| Seefin Properties Limited | Construction | 2023 |
| Seeta Glamorous Products Ltd | Wholesale & retail | 2023 |
| Seeta Investments Ltd | Real estate | 2015 |
| Selecta JOB Limited | Administrative & support | 2021 |
| Semaphore Holdings Limited | Financial services | 2024 |
| Semaphore Partnership Limited | Information & communication | 1997 |
| Shanagh Properties Limited | Real estate | 1957 |
| Shanlee Limited | Transport & logistics | 2023 |
| Sharontattan Ltd | Education | 2022 |
| Sharvit Productions & Services Ltd | Information & communication | 2021 |
| Shear Rock Limited | Manufacturing | 2021 |
| Sheepstile Ltd | Real estate | 2021 |
| Shehab London Ltd | Administrative & support | 2014 |
| Shellsim Limited | Financial services | 2023 |
| Shenley Equestrian Ltd | Arts & recreation | 2019 |
| Shenley Hill Ltd | Construction | 2021 |
| Shenley Mansion Management Limited | Administrative & support | 1997 |
| Shenley Park Trust | Arts & recreation | 1990 |
| Shmeisenberg Limited | Financial services | 2019 |
| Shosha Ltd | Professional & scientific | 2023 |
| Showstoppers Camp Ltd | Arts & recreation | 2018 |
| Showstoppers HQ Ltd | Arts & recreation | 2023 |
| Sidco Property Ltd | Real estate | 2026 |
| Sidney JAY Properties Ltd | Real estate | 2024 |
| Sifnos Events UK Ltd | Hospitality | 2024 |
| Silogram Consulting Ltd | Professional & scientific | 2014 |
| Simple Network Media Ltd | Information & communication | 2022 |
| Simple Payroll Services Limited | Administrative & support | 2012 |
| Simshell Limited | Real estate | 2011 |
| Sinuosity Ltd | Information & communication | 2018 |
| SIR Patrika Ban-Helda Limited | Wholesale & retail | 1998 |
| Siraya Ltd | Wholesale & retail | 2024 |
| Sirius Legal Limited | Professional & scientific | 2012 |
| Sisco Foods Ltd | Wholesale & retail | 2019 |
| SJC Finance Team Ltd | Professional & scientific | 2012 |
| Skann Ltd | Health & social care | 2025 |
| Skillo Limited | Information & communication | 2017 |
| Skon Spa Limited | Other services | 2017 |
| Skye Care Aviation Ltd | Administrative & support | 2025 |
| Skylortech Limited | Information & communication | 2024 |
| SL Capital Ventures Ltd | Professional & scientific | 2026 |
| Slabgo Ltd | Manufacturing | 2024 |
| Slipalert LLP | | 2003 |
| Smart ITC Limited | Manufacturing | 2016 |
| Smartdental IT Solutions Ltd | Information & communication | 2024 |
| SMK Window Cleaning Ltd | Administrative & support | 2019 |
| Smtrd Ltd | Wholesale & retail | 2023 |
| Snikrep Limited | Mining & quarrying | 2013 |
| Soko & Co Business Finance Ltd | Professional & scientific | 2026 |
| Solid Renewables Limited | Construction | 2014 |
| Solispath Ltd | Information & communication | 2025 |
| Sontrad International Limited | Wholesale & retail | 2023 |
| Sophia Bidco Limited | Financial services | 2023 |
| Sophia Topco Limited | Financial services | 2023 |
| SOS Bookkeeping Services Limited | Professional & scientific | 2015 |
| South England Football Club Limited | Arts & recreation | 2024 |
| Sovritage Ltd | Transport & logistics | 2026 |
| SP Live Ltd | Health & social care | 2021 |
| Special Driver Ltd | Transport & logistics | 2019 |
| Specialist Pension Services Limited | Financial services | 1992 |
| SPS Conferences Limited | Extraterritorial | 2012 |
| SQ Properties (30 Muirkirk Road) Limited | Real estate | 2004 |
| SRT Medical Ltd | Health & social care | 2020 |
| SSC Consultancy Ltd | Professional & scientific | 2023 |
| ST Albans Hockey Club Limited | Arts & recreation | 2008 |
| ST Associate Limited | Professional & scientific | 2008 |
| ST Nicholas Church Fund Great Munden | Education | 1995 |
| ST Smiles Limited | Professional & scientific | 2019 |
| ST. Giles Residents NO.2 Limited | Households | 1997 |
| Stan Transport (UK) Limited | Transport & logistics | 2014 |
| Starline Property Ventures Limited | Real estate | 2010 |
| Starmaker Performing Arts Limited | Arts & recreation | 2012 |
| Steeda UK Limited | Other services | 2012 |
| Stellar Protection Ltd | Financial services | 2019 |
| Stephanie Sollosi Consulting Ltd | Administrative & support | 2008 |
| Stephen Starr Limited | Professional & scientific | 2010 |
| Stern Wind Limited | Energy | 2011 |
| Stonerock Capital Ltd | Construction | 2024 |
| Strata Property Limited | Construction | 2026 |
| Streamito Limited | Information & communication | 2023 |
| Strictly Limited | Professional & scientific | 2025 |
| Stuart Freeman Properties Limited | Real estate | 2018 |
| Studio Beechwood Ltd | Other services | 2025 |
| Studioryko Ltd | Professional & scientific | 2014 |
| Style Kitchens Limited | Wholesale & retail | 2008 |
| SU Kaye Photography Limited | Professional & scientific | 2008 |
| SUB Call Ltd | Administrative & support | 2025 |
| Sumaria Surgery Limited | Health & social care | 2019 |
| Sunrish Enterprises Limited | Financial services | 2020 |
| Sunshine Accounting Limited | Professional & scientific | 2016 |
| Supersteel Construction Ltd | Construction | 2024 |
| Sustainants Limited | Professional & scientific | 2025 |
| Sutaka UK Limited | Wholesale & retail | 2010 |
| Swing City Golf & Leisure Limited | Professional & scientific | 2016 |
| Syjor Property Limited | Real estate | 2013 |
| T Ivory Ltd | Wholesale & retail | 2025 |
| T M Jones Properties Limited | Construction | 2015 |
| T.I.J. Properties Limited | Construction | 1961 |
| Tachomate Limited | Wholesale & retail | 2017 |
| TAI CHI Supplies Limited | Extraterritorial | 2017 |