 2025 |
| SRG Sidhu Ltd | Real estate | 2017 |
| SRI Datta SAI Limited | Information & communication | 2014 |
| SRI Planning & Engineering Services Limited | Professional & scientific | 2021 |
| SRI Prathinik Consulting Limited | Information & communication | 2013 |
| Sribes Life Sciences Ltd | Professional & scientific | 2026 |
| SRL Marketing Limited | Professional & scientific | 2007 |
| SRQ Technology Ltd | Information & communication | 2025 |
| SRS Holdings (High Wycombe) Limited | Financial services | 2024 |
| Srss Heating Ltd | Construction | 2020 |
| SSD Contractors Ltd | Construction | 2017 |
| SSD Pharma Limited | Administrative & support | 2021 |
| SSD Pharma Services Ltd | Professional & scientific | 2024 |
| Ssed Ltd | Wholesale & retail | 2003 |
| SSJ Technik Ltd | Manufacturing | 2024 |
| SSS and Sons Ltd | Wholesale & retail | 2012 |
| Sstyal Ltd | Extraterritorial | 2019 |
| ST John Homes (Thames Valley) Ltd | Construction | 2016 |
| ST Matthews Court (Alwyn Road) Residents Management Company Limited | Households | 2010 |
| ST Nicolas' CE Combined School Taplow | Education | 2012 |
| ST8TMENT Limited | Construction | 2024 |
| Stable Arch Advisory Limited | Professional & scientific | 2026 |
| Stacey Hydramech Limited | Manufacturing | 1996 |
| Stacks Property Search South Bucks Limited | Professional & scientific | 2026 |
| Stake Boat Properties Limited | Construction | 2016 |
| Stallion Tyres and Recovery Ltd | Wholesale & retail | 2025 |
| Stanley Peake & SON Limited | Wholesale & retail | 1962 |
| Stardust Brewery Ltd | Manufacturing | 2016 |
| Starfish Accounting Ltd | Professional & scientific | 2011 |
| Starhouse Trading Group Ltd | Wholesale & retail | 2020 |
| Stars Boutique Ltd | Wholesale & retail | 2024 |
| Started From Scratch Online Marketing Limited | Professional & scientific | 2017 |
| Staxlink Properties Ltd | Construction | 2014 |
| Stay Active Youth Ltd | Arts & recreation | 2023 |
| Steel Brothers and Company Limited | Professional & scientific | 1890 |
| Steelspan Scaffolding Ltd | Construction | 2026 |
| Stella Trade Limited | Transport & logistics | 2020 |
| Stellanto Ltd | Information & communication | 2023 |
| Stennru Ltd | Real estate | 2024 |
| Steph Barber Hospitality Limited | Professional & scientific | 2026 |
| Steph Virtual Assistant Limited | Administrative & support | 2023 |
| Stephanie D Therapy Limited | Health & social care | 2024 |
| Stephen Toulson & Sons Limited | Professional & scientific | 1927 |
| Stepn Ltd | Administrative & support | 2019 |
| Stepping OFF Limited | Arts & recreation | 2022 |
| Sterilex UK Ltd | Manufacturing | 2022 |
| Sterling Ventures London Holdings Limited | Real estate | 2020 |
| Sterling Ventures London Limited | Real estate | 2016 |
| Stessa by Sarah Ltd | Manufacturing | 2024 |
| Steve Johnstone Consulting Limited | Professional & scientific | 2024 |
| Steve's Maintenance Services Ltd | Water & waste | 2009 |
| Stewartby Housing Association Limited | Professional & scientific | 1950 |
| Steyn and Sons Property Services Ltd | Households | 2022 |