| Smoke ME a Kipper Ltd | Information & communication | 2024 |
| Smokey Embers BBQ Ltd | Hospitality | 2021 |
| Smol Hospitality & Property Ltd | Real estate | 2021 |
| Snatch 44 Limited | Hospitality | 2014 |
| Snowdell Farm Management Ltd | Administrative & support | 2026 |
| Snowdrop Events Ltd | Administrative & support | 2019 |
| Software Systems Developments Limited | Manufacturing | 2016 |
| Solec Electrical Ltd | Construction | 2024 |
| Sonnleitn Ltd | Real estate | 2019 |
| Sophia Hutchinson Limited | Professional & scientific | 2023 |
| Sosban Ltd | Hospitality | 2011 |
| Sound Consultants Limited | Professional & scientific | 2012 |
| Sound Consulting Limited | Professional & scientific | 2017 |
| South and West Surveys Ltd | Professional & scientific | 1998 |
| South Lakes Recruitment Ltd | Administrative & support | 2023 |
| Southern P.V.C. Systems Limited | Construction | 1983 |
| Southstreet Farmers Limited | Agriculture & fishing | 1998 |
| Sovereign Food Group Limited | Wholesale & retail | 2025 |
| Spanner Contracting Limited | Professional & scientific | 2024 |
| Sparkle Sisters Jewellery Ltd | Wholesale & retail | 2026 |
| Sparks Pottery by RHI Limited | Manufacturing | 2025 |
| Spearhill Ltd | Real estate | 2026 |
| Spearmarsh Ltd | Wholesale & retail | 2001 |
| Spicers Meat Wagon Ltd | Hospitality | 2017 |
| Spilman Hotel Holdings Ltd | Hospitality | 2022 |
| Spilman Hotel Ltd | Hospitality | 2019 |
| Spine and Sports Physio Ltd | Health & social care | 2006 |
| Spinnaker (Tenby) Limited | Administrative & support | 2020 |
| Sponge Monkeys Ltd | Other services | 2017 |
| Sporting Chance (Red Roses) Limited | Hospitality | 2024 |
| Sports Medicine West Wales Ltd | Health & social care | 2026 |
| Springfield Trading Ltd | Professional & scientific | 2019 |
| Springwater Lakes Ltd. | Arts & recreation | 1998 |
| Sprinkle Farms Limited | Agriculture & fishing | 2002 |
| Sprinkler Pumps UK Ltd | Manufacturing | 2022 |
| Sprite Storm Ltd | Information & communication | 2018 |
| Sproutopia Microgreens Ltd | Wholesale & retail | 2024 |
| Spud Shack Llanelli Limited | Hospitality | 2024 |
| Spy-I Ltd | Real estate | 2006 |
| Squib Properties Ltd | Real estate | 2020 |
| SS Goddard Limited | Construction | 2013 |
| ST Clears Car & Commercial Autopaint and Repair Centre Limited | Wholesale & retail | 2022 |
| ST Davids Diocesan Board of Finance (Property) Limited | Real estate | 2019 |
| St.Davids Diocesan Board of Finance(The) | Other services | 1929 |
| Stacey’S Kitchen Limited | Hospitality | 2022 |
| Stanley Rose Hair Limited | Other services | 2017 |
| Starboard Enterprises PC | | 2018 |
| Starkmorr Construction Limited | Construction | 2024 |
| Start Young Driver Experience Ltd | Education | 2025 |
| Starwell Universal PC | | 2019 |
| Stecam Logistics Limited | Transport & logistics | 2019 |
| Steel Fabricators (Wales) Ltd | Construction | 2007 |
| Steil Pleser Limited | Wholesale & retail | 2002 |
| Stephen T Evans Limited | Administrative & support | 2017 |
| Sterafill Limited | Manufacturing | 2016 |
| Steve Reed & Sons Plant Hire Ltd | Construction | 2026 |
| Steven Rees Wealth Management Limited | Financial services | 2012 |
| Stilemark Trade L.P. | | 2018 |
| Stone Range Brook Limited | Hospitality | 2024 |
| Stone Technology Ltd | Professional & scientific | 2004 |
| Strawberry Shortcake Ltd | Hospitality | 2013 |
| Streamline Contract Services Ltd | Construction | 2021 |
| Strider Sports Limited | Wholesale & retail | 2024 |
| Stuart Lloyd Associates Ltd | Professional & scientific | 2003 |
| Studio Claash Limited | Construction | 2026 |
| Studio Pren Limited | Manufacturing | 2019 |
| Studio Resource Management Limited | Professional & scientific | 2010 |
| Studio REY Ltd | Professional & scientific | 2019 |
| SUE Broad Ltd | Health & social care | 2022 |
| SUE Williams Expert Witness Limited | Professional & scientific | 2016 |
| Sun and Windrose Consulting Limited | Professional & scientific | 2023 |
| Sunflower Lounge Ltd | Health & social care | 2021 |
| Super Duper Decor Limited | Wholesale & retail | 2014 |
| Super Henry Enterprises Limited | Wholesale & retail | 2025 |
| Super Micro Holdings Ltd | Professional & scientific | 2025 |
| Supersport Systems Limited | Information & communication | 2012 |
| Supporters of Nuclear Energy Limited | Other services | 1998 |
| Sushiwales Limited | Hospitality | 2023 |
| Sustainable Honey Bees CIC | Agriculture & fishing | 2024 |
| Sv-En Translations Limited | Professional & scientific | 2008 |
| SVH Solutions Limited | Financial services | 2023 |
| SW EOT Trustee Limited | Professional & scientific | 2026 |
| Swansea Business School Limited | Professional & scientific | 1995 |
| Sweet and Surf Limited | Wholesale & retail | 2018 |
| Swift Cabs Laugharne Limited | Transport & logistics | 2019 |
| Swift Relocations Ltd | Real estate | 2010 |
| Swift Skim Ltd | Construction | 2024 |
| Swnafon Farm Limited | Agriculture & fishing | 2025 |
| Swss Limited | Wholesale & retail | 2003 |
| Sylprin Ltd | Real estate | 2023 |
| Sylvaen CYF | Agriculture & fishing | 2010 |
| Sylwester Construction Ltd | Construction | 2019 |
| Symbiotic Farming Limited | Agriculture & fishing | 2017 |
| Synaptic Bridge Ltd | Information & communication | 2025 |
| Systems Installations (Wales) Limited | Wholesale & retail | 2002 |
| Systemtrading L.P. | | 2018 |
| Szubka Davies Holdings Ltd | Hospitality | 2024 |
| T & C (Holdings) - Tenby Limited | Real estate | 2022 |
| T & R Thomas Properties Limited | Real estate | 2024 |
| T Alun Jones & SON | Wholesale & retail | 2017 |