| Star Street Music Limited | Information & communication | 1999 |
| Starr Sales Limited | Wholesale & retail | 2025 |
| Stayfluence Ltd | Professional & scientific | 2025 |
| Stellar Roofing and Building Ltd | Construction | 2021 |
| Stem Aesthetics Limited | Manufacturing | 2024 |
| Steper Productions Limited | Information & communication | 2023 |
| Stephanie Jones Limited | Professional & scientific | 2020 |
| Stephen Howarth Consultancy Limited | Professional & scientific | 2025 |
| Stephen J. Woodward Surveyors Limited | Professional & scientific | 2000 |
| Sterling AS Ltd | Health & social care | 2021 |
| Sterling Coffee Co Limited | Hospitality | 2016 |
| Sterling Sourcing Limited | Information & communication | 2008 |
| Sterndale Systems Limited | Real estate | 1992 |
| Stills Photography Limited | Other services | 2005 |
| Stine Goya UK Ltd | Wholesale & retail | 2022 |
| STN Decor Ltd | Construction | 2016 |
| Stoney-Cam a RTM Company Limited | Households | 2020 |
| Stoney-Cam B RTM Company Limited | Households | 2020 |
| Stoney-Cam CD RTM Company Limited | Households | 2020 |
| Storm Publishing Ltd | Information & communication | 2022 |
| Straight to the Point - Cleaning, Building and Maintenance LLP | | 2018 |
| Strange Light Pictures Ltd | Information & communication | 2026 |
| Strategy Consulting Group Limited | Information & communication | 2014 |
| Stretch IT Consulting Limited | Information & communication | 2012 |
| Studio 3 Ltd | Arts & recreation | 2003 |
| Studio Alpa Limited | Professional & scientific | 2019 |
| Studio Dari Ltd | Information & communication | 2022 |
| Studio in Bloom Limited | Wholesale & retail | 2020 |
| Stus Scrap Collection Limited | Water & waste | 2021 |
| Stylemyspace Interiors Ltd | Manufacturing | 2019 |
| Stylian International Investment Group Ltd | Financial services | 2018 |
| SUE Middleton Coaching Ltd | Other services | 2023 |
| Sullivan & Petters Ltd | Professional & scientific | 2019 |
| Sultip Ltd | Professional & scientific | 2012 |
| Summa Group Limited | Professional & scientific | 2017 |
| Summers Securities Limited | Construction | 1965 |
| Summiteer Media Ltd | Professional & scientific | 2025 |
| Summun Limited | Real estate | 2015 |
| Sun Roof Limited | Energy | 2010 |
| Sunbird Technologies Ltd | Information & communication | 2024 |
| Sunrise to Sunset Ltd | Professional & scientific | 2021 |
| Supercool Locations Limited | Professional & scientific | 2013 |
| Supero Executive Coaching Ltd | Professional & scientific | 2024 |
| Superspeed Fashion Belts Limited | Manufacturing | 1980 |
| Surefire Consulting Limited | Information & communication | 2016 |
| Surrey Downs Homecare Ltd | Health & social care | 2022 |
| Surya Associates Ltd | Information & communication | 2013 |
| Surya Trading Ltd | Wholesale & retail | 2026 |
| Susana Smith Designs Ltd | Administrative & support | 2021 |
| Sustainable Future for ALL Ltd | Professional & scientific | 2018 |
| Sustainable Three Rivers CIC | Information & communication | 2022 |
| Svarloka Holdings Ltd | Real estate | 2016 |
| Svkb Limited | Administrative & support | 2025 |
| Svks Properties Limited | Real estate | 2021 |
| SW Geophysics Limited | Professional & scientific | 2021 |
| SW Herts Community Transport Scheme | Other services | 2001 |
| SW London Trades Ltd | Extraterritorial | 2024 |
| Swakeleys Freehold Limited | Real estate | 2024 |
| Swakeleys Property Developments Limited | Real estate | 2021 |
| Swanky Design & Development Limited | Professional & scientific | 2018 |
| Swappit Ltd | Information & communication | 2025 |
| Swasti Real Estate Group Ltd | Real estate | 2021 |
| Sweethay Holdings Ltd | Financial services | 2019 |
| Swimfarms Limited | Education | 2004 |
| Swiss Windows Ltd | Administrative & support | 2022 |
| SY Private Limited | Real estate | 2025 |
| Sycamore Road Flats Limited | Households | 1998 |
| Symbiosis Care Limited | Health & social care | 2019 |
| Synapses Advisory UK Limited | Professional & scientific | 2016 |
| Synaptium Ltd | Information & communication | 2026 |
| Synthesis Leadership Coaching Limited | Professional & scientific | 2017 |
| Sysygy Ltd | Information & communication | 2014 |
| T L Security Ltd | Administrative & support | 2025 |
| T Lane Limited | Real estate | 2012 |
| T&E Consultancy Ltd | Professional & scientific | 2022 |
| T-Power Solutions Limited | Administrative & support | 2011 |
| T2F Events Ltd | Hospitality | 2019 |
| Tacit Networks, Inc. | | 2004 |
| Tack Construction Limited | Construction | 2019 |
| Tadim Properties Limited | Construction | 2023 |
| Tajk Ltd | Information & communication | 2022 |
| Takeawaze Ltd | Information & communication | 2020 |
| Talent & Brands Limited | Professional & scientific | 2018 |
| Talentbase Group Limited | Administrative & support | 2022 |
| Talentbridge Consultancy Ltd | Professional & scientific | 2025 |
| Talking Stickers Ltd | Manufacturing | 2025 |
| Talking Trauma Ltd | Health & social care | 2023 |
| Tall Persons Club, GB & Ireland | Other services | 2000 |
| Talora Group Limited | Administrative & support | 2025 |
| Tanglin House Limited | Financial services | 2014 |
| Tanton One Limited | Professional & scientific | 2014 |
| Tanton Two Limited | Construction | 2014 |
| Tanworth Consulting Services Limited | Health & social care | 2023 |
| Tap'D Solutions Limited | Information & communication | 2015 |
| Tara Coles Ltd | Professional & scientific | 2025 |
| Taravera BIO Limited | Professional & scientific | 2026 |
| Target Graphics Ltd | Arts & recreation | 2012 |
| Tarrattarrat Ltd | Hospitality | 2017 |
| TAS INT Limited | Hospitality | 2018 |
| Tasty Food Solutions Limited | Hospitality | 2016 |