| SES Medical Ltd | Health & social care | 2017 |
| Sevenplatform VI Limited | Financial services | 2021 |
| SG Jagger & Sons Limited | Real estate | 2021 |
| SGM Associates Limited | Other services | 2001 |
| Shafier Estates Limited | Construction | 1997 |
| Shantock Nurseries Limited | Wholesale & retail | 2007 |
| Shara Engineering Consultants Ltd | Construction | 2020 |
| Shared Spaces Limited | Information & communication | 2005 |
| Sharp Solutions Limited | Information & communication | 1995 |
| Sharpblade Limited | Professional & scientific | 2004 |
| Sharpe Property Lets Ltd | Real estate | 2025 |
| Shaw Investments Limited | Real estate | 2001 |
| Shebana Foundation | Administrative & support | 2006 |
| Shield Batteries Limited | Manufacturing | 1973 |
| Shield Battery Services Limited | Water & waste | 1983 |
| Shield Holdings UK Limited | Financial services | 1990 |
| Shinedean Limited | Professional & scientific | 1998 |
| Shiney Box Productions Limited | Construction | 2007 |
| Shoba's Dermacare Ltd | Health & social care | 2025 |
| Shoosh Entertainments Limited | Arts & recreation | 2005 |
| Shopfittings Online Limited | Extraterritorial | 1999 |
| Shoreditch Park Property Ltd | Real estate | 2011 |
| Shorelink (International) Limited | Manufacturing | 1996 |
| Showmobile Services Limited | Administrative & support | 2002 |
| Shredx Limited | Extraterritorial | 2007 |
| SI Properties & Investment Ltd | Real estate | 2020 |
| Sick (UK) Ltd. | Manufacturing | 1973 |
| Sigcare Limited | Wholesale & retail | 2008 |
| Signs and Designs Limited | Manufacturing | 1997 |
| Sikh Education 'Council' Limited | Health & social care | 1989 |
| Silkroad E-Trading Ltd | Wholesale & retail | 2021 |
| Sillwood Solutions Limited | Agriculture & fishing | 2007 |
| Silver Rock Management Group Ltd | Other services | 2025 |
| Silverback Supplements Ltd | Wholesale & retail | 2021 |
| Silverstream Engineering Limited | Manufacturing | 1996 |
| Simon Light Limited | Wholesale & retail | 1993 |
| Simon Shneerson Limited | Professional & scientific | 2003 |
| Simon Wood Limited | Information & communication | 2003 |
| Simplify Construction Ltd | Construction | 2019 |
| Simplify Property Ltd | Real estate | 2018 |
| Singer Owners Club Limited | Other services | 1980 |
| Single Order Source Limited | Professional & scientific | 2001 |
| Site,Secure,Fire & Security Limited | Construction | 2018 |
| SIX PT Limited | Real estate | 1998 |
| SJ AI Consultancy Ltd | Information & communication | 2025 |
| SJ Poulter Building Services Limited | Construction | 2004 |
| Skillmaster Building Limited | Construction | 2001 |
| Skillmaster Limited | Construction | 1996 |
| Skin Beautiful Hertfordshire Limited | Other services | 2024 |
| Skye Developers Limited | Construction | 2006 |
| Skylight Elstree Limited | Hospitality | 2023 |
| Sloane Curtis Interiors Ltd | Construction | 2015 |
| Smart Consultancy Limited | Professional & scientific | 1995 |
| Smartic Limited | Financial services | 2001 |
| SMC Refurbishments Limited | Construction | 2004 |
| Smcl Management Ltd | Construction | 2024 |
| Smithstead Properties Limited | Real estate | 2006 |
| Smokey Benjamin Limited | Professional & scientific | 2006 |
| SMR Dentistry Limited | Health & social care | 2019 |
| Soba Limited | Arts & recreation | 2021 |
| Social Work Placements Limited | Professional & scientific | 2002 |
| Socio Group Ltd | Professional & scientific | 2024 |
| Softrol Systems Ltd | Wholesale & retail | 2000 |
| Solarprobe Limited | Professional & scientific | 2001 |
| Solent Sail Ltd | Transport & logistics | 1993 |
| Solomon Upholstery Ltd | Wholesale & retail | 2024 |
| Soluro Ltd | Construction | 2006 |
| Sonink Limited | Professional & scientific | 1997 |
| Sopwell Clinic Limited | Health & social care | 2002 |
| SOUL6 Limited | Wholesale & retail | 2019 |
| Sound Box Creations Limited | Manufacturing | 2005 |
| Sourdough Sophia Crouch END Ltd | Wholesale & retail | 2025 |
| Sourdough Sophia Hampstead Ltd | Wholesale & retail | 2025 |
| Sourdough Sophia Highgate Ltd | Wholesale & retail | 2025 |
| South Hill Centre | Education | 2004 |
| Southern Counties Finance Limited | Financial services | 1997 |
| Southern Soft Limited | Information & communication | 2014 |
| Southwater Building Company Limited | Construction | 1997 |
| Sov.Ren & Company Limited | Real estate | 2021 |
| Sovereign Car Park Limited | Other services | 1993 |
| Sovereign Cleaning Services Ltd | Administrative & support | 2020 |
| Sovereign Park M.C. Limited | Households | 1987 |
| Spacetech Limited | Wholesale & retail | 2005 |
| Spark and Spell Limited | Wholesale & retail | 2025 |
| Sparklight Limited | Real estate | 1987 |
| Specialised Panel Products Limited | Wholesale & retail | 1998 |
| Spice Harbour Ltd | Hospitality | 2025 |
| Spicebox Express Ltd | Hospitality | 2025 |
| Spider Consultants Limited | Professional & scientific | 2004 |
| Spizzico Restaurant Limited | Hospitality | 1999 |
| Sportiveuk Limited | Arts & recreation | 2013 |
| Sports Therapy UK Ltd. | Education | 2001 |
| Spring Petroleum Company Ltd | Wholesale & retail | 2001 |
| SPW UK Holdings Limited | Financial services | 2024 |
| SR Waverley Ltd | Wholesale & retail | 2024 |
| SRA Capital Ltd | Financial services | 2019 |
| SRG Newmans Limited | Professional & scientific | 2002 |
| SRH Consulting Ltd | Information & communication | 2005 |
| SRP Engineering Limited | Manufacturing | 1998 |
| ST Agnells Farm Residents Company Limited | Households | 1997 |