| Tycoch Enterprises Limited | Real estate | 2003 |
| Tycoch Maisonettes Management Company Limited | Households | 1984 |
| Tyfu Community Enterprises CIC | Hospitality | 2012 |
| Tykoon Limited | Administrative & support | 2007 |
| Tyler Jenkins Limited | Wholesale & retail | 2005 |
| Tymski Limited | Professional & scientific | 2025 |
| Tynet Ltd | Transport & logistics | 2009 |
| Tynywaun Kennels Limited | Other services | 2022 |
| Tyregen (DE Metals) Ltd | Manufacturing | 2019 |
| Tyregen Holdings Limited | Financial services | 2016 |
| Tyregen UK Limited | Manufacturing | 2016 |
| Tyreman SAM Ltd | Wholesale & retail | 2024 |
| Tyres & Autocare Bridgend Ltd | Wholesale & retail | 2018 |
| Tyres UN Limited | Extraterritorial | 2023 |
| Tyrnant Ltd | Professional & scientific | 2026 |
| Tyrone Medical Equipment Limited | Wholesale & retail | 2024 |
| TŶ AUR Properties Ltd | Real estate | 2025 |
| TŶ Brownie Limited | Wholesale & retail | 2025 |
| Tŷ'R Gorsedd Limited | Real estate | 2024 |
| T’Challa Limited | Information & communication | 2025 |
| U Hear Limited | Wholesale & retail | 2009 |
| U S Enterprises Ltd | Hospitality | 2018 |
| U-Earth Biotech Ltd | Wholesale & retail | 2018 |
| Uandu Store Ltd | Wholesale & retail | 2026 |
| Ubuntu Community Radio CIC | Information & communication | 2026 |
| Ubuntu Harvests Ltd | Wholesale & retail | 2025 |
| Ucare Motoring Ltd | Wholesale & retail | 2020 |
| Ucompare Insurance Services Ltd | Financial services | 2018 |
| Uday & Partap Enterprises Limited | Hospitality | 2018 |
| UDT Group Ltd | Manufacturing | 2015 |
| Ugieside Ltd | Professional & scientific | 2026 |
| UHP Systems Limited | Manufacturing | 2014 |
| UK BMV Property Investments LP | | 2011 |
| UK Car Sales Limited | Wholesale & retail | 2006 |
| UK DAB Networks (Operations) Ltd | Information & communication | 2020 |
| UK Flange Ltd | Extraterritorial | 2023 |
| UK Foods Limited | Wholesale & retail | 2023 |
| UK Kebab House (Trading AS AWA) Ltd | Hospitality | 2022 |
| UK Life Limited | Professional & scientific | 2014 |
| UK Mezzanine Direct Ltd | Construction | 2022 |
| UK National Property Management Limited | Real estate | 2025 |
| UK One Stop Ltd | Professional & scientific | 2022 |
| UK Packed Foods Limited | Hospitality | 2023 |
| UK Refrigeration Services Limited | Energy | 2002 |
| UK Sites Limited | Information & communication | 2002 |
| UK to Europe Transport Ltd | Transport & logistics | 2020 |
| UK United Holding Investment Ltd | Administrative & support | 2010 |
| UK Used Clothing Ltd | Water & waste | 2024 |
| Ukcs Ltd | Other services | 2011 |
| Ukloupes Limited | Manufacturing | 2013 |
| Ukosh Group Ltd | Professional & scientific | 2018 |
| UL 14 Limited | Administrative & support | 2014 |
| Ulanik Ltd | Wholesale & retail | 2025 |
| Ulex Energy Ltd | Construction | 2025 |
| Ulianich Digital Solutions Ltd | Information & communication | 2025 |
| Ultimate Cleaning & Maintenance Group Ltd | Administrative & support | 2024 |
| Ultimate Distribution Ltd | Wholesale & retail | 2023 |
| Ultimate Fitness Training Ltd | Arts & recreation | 2013 |
| Ultimate Landlord Limited | Real estate | 2019 |
| Ultimate Property Dashboard Ltd | Information & communication | 2021 |
| Ultra-High Pressure Systems Ltd | Manufacturing | 2024 |
| Ultraviolet Beams Limited | Construction | 2018 |
| ULU Security Ltd | Administrative & support | 2025 |
| Umano Ltd | Information & communication | 2024 |
| Umbra Holdings Limited | Real estate | 2020 |
| Umer Limited | Health & social care | 2023 |
| Umfolozi Ltd | Professional & scientific | 2023 |
| Umutnaz Ltd | Hospitality | 2026 |
| Unbxd Studios Ltd | Professional & scientific | 2018 |
| Undalogic Ltd | Manufacturing | 2024 |
| Underhill Developments Limited | Construction | 1984 |
| Underhill Management Company Ltd | Arts & recreation | 2021 |
| UNG Brothers Ltd | Wholesale & retail | 2019 |
| UNI Editing Ltd | Administrative & support | 2019 |
| Unified Flavours CIC | Hospitality | 2024 |
| Unify Talent Ltd | Administrative & support | 2020 |
| Unigaff Limited | Administrative & support | 2009 |
| Unigaff Maintenance Limited | Real estate | 2019 |
| Unilift South Wales Limited | Administrative & support | 2007 |
| Unique Accessories Private Ltd | Wholesale & retail | 2025 |
| Unique Hair Design (Swansea) Limited | Other services | 2007 |
| Unique Keyrings Limited | Wholesale & retail | 2021 |
| Unique Life Ceremonies Ltd | Other services | 2016 |
| Unique Properties (Portugal) Limited | Hospitality | 2008 |
| Unique Underdogs Ltd | Professional & scientific | 2018 |
| Uniquely Minded CYF | Health & social care | 2022 |
| Unit Superheater Engineering Limited | Manufacturing | 2017 |
| Unitbirwelco Ltd | Financial services | 2018 |
| United Business Group UK Ltd | Manufacturing | 2018 |
| United Cymru Coaches Ltd | Extraterritorial | 2015 |
| United Filmdom Ltd. | Information & communication | 2012 |
| United Therapists Ltd | Other services | 2005 |
| United Welsh Coaches Ltd | Transport & logistics | 2010 |
| Unity Auto Repair Ltd | Wholesale & retail | 2026 |
| Unity Power Ltd | Construction | 2023 |
| Universal Applications Ltd | Information & communication | 2021 |
| Universal Exports (Swansea) Ltd | Professional & scientific | 1999 |
| Universal Hardware Supplies Limited | Wholesale & retail | 1999 |
| Universe 26 Ltd | Information & communication | 2026 |
| University Dental Care Limited | Health & social care | 2015 |