| Soriso DM Ltd | Administrative & support | 2023 |
| Soriso Enterprises Ltd | Administrative & support | 2020 |
| Soroban Black Limited | Financial services | 2026 |
| Sorof Ltd | Professional & scientific | 2007 |
| Sorrento Management Consultancy Ltd | Professional & scientific | 2013 |
| Sorvio Group Limited | Financial services | 2025 |
| Sosher Media Ltd | Professional & scientific | 2023 |
| Sosteff Properties Ltd | Real estate | 2018 |
| Souli Construction Ltd | Construction | 2022 |
| Soulspire Fitness and Dance Limited | Extraterritorial | 2020 |
| Sound Travel Group Limited | Administrative & support | 2017 |
| Sourced Components (Europe) Ltd | Wholesale & retail | 2014 |
| South Coast Leisure Ltd | Construction | 2004 |
| South Coast Organs Ltd | Other services | 2018 |
| South Island Estates Limited | Professional & scientific | 2016 |
| South MH Services Ltd | Health & social care | 2024 |
| South Plant Services Limited | Construction | 2023 |
| South Property Investment Ltd | Real estate | 2004 |
| South Teach Limited | Other services | 2023 |
| South Wales Alloys Ltd | Manufacturing | 2022 |
| South Wales Builders Ltd | Construction | 2021 |
| South Wales Building and Construction Limited | Construction | 2010 |
| South Wales Chamber of Commerce, Enterprise and Industry Limited | Administrative & support | 1982 |
| South Wales Chauffeurs Ltd | Transport & logistics | 2022 |
| South Wales Enterprises Ltd | Hospitality | 2019 |
| South Wales Exports Limited | Wholesale & retail | 2017 |
| South Wales Fabrics Limited | Administrative & support | 2016 |
| South Wales Flyers Limited | Transport & logistics | 2017 |
| South Wales Heating Limited | Construction | 2020 |
| South Wales Holdings Ltd | Real estate | 2022 |
| South Wales Irrigation Ltd | Manufacturing | 2023 |
| South Wales Maintenance and Engineering Limited | Manufacturing | 2006 |
| South Wales Motor Company Limited | Wholesale & retail | 2007 |
| South Wales Print Ltd | Manufacturing | 2023 |
| South Wales Print Services Limited | Extraterritorial | 2010 |
| South Wales Property Pros Ltd | Administrative & support | 2025 |
| South Wales Property Services Limited | Real estate | 2001 |
| South Wales Props Holdings Limited | Financial services | 2013 |
| South Wales Propshafts Ltd | Wholesale & retail | 2008 |
| South Wales Rendering Ltd | Construction | 2020 |
| South Wales Roofing Ltd | Construction | 2023 |
| South Wales Travel Services Ltd | Transport & logistics | 2025 |
| South Wales Turf and Top Soil Ltd | Wholesale & retail | 2011 |
| South Wales Utility Mapping Limited | Construction | 2017 |
| South Wales Vendz Ltd | Hospitality | 2023 |
| South West and South Wales Garden Furniture Ltd | Wholesale & retail | 2022 |
| South West Loaders Limited | Construction | 2022 |
| South West Maintenance Services Limited | Construction | 2008 |
| South West Pipelines Limited | Construction | 2010 |
| South Western Tubes Limited | Construction | 1981 |
| Southern Home Care Limited | Health & social care | 2018 |
| Southern TRY Management Ltd | Real estate | 2014 |
| Southlakesliveco Ltd | Arts & recreation | 2025 |
| Southward Solutions Ltd | Education | 1996 |
| Southwest Legal Training Limited | Other services | 2019 |
| SP Bb&H Limited | Wholesale & retail | 2000 |
| SP Silksigns Ltd | Professional & scientific | 2026 |
| Spa Technical Writing Ltd | Professional & scientific | 2011 |
| Spacecraft Projects Limited | Construction | 2023 |
| Spark Creative Group Ltd | Hospitality | 2025 |
| Sparkle (South Wales) | Hospitality | 2001 |
| Sparkle Clean & Services Ltd | Administrative & support | 2023 |
| Sparkle Cleaning (South Wales) Ltd | Administrative & support | 2022 |
| Sparkle Tots Day Nursery Ltd | Health & social care | 2025 |
| Sparkling by Beto Ltd | Administrative & support | 2024 |
| Sparkz Installations Limited | Energy | 2007 |
| Spartacus Recovery Limited | Other services | 2020 |
| Spearywell Holdings Limited | Professional & scientific | 2026 |
| Specialeyes Limited | Wholesale & retail | 2023 |
| Specialised Safety and Fire Consulting Ltd | Professional & scientific | 2023 |
| Specialist Building Consultancy Limited | Professional & scientific | 2023 |
| Specialist Electrical Services Limited | Construction | 2018 |
| Specialist Property Group Ltd | Water & waste | 2023 |
| Specto BX Ltd | Wholesale & retail | 2025 |
| Specto TC Limited | Wholesale & retail | 2026 |
| Spectresoft Ltd | Information & communication | 2021 |
| Spectrum Agape Ltd | Manufacturing | 2022 |
| Spectrum Architectural Glazing Holdings Limited | Financial services | 2020 |
| Spectrum Architectural Glazing Limited | Manufacturing | 2013 |
| Spectrum Art Design Limited | Manufacturing | 1999 |
| Speedy James Limited | Transport & logistics | 2025 |
| Speegra Limited | Information & communication | 2009 |
| Spencer Park Management Company (IW) Limited | Households | 2021 |
| Spencers Soft Furnishings Ltd | Manufacturing | 2020 |
| Spesh Event & Party Hire Limited | Hospitality | 2022 |
| SPI Care Ltd | Administrative & support | 2023 |
| Spice and Rice IOW Ltd | Wholesale & retail | 2025 |
| Spice of India (IW) Limited | Hospitality | 2022 |
| Spice R US Ltd | Wholesale & retail | 2024 |
| SPICE16 Ltd | Hospitality | 2026 |
| Spiced OUT Ltd | Transport & logistics | 2017 |
| Spices (Aber) Limited | Hospitality | 2018 |
| Spidee Consultants Ltd | Professional & scientific | 2024 |
| Spidee Property Management Ltd | Households | 2025 |
| Spiller Builders Ltd | Construction | 2026 |
| Spin Restaurants Limited | Hospitality | 2003 |
| Spin Restaurants Wales Limited | Hospitality | 2008 |
| Spinal Neurosurgery Limited | Health & social care | 2016 |
| Spirafix Limited | Manufacturing | 1992 |
| Spirit of Air Limited | Wholesale & retail | 1996 |