| September Way (Stanmore) Management Limited | Households | 1981 |
| Seren Consultants Ltd | Professional & scientific | 2008 |
| Seruni Enterprises Limited | Real estate | 1999 |
| Servepace Limited | Real estate | 1994 |
| Setlane Limited | Households | 2000 |
| Setonbridge Limited | Professional & scientific | 2005 |
| Seven Foot Cowboy Jeans Corporation Limited | Wholesale & retail | 2010 |
| Seven Stars Limited | Hospitality | 2000 |
| SFR Photos Ltd | Professional & scientific | 2004 |
| SFX Labs Ltd | Administrative & support | 2008 |
| Sfxmodels Limited | Manufacturing | 2014 |
| SGE Services Limited | Construction | 2005 |
| Sh.Vm Ltd | Construction | 2015 |
| Shaba Poultry Ltd | Real estate | 2001 |
| Shagwell Productions Ltd | Information & communication | 2025 |
| Shah P.J. & Company Limited | Professional & scientific | 1997 |
| Shah Vintage Zone Ltd | Wholesale & retail | 2023 |
| Shamie Ryan Plant Hire Limited | Administrative & support | 2004 |
| Shamin Limited | Professional & scientific | 1998 |
| Shan Express Limited | Wholesale & retail | 2014 |
| Shanmi RAJ Ltd | Real estate | 2021 |
| Shannon Estates Limited | Extraterritorial | 2003 |
| Shanthi Productions Limited | Information & communication | 1992 |
| Shaplan Limited | Financial services | 1999 |
| Sharda Plastchem (UK) Ltd | Wholesale & retail | 1996 |
| Sharell Ltd | Real estate | 2010 |
| Sharp International Finance (U.K.) PLC | Financial services | 1990 |
| Sharpe Search Limited | Administrative & support | 2025 |
| Sharpton Services Limited | Information & communication | 2006 |
| Shaw Spencer International Group Limited | Real estate | 1994 |
| Shaw Spencer Limited | Real estate | 1993 |
| Shaw Spencer Property Management Limited | Other services | 1972 |
| Shayle Property Company Limited | Real estate | 1968 |
| Sheikh & Co Accountants Limited | Professional & scientific | 2005 |
| Shephard Travis Textile Conservation Studio Limited | Arts & recreation | 2004 |
| Shepherds Hill Land Power Limited | Extraterritorial | 1997 |
| Shepperton Hotels Holdings Limited | Hospitality | 1997 |
| Sherwood Close (Phase 3) Management Company Limited | Real estate | 2024 |
| Sherwood Ventures Limited | Real estate | 2006 |
| Sherwoods Independent Estate Agents Limited | Real estate | 2002 |
| Sheryar N Co. Limited | Wholesale & retail | 2025 |
| SHI International Limited | Wholesale & retail | 2006 |
| Shibren Ltd | Construction | 2007 |
| Shield Insurance Brokers (London) Ltd | Financial services | 2003 |
| Shimpack Engineering (UK) Limited | Manufacturing | 2002 |
| Shinfield (6) Management Limited | Households | 2002 |
| Shipton & Heneage Limited | Wholesale & retail | 1988 |
| Shirbel Investments Limited | Real estate | 1962 |
| Shire Electrical Contractors Ltd | Construction | 2022 |
| Shirehall Limited | Real estate | 1984 |
| Shiva's Cobra Ltd | Real estate | 2004 |
| Shivan Construction Limited | Construction | 2003 |
| Shivansh Enterprise Ltd | Hospitality | 2022 |
| Shiver Ice (UK) Ltd | Manufacturing | 2007 |
| Shivkrupa Food Ltd | Hospitality | 2025 |
| Shonky Pictures Ltd | Information & communication | 2025 |
| Shoppers Stop Limited | Wholesale & retail | 2003 |
| Shore Close Residents Company Limited | Households | 2000 |
| Short Sighted Limited | Arts & recreation | 2010 |
| Short-Term Professional Solutions Ltd. | Professional & scientific | 2001 |
| Shreebai Welfare Foundation (UK) | Other services | 2004 |
| Shreyas S.A.I.N Ltd | Administrative & support | 2005 |
| Shya's Properties Ltd | Real estate | 2021 |
| SI Property Consultants Limited | Professional & scientific | 2004 |
| Siam Ease Limited | Professional & scientific | 2001 |
| Sibthorp Limited | Wholesale & retail | 2023 |
| Sidonsound Limited | Real estate | 1981 |
| Sifran Custom Ltd | Manufacturing | 2005 |
| Sightpath Limited | Professional & scientific | 1999 |
| Sigi Consulting Ltd | Professional & scientific | 2018 |
| Sigma Interactive Solutions Limited | Professional & scientific | 2005 |
| Sikh Warriors Akhara Ltd | Other services | 2017 |
| Silk Touch Limited | Administrative & support | 2005 |
| Silver 6 Ltd | Wholesale & retail | 2006 |
| Silver Rose Limited | Real estate | 2002 |
| Silverberry Capital Limited | Administrative & support | 2021 |
| Silverdale Park Management Company Limited(The) | Households | 1980 |
| Silverhead Services Ltd | Information & communication | 2006 |
| Silverman's Limited | Wholesale & retail | 1946 |
| Silverstone South Management Ltd | Real estate | 2020 |
| SIM Consultancy Ltd | Information & communication | 2015 |
| Simone Fiege - Creative Retouching Limited | Arts & recreation | 2014 |
| Simply Beautiful Hair Limited | Other services | 2007 |
| Simply Carehome Limited | Health & social care | 2008 |
| Simply Software (UK) Limited | Information & communication | 1999 |
| Sims Opticians Limited | Health & social care | 2005 |
| Singam Properties Limited | Real estate | 2017 |
| Singedge Property Management Company Limited | Real estate | 1995 |
| Singh Sabha Sports Club (Southall) Limited | Arts & recreation | 2006 |
| Single Point Financial Services Limited | Financial services | 2007 |
| Sinitron (U.K.) Limited | Transport & logistics | 1978 |
| Sinusoid Consultants Limited | Information & communication | 1990 |
| SIR AP Stewart Limited | Arts & recreation | 2019 |
| Siraji Ltd | Transport & logistics | 2019 |
| Sirichyk Ltd | Health & social care | 2022 |
| SIS Property Investment Limited | Real estate | 2005 |
| Situls (Bedford) Limited | Real estate | 1979 |
| Sivas Construction Ltd | Construction | 2005 |
| SJ Radiology Limited | Professional & scientific | 2019 |
| SJS Accountancy Limited | Professional & scientific | 2005 |