| S Morris Electrical Contractor Limited | Construction | 2017 |
| S P (Swansea) Limited | Financial services | 2017 |
| S P Hospitality Limited | Hospitality | 2015 |
| S Pearce Holdings Ltd | Financial services | 2026 |
| S R Cooling Limited | Manufacturing | 2009 |
| S R G Contractors Ltd | Construction | 2013 |
| S R Properties (Swansea) Limited | Real estate | 2008 |
| S S Property Swansea Investment Ltd | Real estate | 2022 |
| S T R Cleaning Limited | Administrative & support | 2013 |
| S Thomas Plumbing & Building Maintenance Ltd | Construction | 2022 |
| S View Hotel Ltd | Hospitality | 2020 |
| S W Heating & Plumbing (Gower) Ltd | Construction | 2014 |
| S&A Swansea Valley Ltd | Financial services | 2025 |
| S&C Pharmacy Services LLP | | 2023 |
| S&J Auto Solutions Ltd | Wholesale & retail | 2025 |
| S&K (Swansea) Limited | Wholesale & retail | 2016 |
| S&K Housewares Ltd | Wholesale & retail | 2023 |
| S&M Kasto Ltd | Real estate | 2021 |
| S&V TCG Limited | Wholesale & retail | 2025 |
| S. C. Topping Ltd | Manufacturing | 2025 |
| S. H. P. Webborn Limited | Health & social care | 2002 |
| S.& a. Stationers Limited | Administrative & support | 2000 |
| S.& W.W.Finance Co.Limited | Financial services | 1958 |
| S.A.3 Cliffs Limited | Real estate | 2003 |
| S.C.U Furniture Ltd | Manufacturing | 2017 |
| S.M.R. (UK) Ltd | Administrative & support | 1999 |
| S.P.G. (Power Machine Services) Limited | Wholesale & retail | 1980 |
| S.V.B. Engineering Ltd | Manufacturing | 2010 |
| S.W Monumental Masons Limited | Manufacturing | 2024 |
| S.W.J Consulting Limited | Information & communication | 1996 |
| S2S Medical Limited | Health & social care | 2022 |
| S4 Stainless Industrial & Marine Limited | Manufacturing | 2024 |
| S4S Maintenance Ltd | Construction | 2016 |
| S52 Services Limited | Construction | 2016 |
| S8080 Limited | Information & communication | 2000 |
| SA & AK Property Management Ltd | Real estate | 2025 |
| SA 1 Pallets Ltd | Water & waste | 2011 |
| SA Cabs Swansea Limited | Transport & logistics | 2025 |
| SA Escape Rooms Ltd | Arts & recreation | 2026 |
| SA Firewood Suppliers Ltd | Wholesale & retail | 2026 |
| SA Healthcare Limited | Administrative & support | 2016 |
| SA Locks Ltd | Wholesale & retail | 2026 |
| SA Logistics Ltd | Transport & logistics | 2019 |
| SA One Healthtech Limited | Professional & scientific | 2007 |
| SA1 Accountancy Services Ltd | Professional & scientific | 2026 |
| SA1 Business Park Limited | Real estate | 2018 |
| SA1 Coffee Limited | Hospitality | 2019 |
| SA1 Colour Press Ltd | Information & communication | 2013 |
| SA1 Creative Limited | Information & communication | 2014 |
| SA1 Electrical Services Ltd | Construction | 2025 |
| SA1 Frozen Foods Limited | Wholesale & retail | 2017 |
| SA1 Grocery (Swansea) Ltd | Wholesale & retail | 2021 |
| SA1 Group Limited | Financial services | 2023 |
| SA1 Healthcare Ltd | Real estate | 2023 |
| SA1 Holding Company Ltd | Administrative & support | 2013 |
| SA1 Hospitality Ltd | Hospitality | 2025 |
| SA1 Management Ltd | Agriculture & fishing | 2023 |
| SA1 MOT Centre Ltd | Wholesale & retail | 2010 |
| SA1 Pizza Ltd | Hospitality | 2025 |
| SA1 Properties Limited | Real estate | 2004 |
| SA1 Property Investments Limited | Real estate | 1945 |
| SA1 Property Maintenance Limited | Administrative & support | 2024 |
| SA1 Removals Ltd | Transport & logistics | 2024 |
| SA1 Roofing & Construction Ltd | Construction | 2023 |
| SA1 Security Ltd | Administrative & support | 2024 |
| SA1 Solutions Limited | Information & communication | 2005 |
| SA1 Telecoms Limited | Information & communication | 2015 |
| SA1 Trade Ltd | Wholesale & retail | 2025 |
| SA1 Tyre Center Limited | Wholesale & retail | 2023 |
| SA11LZA Investments Limited | Financial services | 2026 |
| SA12 Energy Services Ltd | Administrative & support | 2010 |
| SA2 Property and Investments Limited | Real estate | 2021 |
| SA3 Property Holdings Limited | Real estate | 2024 |
| SA5 Group Limited | Transport & logistics | 2021 |
| SA6 Autos Ltd | Wholesale & retail | 2025 |
| SA9 Cars Limited | Transport & logistics | 2018 |
| SA9 Kitchens Ltd | Construction | 2022 |
| SA9 Storage Ltd | Administrative & support | 2018 |
| SA9 Tyres Ltd | Wholesale & retail | 2022 |
| SAB (Wales) Limited | Construction | 2012 |
| SAB Marketing and Investment Ltd | Professional & scientific | 2004 |
| Saba Consult Limited | Professional & scientific | 2004 |
| Sabil Ventures Private Ltd | Extraterritorial | 2025 |
| Sable Hair Limited | Other services | 2026 |
| Sabre Ring Limited | Real estate | 1995 |
| Sacred Rituals Ltd | Health & social care | 2025 |
| Saddleglow Limited | Administrative & support | 1982 |
| Safe Document Storage Ltd | Other services | 2015 |
| Safe GAS Cylinders Limited | Administrative & support | 2009 |
| Safe Haven Finance Ltd | Financial services | 2017 |
| Safe Property Renovations Limited | Construction | 2025 |
| Safe Recycling Limited | Construction | 2023 |
| Safe Roofing Specialists Limited | Construction | 2025 |
| Safe Roost Limited | Real estate | 2015 |
| Safeguard Inspection Services Ltd. | Professional & scientific | 2001 |
| Safeguard Management Consulting Ltd | Professional & scientific | 2024 |
| Safelight Photography Services Limited | Professional & scientific | 2016 |
| Safernest Ltd | Health & social care | 2025 |
| Safetysolutions 2022 Limited | Professional & scientific | 2022 |
| Safeway Scaffolding Solutions Ltd | Construction | 2017 |