| SJC Assets Ltd | Real estate | 2018 |
| Skyward Investments Limited | Real estate | 2003 |
| Slipmoor Property Management Limited | Extraterritorial | 2002 |
| Slo-Mo Events Limited | Professional & scientific | 2019 |
| Smart Trading (Wales) Limited | Wholesale & retail | 2008 |
| SME Equity Partners Limited | Professional & scientific | 2026 |
| SME Partners Group Ltd | Financial services | 2024 |
| Smfi Limited | Manufacturing | 2009 |
| Smokehouse Gold Limited | Manufacturing | 2020 |
| Smoochies Limited | Wholesale & retail | 2021 |
| Smugglers Retreat Management Company Limited | Real estate | 2009 |
| Snapdragonz Limited | Administrative & support | 2019 |
| SO What ERA Ltd | Health & social care | 2025 |
| Social Impact Marketing Ltd | Professional & scientific | 2020 |
| Software NOW Ltd | Wholesale & retail | 2025 |
| Sort & Save Limited | Water & waste | 2018 |
| South Wales Shoulder and Elbow Clinic Limited | Health & social care | 2014 |
| Spatter Ltd | Administrative & support | 2017 |
| Spice Inoculants Ltd | Professional & scientific | 2025 |
| Sport and Exercise Medicine Wales Limited | Health & social care | 2013 |
| Sporting Constructs Consulting Ltd | Professional & scientific | 2024 |
| ST Brides Ltd | Construction | 2007 |
| ST James Stables Equestrian Limited | Agriculture & fishing | 2010 |
| Standby Construction Limited | Construction | 2005 |
| Standpoint Installations Ltd | Professional & scientific | 2009 |
| Staziker Jones Design Consultants Limited | Professional & scientific | 2003 |
| Steeple Chase Racing Ltd | Arts & recreation | 2026 |
| Step Change Ventures Limited | Administrative & support | 2016 |
| Stoneacre Group Limited | Real estate | 2016 |
| Stoneacre Property Ltd | Real estate | 2019 |
| Storage Design Limited | Manufacturing | 1996 |
| Stormz Community for Musical Arts CIC | Arts & recreation | 2020 |
| Strand Above Hair Ltd | Other services | 2024 |
| Strategy Partners Wales Limited | Professional & scientific | 1988 |
| Stuart Laidlaw Building Limited | Construction | 2015 |
| Studio Schmoo Ltd | Wholesale & retail | 2024 |
| Succeed Limited | Professional & scientific | 2020 |
| SUE Mcdonagh Gallery Limited | Arts & recreation | 2004 |
| Summit Venture Consulting Limited | Professional & scientific | 2024 |
| Sun FM Limited | Information & communication | 1994 |
| Sunset Fashions Limited | Wholesale & retail | 2009 |
| Surehome (Property) Ltd | Real estate | 2024 |
| Suremark (Facilities) Ltd | Administrative & support | 2014 |
| Sustainable Wick Community Group | Administrative & support | 2014 |
| Swansea Bay Radio Limited | Information & communication | 2004 |
| Systemglaze Ltd | Extraterritorial | 2011 |
| T J Car Sales Limited | Wholesale & retail | 2017 |
| T J Morgan (Barry) Limited | Manufacturing | 1998 |
| T J Service Centre Limited | Wholesale & retail | 2025 |
| T Mullins Property Limited | Real estate | 2026 |
| T.W Haulage Ltd | Transport & logistics | 2013 |
| Tallia Limited | Wholesale & retail | 2017 |
| Tanc Estates Limited | Real estate | 2020 |
| TAO Analytical Ltd | Professional & scientific | 2023 |
| Taylor'D Landscaping and Tree Work Ltd | Administrative & support | 2024 |
| TDI Properties Limited | Households | 2020 |
| TEC Cardiff Ltd | Hospitality | 2025 |
| Tecnik International Limited | Real estate | 1997 |
| Tegfan Limited | Financial services | 2025 |
| Telluric Land Remediation Limited | Water & waste | 2003 |
| Tensift Limited | | 1979 |
| Tepoztlan Productions Ltd | Information & communication | 2022 |
| Teulu Allen Limited | Real estate | 2016 |
| Teulu Vets Limited | Real estate | 2022 |
| Tgrgm Ltd | Professional & scientific | 2026 |
| TH & D Limited | Hospitality | 2024 |
| Thames Radio Ltd | Information & communication | 2016 |
| THE Afon Group Ltd | Professional & scientific | 2016 |
| THE Brunch HUT Limited | Hospitality | 2025 |
| THE Doorfather Ltd | Manufacturing | 2026 |
| THE Doorland Warehouse Ltd | Manufacturing | 2021 |
| THE Endurance Physio Limited | Education | 2016 |
| THE Farmer's Arms (Aberthin) Ltd | Hospitality | 2008 |
| THE Firewood Company (UK) Limited | Agriculture & fishing | 2019 |
| THE Glamorgan Hunt Limited | Agriculture & fishing | 2004 |
| THE Golden Hind Management Company Limited | Households | 2005 |
| THE Goodness Guide Limited | Other services | 2022 |
| THE Manor House ST. Hilary Limited | Health & social care | 1999 |
| THE Ogmore Angling Association Limited | Agriculture & fishing | 2001 |
| THE Performance Company (Cardiff) Ltd | Construction | 2007 |
| THE Ragan Investment Company Limited | Financial services | 2019 |
| THE Smart Family Investment Company Ltd | Real estate | 2018 |
| THE Sycamore Tree Limited | Hospitality | 2018 |
| THE Vale of Glamorgan Agricultural Society | Administrative & support | 2003 |
| THE Village Shop, Wick Ltd | Wholesale & retail | 2024 |
| THE Wardrobe Coffee Shop Ltd | Hospitality | 2024 |
| THE Woodstock House Management Company Limited | Real estate | 1989 |
| Thecrowd&I Limited | Professional & scientific | 2011 |
| Thermify Holdings Limited | Information & communication | 2020 |
| Thimble Property Ltd | Real estate | 2022 |
| Thimble Retail Ltd | Wholesale & retail | 2026 |
| Thomas Fide Ltd | Wholesale & retail | 2012 |
| Thornton Travel Ltd | Administrative & support | 2022 |
| Thrive for Limited | Administrative & support | 2019 |
| Thryve Medical Ltd | Wholesale & retail | 2025 |
| Time Pccm Ltd | Real estate | 2020 |
| Tiny House Glamping Limited | Real estate | 2026 |
| TJM Laser Limited | Manufacturing | 2020 |
| TK Tree Services Ltd | Administrative & support | 2025 |
| TL Safety Services Ltd | Manufacturing | 2026 |