| Snapkey Car Locksmith Ltd | Wholesale & retail | 2025 |
| Sneezing Giraffe Limited | Information & communication | 2024 |
| Snowdrop Holdings Ltd | Real estate | 2016 |
| SNT Media Group Limited | Information & communication | 2017 |
| Social Synergy Limited | Professional & scientific | 2018 |
| Sofa City Direct Ltd | Manufacturing | 2026 |
| Sofa-Icon Limited | Manufacturing | 2006 |
| Sofaschoice Ltd | Manufacturing | 2021 |
| Soft Landings Play Zone Ltd | Arts & recreation | 2019 |
| SOL Regem Ltd. | Wholesale & retail | 2017 |
| Solar & Energy Solutions (UK) Limited | Professional & scientific | 2020 |
| Solar Energy Farm Ltd | Energy | 2015 |
| Solar Group Holdings Limited | Manufacturing | 2018 |
| Solar Sunshades (UK) Limited | Professional & scientific | 1978 |
| Solar Sunshades Limited | Manufacturing | 1996 |
| Sole Retail Ltd | Wholesale & retail | 2021 |
| Solera Foods Ltd | Hospitality | 2026 |
| Solid Solutions Consultancy Ltd | Extraterritorial | 2023 |
| Solis Eyewear Ltd | Wholesale & retail | 2026 |
| Solo Global Ltd | Information & communication | 2026 |
| Solutions 123 Limited | Education | 2021 |
| Solveit.Technology Limited | Information & communication | 2014 |
| Solvio Limited | Information & communication | 2019 |
| Soma Restore Ltd | Wholesale & retail | 2020 |
| Somers Isles Properties Limited | Real estate | 2017 |
| Songhurst Developments Ltd | Construction | 2021 |
| Sonnekus Ltd | Professional & scientific | 2025 |
| Sony UK Technology Centre Limited | Manufacturing | 2024 |
| Sophie Healthcare Ltd | Health & social care | 2019 |
| Soul & Soma Limited | Other services | 2024 |
| Soul Reaper Film Limited | Information & communication | 2018 |
| Soul Speaks Limited | Information & communication | 2003 |
| Soulful Music Ltd | Wholesale & retail | 2019 |
| South Barn Solutions Limited | Extraterritorial | 2005 |
| South Cornelly Renewable Energy C.I.C. | Other services | 2023 |
| South Eastern Energy Limited | Professional & scientific | 2012 |
| South Wales Accountancy & Taxation Limited | Professional & scientific | 2009 |
| South Wales Accountancy Limited | Professional & scientific | 2012 |
| South Wales Auto Tech Ltd | Wholesale & retail | 2026 |
| South Wales Cladding Ltd | Construction | 2025 |
| South Wales Energy Limited | Extraterritorial | 2012 |
| South Wales Exam Centre Ltd | Education | 2025 |
| South Wales GAS Limited | Professional & scientific | 1997 |
| South Wales Ground Testing Ltd | Construction | 2021 |
| South Wales Insulation Ltd | Construction | 2024 |
| South Western Energy Limited | Mining & quarrying | 2012 |
| Southern Ground Testing Limited | Construction | 2002 |
| Southern View Property Ltd | Real estate | 2018 |
| Southmills Property Ltd | Real estate | 2025 |
| Spannerman Limited | Wholesale & retail | 2023 |
| Sparkle Cleaning Bridgend Ltd | Administrative & support | 2026 |
| Sparrow and SON Waste Removal Limited | Extraterritorial | 2020 |
| Spartan Cork Spray Ltd | Construction | 2022 |
| SPD Consultants (Wales) Ltd | Professional & scientific | 2019 |
| Spear Independent Financial Advice Limited | Financial services | 2017 |
| Specialist Labour Solutions Ltd | Construction | 2023 |
| Speciality, Packaging, Thermoforming Materials Ltd | Manufacturing | 2008 |
| Spectrum Blinds (UK) Limited | Professional & scientific | 2006 |
| Spectrum GEO Services Limited | Professional & scientific | 2019 |
| Spectrum Technologies Limited | Manufacturing | 1989 |
| Spectrum Technologies Profit Sharing Scheme Trustees Limited | Professional & scientific | 1998 |
| Spencer Stone Group Limited | Financial services | 2024 |
| Spencer Stone Properties Ltd | Households | 2024 |
| SPF Construction (Bridgend) Ltd | Construction | 2009 |
| SPH Displays Limited | Administrative & support | 2023 |
| Spice & Street Ltd | Hospitality | 2024 |
| Spicebridge Ltd | Hospitality | 2025 |
| Spjtex AI Limited | Information & communication | 2025 |
| Splice Child and Family Project Limited | Other services | 2006 |
| Spms (Wales) Limited | Construction | 2007 |
| Spoonvfx Ltd | Information & communication | 2022 |
| Spring Design Consultancy (Holdings) Limited | Construction | 2024 |
| Spring Design Consultancy Limited | Construction | 2011 |
| Springstone Software Ltd | Information & communication | 2021 |
| Sprinting Frog Payroll Services Ltd | Administrative & support | 2021 |
| Sprinting Hare JDM Limited | Wholesale & retail | 2014 |
| Spsca Venture Limited | Extraterritorial | 2019 |
| Spwh Ltd | Wholesale & retail | 2026 |
| Square and Compasses Bar Limited | Hospitality | 2013 |
| Squared Accountancy Ltd | Professional & scientific | 2021 |
| Squiggle IT Limited | Information & communication | 2017 |
| SR & Blackwell Ltd | Construction | 2024 |
| SR Bridgend Ltd | Hospitality | 2023 |
| SR Legal Solutions Ltd | Professional & scientific | 2026 |
| SR Pubs Ltd | Hospitality | 2025 |
| SRJ Properties Limited | Construction | 2010 |
| SRK Logistics Ltd | Transport & logistics | 2019 |
| SRM Precision Engineering Limited | Manufacturing | 2002 |
| SRS Electrical Solutions Limited | Extraterritorial | 2019 |
| SRS Support Limited | Information & communication | 2011 |
| ST. John's Priory Management Company Limited | Professional & scientific | 1997 |
| ST. John`S Vision Limited | Administrative & support | 2003 |
| ST. Marys Enterprises Ltd | Wholesale & retail | 2013 |
| Stacks Cafe Limited | Manufacturing | 2025 |
| Stadiwm Energy Ltd | Energy | 2025 |
| Staedtler (U.K.) Limited | Wholesale & retail | 1964 |
| Stairlift Clinic Ltd | Wholesale & retail | 2025 |
| Stansall Limited | Extraterritorial | 2026 |
| Stanslee Limited | Extraterritorial | 2025 |
| Star Care Solutions Limited | Administrative & support | 2023 |