| Taqa Bratani Limited | London | 2006 |
| Taqa Bratani LNS Limited | London | 2007 |
| Taranaki Thru Tubing Tools Ltd | Aberdeen | 2023 |
| Tarlair Management Ltd | Aberdeen | 2016 |
| Tarmac Aggregates Limited | Birmingham | 1935 |
| Tarmac Caledonian Limited | Dunbar | 1997 |
| Tarmac Trading Limited | Birmingham | 1948 |
| Tartan Tree Ltd | London | 2015 |
| Tartans Bear Limited | Cardiff | 2026 |
| Tarzan Access Solutions Ltd | Blackpool | 2024 |
| Task-Pro (Aberdeen) Limited | Inverurie | 2009 |
| Tate Exploration Consultants Ltd. | York | 1998 |
| Tauris Capital Partners Limited | Bromley | 2017 |
| Taurus Metals Limited | London | 2023 |
| Taylor Energy Services Limited | Salisbury | 2005 |
| Taylor Intervention Limited | Hatton | 2022 |
| Taylor Marine Consultants Ltd | Forfar | 2019 |
| Taylormechanics Ltd | Perth | 2024 |
| Taylors Transport Limited | Oxford | 1994 |
| Taypro Ltd | Dundee | 2020 |
| Tayside Drilling Services Ltd | Dundee | 2020 |
| Tayside Loler Inspection Ltd | Montrose | 2016 |
| Taytech Services Limited | Stornoway | 2012 |
| TAZ Rock Contracting Ltd | Aberdare | 2023 |
| TAZ Rock Ltd | Cardiff | 2016 |
| TAZ Rock Services Ltd | Aberdare | 2017 |
| TBW Consultancy Services Ltd | Aberdeen | 2023 |
| TCO In-Well Technologies UK Ltd | Aberdeen | 2009 |
| TD Access Engineering Ltd | Blackpool | 2022 |
| Teal Farm Services Ltd | Washington | 2025 |
| Team Daylight Limited | Aberdeen | 2018 |
| Team Energy Resources Limited | London | 1987 |
| TEC Resources Ltd | Reigate | 2017 |
| Teccra Ltd. | Glasgow | 2017 |
| Tech Otlet Company Limited | Essex | 2022 |
| Tech-Terra Ltd | Aberdeen | 2020 |
| Techability Ltd | London | 2006 |
| Techmin Limited | London | 2019 |
| Technical Integrity Solutions Ltd | London | 2022 |
| Technical OIL Services Limited | London | 2016 |
| Technical Solutions Scotland Ltd | Montrose | 2008 |
| Technip Services Limited | Newcastle Upon Tyne | 2015 |
| Technip Ships One Limited | Newcastle Upon Tyne | 1988 |
| Technip UK Limited | Newcastle Upon Tyne | 1924 |
| Technipfmc PLC | Newcastle Upon Tyne | 2015 |
| Technoflair Ltd | Bury St. Edmunds | 2020 |
| Techspection Limited | Doncaster | 2017 |
| Techtrain (OIL & GAS) Ltd | Altrincham | 2022 |
| Tecoma Strategies Limited | London | 2020 |
| Tectosat Ltd | Reigate | 2016 |
| Teda Consulting Limited | Essex | 2003 |
| Tedac Ltd | Cardiff | 2015 |
| Teecem Ltd | Harrogate | 2015 |
| Teekay Petrojarl Floating Production UK Ltd. | London | 1989 |
| Teesdale Architectural Stone Limited | Leeds | 2004 |
| Teesside GAS & Liquids Processing | London | 1992 |
| Teesside Gasport Limited | London | 2017 |
| Teign Valley Training Ltd | Newton Abbot | 2019 |
| TEK International Ltd | Macclesfield | 2019 |
| Tekbek OIL & GAS Limited | Ilford | 2019 |
| Telfer Technology Limited | | 1997 |
| Telford International Limited | London | 1997 |
| Telluris Consulting Ltd | Keighley | 2003 |
| Temako Investment International Limited | London | 2016 |
| Temarise Gold Refinery Ltd | London | 2024 |
| Temarise Ltd | London | 2020 |
| Temple House Partners Ltd | London | 2026 |
| Tenacity (RYE) Limited | East Sussex | 2003 |
| Tendaie Corporation Trading OIL Limited | London | 2021 |
| Tende Energy Angola Limited | London | 2022 |
| Tendley Quarries Limited | Birmingham | 1986 |
| Tendring Mineral Services Limited | Alresford | 2022 |
| TERATERA13 Limited | Bristol | 2024 |
| Tern Energy Limited | Lymington | 2023 |
| Terngate Limited | Solihull | 2008 |
| Terra Core Mining Ltd | Waterlooville | 2024 |
| Terra Energy and Natural Resources U.K. Ltd | London | 2025 |
| Terra Energy Limited | Brierley Hill | 2019 |
| Terra Explore Ltd | Crawley | 2017 |
| Terra NI Global Ltd | London | 2026 |
| Terra Petroleum Ltd | London | 2023 |
| Terra Surveys Limited | Dunfermline | 2017 |
| Terrain Energy Limited | London | 2009 |
| Terrasustain Limited | London | 2024 |
| Terravision Exploration Limited | West Molesey | 2015 |
| Terre Rare Ltd | London | 2016 |
| Tertiary (Middle East) Limited | Macclesfield | 2001 |
| Tertiary Gold Limited | Macclesfield | 1995 |
| Tertiary Minerals PLC | Macclesfield | 1999 |
| Tetra Energies Ltd | Leigh-On-Sea | 2022 |
| Tetra Energy Alpha Ltd | Leigh-On-Sea | 2022 |
| Tetra Energy Beta Ltd | Leigh-On-Sea | 2022 |
| Tetra Energy Gamma Ltd | Leigh-On-Sea | 2015 |
| Tetra Energy UK Onshore Ltd | Leigh-On-Sea | 2006 |
| Tetra Investments Company U.K. Limited | Aberdeen | 2011 |
| Tetra Tech RPS Energy Limited | Abingdon | 1979 |
| Texadon Energy Ltd | London | 2016 |
| Texas Gold Mining Corp Limited | Renfrew | 2014 |
| Tgpp 2 Limited | London | 2006 |
| TGS Geophysical Company (UK) Limited | Weybridge | 2006 |