| Squeaky's Clean Ltd | Administrative & support | 2025 |
| Squire Hire Ltd | Wholesale & retail | 2025 |
| SR Secretarial Services Ltd | Administrative & support | 2013 |
| SRA Engineering Services Limited | Manufacturing | 2002 |
| ST Andrews Major Golf Course Limited | Arts & recreation | 1992 |
| ST James Gardens (Barry) Freehold Limited | Households | 2019 |
| ST Lythans Caravan Storage Ltd | Transport & logistics | 2021 |
| ST. Athan Park Management Company Limited | Administrative & support | 1981 |
| ST. Osyth Residents Co. Limited | Real estate | 1975 |
| Staff Only Limited | Information & communication | 2007 |
| Stand Tall Strength and Wellbeing Ltd | Health & social care | 2022 |
| Stangate House Limited | Real estate | 1999 |
| Stanley Village Stores Limited | Real estate | 2026 |
| Starling Aircraft Maintenance Limited | Manufacturing | 2023 |
| Starlux Entertainment Limited | Arts & recreation | 2024 |
| Stay at Moloko Ltd | Professional & scientific | 2025 |
| Stay Blended Ltd | Administrative & support | 2025 |
| Steady Aviation Engineering Ltd | Professional & scientific | 2010 |
| Steel FIX Scaffolding Ltd | Construction | 2022 |
| Step by Step Childcare Limited | Health & social care | 2019 |
| Stephenson Property Solutions Ltd | Hospitality | 2025 |
| Sterling Payroll and Bookkeeping Ltd | Professional & scientific | 2013 |
| Stiwdio C3 Architecture & Design Ltd | Professional & scientific | 2020 |
| Stiwdio Mizzi-Harris Ltd | Professional & scientific | 2022 |
| Stokes Case Management Ltd | Health & social care | 2014 |
| Stone Plumbing and Heating Limited | Manufacturing | 2001 |
| Stonewell Investments Limited | Real estate | 2005 |
| Strata Climbing Walls Ltd | Arts & recreation | 2020 |
| Strategy Sense Ltd | Professional & scientific | 2022 |
| Strawberry Knickers Ltd | Other services | 2025 |
| Strawberry Marketing UK Ltd. | Professional & scientific | 2008 |
| Studio 34 Limited | Manufacturing | 2004 |
| Studio One Hundred Ltd | Other services | 2024 |
| Stwff Trading Limited | Wholesale & retail | 2015 |
| SUB8 Ltd | Real estate | 2020 |
| Suki & Ruby Ltd | Wholesale & retail | 2023 |
| Suki & Ruby Propertyinvestments Ltd | Real estate | 2025 |
| Sully Properties Limited | Real estate | 2000 |
| Sully Reclamation & Storage Ltd | Administrative & support | 2016 |
| Summit Financial Advisers and Wealth Management Ltd | Financial services | 2024 |
| Sun Screen IT Foundation Limited | Health & social care | 2017 |
| Sunshine Heat (UK) Ltd | Financial services | 2022 |
| Superhero Studios Limited | Information & communication | 2014 |
| Superpower Superfood Ltd | Public administration | 2020 |
| Supported Breaks Ltd | Health & social care | 2011 |
| Surplus Storage (Bridgend) Limited | Administrative & support | 2022 |
| Swam Trading Ltd | Wholesale & retail | 2021 |
| Sweet PEA Home Help Ltd | Administrative & support | 2025 |
| Swirl Investment Ltd | Real estate | 2022 |
| Swmm Barry Ltd | Wholesale & retail | 2025 |
| Swoop TM Limited | Professional & scientific | 2025 |
| Synergy ICT Limited | Information & communication | 2017 |
| Synergy-J Limited | Construction | 2022 |
| T and W Consulting Limited | Professional & scientific | 2023 |
| T. V. Transport Limited | Transport & logistics | 2003 |
| Tabernacl CYF | Arts & recreation | 2021 |
| TAG Safe Inspections Limited | Professional & scientific | 2022 |
| TAI Newydd Limited | Real estate | 1985 |
| Tair Gafr Wines CYF | Agriculture & fishing | 2022 |
| Take Five Tea & Coffee Ltd | Hospitality | 2026 |
| Taliesin Training Limited | Education | 2015 |
| Talywain Golf Centre Limited | Arts & recreation | 2024 |
| TAM35 Group UK Limited | Hospitality | 2026 |
| Tamanifest Ltd | Hospitality | 2025 |
| Tame and Tone Ltd | Other services | 2025 |
| Tanglewood Management Ltd | Real estate | 2025 |
| Taste of Nepal Ltd | Hospitality | 2026 |
| Taste of Turner Ltd | Hospitality | 2020 |
| Tathan Hall Management Company Limited | Households | 2019 |
| Tathan Investment Limited | Real estate | 2021 |
| Tathan Property Limited | Real estate | 2026 |
| Tax Tamer Limited | Information & communication | 2026 |
| TAXI4RENT Ltd | Transport & logistics | 2022 |
| Taylors SW Ltd | Hospitality | 2024 |
| Taymat Limited | Professional & scientific | 2009 |
| TBC Cardiff Property Holdings Ltd | Real estate | 2015 |
| TD1A Ltd | Construction | 2024 |
| Teach Therapy Limited | Education | 2012 |
| Techtrad Limited | Information & communication | 2026 |
| Tegwillsisw Ltd | Health & social care | 2024 |
| Teqnivent Limited | Wholesale & retail | 1992 |
| Terracode Limited | Information & communication | 2020 |
| Tewdric Energy Installations Ltd | Energy | 2021 |
| Tewdric Energy Ltd | Energy | 2020 |
| That Vegan Bodybuilder Ltd | Other services | 2022 |
| THE Amelia Methodist Trust Company Limited | Education | 1990 |
| THE Apogee Project at Ltd | Other services | 2022 |
| THE Balloon Boutique Barry Ltd | Administrative & support | 2026 |
| THE Barbershop ST Athan Limited | Other services | 2025 |
| THE Boston Tool Company Ltd | Manufacturing | 1996 |
| THE Brefi Group Limited | Professional & scientific | 1982 |
| THE Brew FOB Ltd | Hospitality | 2025 |
| THE Buck Bar Ltd | Hospitality | 2020 |
| THE Business Centre (Cardiff) Ltd | Real estate | 2012 |
| THE Buy Back Shop Ltd | Wholesale & retail | 2018 |
| THE Chard Group Limited | Health & social care | 2016 |
| THE Codfather Fish Bar Ltd | Hospitality | 2025 |
| THE Coven of the Vale Ltd | Arts & recreation | 2023 |
| THE Cssp Limited | Hospitality | 2026 |
| THE Cult of NIC Picture House Ltd | Information & communication | 2024 |