| Softstuff Consulting Ltd | Information & communication | 2016 |
| Softstuff Limited | Information & communication | 2020 |
| Software & Marketing Solution Limited | Information & communication | 2020 |
| Software Links Limited | Information & communication | 2015 |
| Solair Solutions Ltd | Construction | 2022 |
| Solarcentric Renewables Limited | Construction | 2020 |
| Solas Estates Limited | Real estate | 2025 |
| Soleada Escapes Holdings Limited | Financial services | 2023 |
| Solid Fuel Services Limited | Construction | 2001 |
| Solid Partners Limited | Financial services | 2024 |
| Solid Surface Repair Ltd | Other services | 2023 |
| Solidpoint Building Services Ltd | Administrative & support | 2026 |
| Solidstone Builders (Swansea) Ltd | Construction | 2026 |
| Solis Design Ltd | Professional & scientific | 2021 |
| Solo House Ltd | Other services | 2024 |
| Solo Janitorial Supplies Limited | Wholesale & retail | 1996 |
| Solo Laundry and Linen Services Limited | Administrative & support | 1997 |
| Solo Promotions Ltd | Arts & recreation | 2024 |
| Solomon Electrical (Wales) Limited | Manufacturing | 2014 |
| Solomon Investments Limited | Hospitality | 2007 |
| Solomon Property Investments Ltd | Real estate | 2017 |
| Solstace Ltd | Hospitality | 2015 |
| Solutiondx Ltd | Professional & scientific | 2024 |
| Solutions 17 Limited | Administrative & support | 2015 |
| Solva Road Management Company Limited | Households | 2022 |
| SOLVE4X Ltd | Information & communication | 2018 |
| Solvedata 2000 Limited | Information & communication | 1999 |
| Soma Education Ltd | Education | 2018 |
| Soma London England Ltd | Arts & recreation | 2017 |
| Soma Retail Ltd | Wholesale & retail | 2018 |
| Something Different Wholesale Group Limited | Financial services | 2025 |
| Something Different Wholesale Holdings Ltd | Wholesale & retail | 2019 |
| Something Different Wholesale Limited | Wholesale & retail | 2004 |
| Something Different Wholesale Properties Ltd | Administrative & support | 2019 |
| Something Financial Ltd | Professional & scientific | 2015 |
| Something to Grout About Ltd | Construction | 2023 |
| Sona Care Services Limited | Health & social care | 2016 |
| Sonali (Swansea) Limited | Hospitality | 2017 |
| Sondelier Limited | Information & communication | 2021 |
| Songs and Villas Limited | Real estate | 2017 |
| Sonic Frontiers Limited | Professional & scientific | 2019 |
| Sonja Hookway Psychotherapy Ltd | Health & social care | 2020 |
| Sonny Hospitality Ltd | Hospitality | 2025 |
| Soors Ltd | Water & waste | 2010 |
| Sophie Mccormack Consultancy Limited | Financial services | 2023 |
| Sophie Tamara Morris Consultancy Ltd | Professional & scientific | 2021 |
| Sophisticated Savings Ltd | Wholesale & retail | 2024 |
| Sorem Developments Limited | Construction | 1983 |
| Soroni Limited | Information & communication | 2017 |
| Sorted! GAS Ltd | Construction | 2014 |
| SOS Enterprise Group Limited | Information & communication | 2024 |
| SOS Tcps Limited | Professional & scientific | 2025 |
| Soul Fire Project CIC | Agriculture & fishing | 2019 |
| Soulful Sounds and Arts HWB CIC | Education | 2026 |
| Soulis Global Ltd | Wholesale & retail | 2025 |
| Sound Haven Studios Limited | Information & communication | 2023 |
| Soundbarrier Limited | Arts & recreation | 1972 |
| Source for ME Limited | Wholesale & retail | 2006 |
| Source-Re Limited | Professional & scientific | 2021 |
| Sourcebox Ltd | Other services | 2020 |
| South & West Surfacing Ltd | Construction | 2026 |
| South and West Wales Fishing Communities Limited | Agriculture & fishing | 2003 |
| South Coast Houses Limited | Real estate | 2025 |
| South Coast Plumbing & Heating Ltd | Construction | 2012 |
| South Coast Property Maintenance Ltd | Manufacturing | 2024 |
| South Gower Enterprises Limited | Hospitality | 2016 |
| South Gower Rugby Football Club Limited | Arts & recreation | 2016 |
| South Haven Construction Limited | Construction | 1985 |
| South Haven Developments Limited | Extraterritorial | 1992 |
| South India Tours and Travel Limited | Administrative & support | 2017 |
| South Wales 4X4 Ltd | Wholesale & retail | 2023 |
| South Wales Access Hire Ltd | Construction | 2025 |
| South Wales Activities - Bubble Football Ltd | Arts & recreation | 2025 |
| South Wales Adventure Company Ltd | Arts & recreation | 2022 |
| South Wales Amusements Hire Limited | Administrative & support | 2026 |
| South Wales Appliance Repairs Limited | Other services | 2026 |
| South Wales Arborists Ltd | Agriculture & fishing | 2004 |
| South Wales Audio Limited | Arts & recreation | 2016 |
| South Wales Brickwork and Scaffold Limited | Construction | 2016 |
| South Wales Businesses Ltd | Information & communication | 2026 |
| South Wales Car Centre Limited | Wholesale & retail | 2021 |
| South Wales Cladding & Fabrication Ltd | Wholesale & retail | 2025 |
| South Wales Cleaning and Maintenance Limited | Administrative & support | 2015 |
| South Wales Construction & Shop Fitting Limited | Construction | 2016 |
| South Wales Decorators Ltd | Construction | 2013 |
| South Wales Diagnostics Limited | Wholesale & retail | 2025 |
| South Wales Diesel Specialists Limited | Wholesale & retail | 2023 |
| South Wales Diesels Ltd | Wholesale & retail | 2019 |
| South Wales Drains Ltd | Administrative & support | 2025 |
| South Wales Fencing Ltd | Construction | 2009 |
| South Wales GAS and Boiler Services Ltd | Construction | 2026 |
| South Wales GAS Services Ltd | Construction | 2018 |
| South Wales Grocers Ltd | Wholesale & retail | 2022 |
| South Wales Groundworks Limited | Construction | 2026 |
| South Wales Heat Pumps Limited | Construction | 2023 |
| South Wales Hips Ltd | Administrative & support | 2007 |
| South Wales Industrial Valves Services Limited | Manufacturing | 1981 |
| South Wales Leisure Amusements Limited | Arts & recreation | 1978 |
| South Wales Lettings Ltd | Real estate | 2023 |
| South Wales Pest Experts Limited | Agriculture & fishing | 2021 |