| Trump Limited | Administrative & support | 2022 |
| Trussler-Jones Partnership Ltd | Administrative & support | 2003 |
| Trust Planet 3 Wealth Limited | Financial services | 2018 |
| Trusted Cleans & Laundry Ltd | Other services | 2025 |
| Trusted Mentor Ltd | Professional & scientific | 2017 |
| Truth Hurts Ltd | Professional & scientific | 2023 |
| TRV Multimedia Ltd | Information & communication | 2024 |
| Trwffl Limited | Manufacturing | 2017 |
| TRY Budget Genius Ltd | Financial services | 2025 |
| Trydan Engineering Ltd | Construction | 2024 |
| Tryhold Limited | Professional & scientific | 1997 |
| TSC General Services Limited | Transport & logistics | 2018 |
| Tscs OPS Limited | Construction | 2013 |
| Tsfk Ltd | Hospitality | 2025 |
| Tskd Retail Ltd | Wholesale & retail | 2023 |
| Tsp-Tech Limited | Manufacturing | 2023 |
| Tsrf Properties Ltd | Real estate | 2025 |
| Tstandop Ltd | Construction | 2026 |
| TT & KT Holdings Ltd | Financial services | 2020 |
| TT & KT Properties Ltd | Real estate | 2020 |
| TT Williams Holdings Limited | Professional & scientific | 2023 |
| TTJ Property Investment Ltd | Real estate | 2025 |
| Ttss Homes Limited | Construction | 2024 |
| Tuba Press Ltd | Information & communication | 2024 |
| Tube Access Scaffolding Ltd | Construction | 2023 |
| Tuckers (Swansea) Limited | Wholesale & retail | 1946 |
| Tuckers Butchers Limited | Wholesale & retail | 2003 |
| Tucket List Events Limited | Administrative & support | 2025 |
| Tudor Court 12-17 RTM Company Limited | Households | 2020 |
| Tudor Court 20-24 RTM Company Limited | Households | 2020 |
| Tudor Court 29-32 RTM Company Limited | Households | 2020 |
| Tudor Court 4-10 RTM Company Limited | Households | 2020 |
| Tudor Davies & Sons Limited | Construction | 2017 |
| Tudor House Apartments Management Limited | Real estate | 2014 |
| Tudorvend Limited | Wholesale & retail | 1988 |
| Tulip Engineering Consultancy Ltd | Professional & scientific | 2019 |
| Tumble New Build Ltd | Construction | 2026 |
| Tumble Tubs Limited | Other services | 2024 |
| Tuneup Digital Ltd | Professional & scientific | 2022 |
| Turkish Barber (Swansea) Limited | Other services | 2019 |
| Turkish Bazaar Ltd | Wholesale & retail | 2018 |
| Turmeric 14 Ltd | Hospitality | 2025 |
| Turn Key Property Developers Limited | Construction | 2025 |
| Turner Groundwork and Clearance Services Limited | Construction | 2014 |
| Turnercorp Ltd | Real estate | 2021 |
| Turnmil Engineering Limited | Professional & scientific | 2009 |
| Turnpike Foods Limited | Wholesale & retail | 1984 |
| Turrell Family Holdings Group Ltd | Professional & scientific | 2024 |
| Turrell Family Properties Ltd | Construction | 2019 |
| Turtle Tots South West Wales Ltd | Education | 2017 |
| Tuto Consulting Ltd | Information & communication | 2015 |
| TW Group (South Wales) Ltd | Construction | 2017 |
| Tw&I Ltd | Health & social care | 2021 |
| Twale Cuisine Limited | Manufacturing | 2015 |
| TWE Partnership Ltd | Real estate | 2019 |
| Tweed Medical Limited | Health & social care | 2017 |
| Twentieth Century Motors Limited | Wholesale & retail | 2016 |
| Twenty 23 Beauty Limited | Health & social care | 2016 |
| Twenty Three Leisure Ltd | Arts & recreation | 2024 |
| Twenty Two Drinks Ltd | Wholesale & retail | 2022 |
| TWG Town Planning Ltd | Professional & scientific | 2022 |
| Twice AS Nice (Mumbles) Limited | Wholesale & retail | 2003 |
| Twin Co Enterprises Limited | Financial services | 2020 |
| Twin Dragons Films Ltd | Information & communication | 2024 |
| Twin Oaks Properties Limited | Administrative & support | 2008 |
| Twist on the Go Ltd | Hospitality | 2026 |
| TWK Vehicle Sales Ltd | Wholesale & retail | 2024 |
| Two & ARO Ltd | Professional & scientific | 2018 |
| Two Magnolia Trees Limited | Hospitality | 2021 |
| Twogood Consultancy Ltd | Professional & scientific | 2013 |
| Twrch Services Limited | Professional & scientific | 2010 |
| TXC Developments Ltd | Real estate | 2026 |
| TY Alfie Property Holdings Ltd | Real estate | 2025 |
| TY Arian Limited | Professional & scientific | 2008 |
| TY Bach TWT Ltd | Real estate | 2023 |
| TY Coch Developments Ltd | Real estate | 2026 |
| TY Croeso (Ystradgynlais & District) Ltd. | Health & social care | 1996 |
| TY CWM Gwendraeth Limited | Health & social care | 2019 |
| TY Cwrw Ltd | Hospitality | 2019 |
| TY Davies and Sons Ltd | Hospitality | 2025 |
| TY Enfys Shamanic Activations Ltd | Health & social care | 2023 |
| TY Fforest Resource Hub CIC | Other services | 2021 |
| TY Gofalu Ltd | Health & social care | 2025 |
| TY Golwg Ltd | Real estate | 2025 |
| TY Gravenor Limited | Real estate | 2025 |
| TY Gwyn D.P Limited | Health & social care | 2007 |
| TY Gwyn Limited | Households | 1997 |
| TY Gwynne Property Ltd | Real estate | 2019 |
| TY Hapus Cymru Limited | Construction | 2015 |
| TY Hwyl Ltd | Health & social care | 2024 |
| TY Ilston Limited | Real estate | 2026 |
| TY Llewelyn Group Holdings Ltd | Health & social care | 2025 |
| TY Mawr Care Limited | Health & social care | 2020 |
| TY MOR Consultants Ltd | Professional & scientific | 2012 |
| TY Penfro Limited | Hospitality | 2020 |
| TY Sawna Ltd | Other services | 2022 |
| Ty'Risha Developments Limited | Construction | 2007 |
| Ty-Gwyn Techincal Services Limited | Professional & scientific | 2016 |
| Tyche Group Ltd | Real estate | 2022 |
| Tycoch Clothes Clinic Limited | Other services | 2022 |