| T & N Management Limited | Real estate | 2010 |
| T Track Ltd | Construction | 2025 |
| T. Sloan Ltd | Construction | 2016 |
| T.R.Owens(Aural Plastics)Limited | Health & social care | 1959 |
| T.S. Ridley Building Contractors LLP | | 2009 |
| Tabrk Ltd | Real estate | 2025 |
| Tactical Housing Ltd | Real estate | 2024 |
| Takeaway Lebanese Ltd | Hospitality | 2023 |
| Talbot Court Management Limited | Households | 1971 |
| Talent Incorporated Limited | Information & communication | 2016 |
| Talk Horse Limited | Professional & scientific | 2024 |
| Talksolution Ltd | Information & communication | 2011 |
| Tallaght Financial Ltd | Financial services | 2014 |
| Tally HO Farm Limited | Wholesale & retail | 2002 |
| TAM Properties Limited | Real estate | 2021 |
| Tamara Law Ltd | Other services | 2020 |
| Tamarside (CA) Limited | Professional & scientific | 2024 |
| Tamarside (QS) Limited | Professional & scientific | 2024 |
| Tamarside South Limited | Professional & scientific | 2015 |
| Tangible Building Solutions Limited | Construction | 2007 |
| Tangier Lane Holdings Limited | Real estate | 2026 |
| Tangier Lane Management Company (Eton) Limited | Households | 1980 |
| Tanktap Beer Services Limited | Manufacturing | 2025 |
| Tanna Medical Ltd | Health & social care | 2015 |
| Taphouse Properties Ltd | Real estate | 2025 |
| Taproot LG Holdings Limited | Wholesale & retail | 2024 |
| Taproot Partnership Limited | Wholesale & retail | 2013 |
| Tarbay Lane Residents Association Limited | Households | 2021 |
| Tarrants Tree Surgery Ltd | Agriculture & fishing | 2019 |
| Taste Fresh Ltd | Transport & logistics | 2021 |
| Tasting Tutor Ltd. | Information & communication | 2016 |
| Taxent Ltd | Professional & scientific | 2010 |
| Tayba Ltd | Health & social care | 2023 |
| Taylor Court (Eton Wick) Right to Manage Company Limited | Households | 2019 |
| TAZ Begum Ltd | Health & social care | 2020 |
| TBF 5 Limited | Hospitality | 2014 |
| Tbfc Brickwork Ltd | Construction | 2026 |
| TCG Guardian 1 Limited | Professional & scientific | 2005 |
| TCG Guardian 2 Limited | Professional & scientific | 2005 |
| Tcoombe Motion Design Limited | Information & communication | 2019 |
| Tdmm Family Ltd | Wholesale & retail | 2026 |
| Teacher Train Limited | Education | 2012 |
| Teacher-Link Ltd | Administrative & support | 2022 |
| Team Visual Solutions Ltd | Administrative & support | 2009 |
| Teamar Ltd | Households | 2018 |
| Tecgenie Ltd | Information & communication | 2009 |
| Tech Corporation (GB) Limited | Information & communication | 2014 |
| Techagility Ltd | Information & communication | 2013 |
| Techfix Berks Limited | Other services | 2019 |
| Techniques Group Holdings Limited | Professional & scientific | 2024 |
| Technoir Films Limited | Information & communication | 2025 |
| Techqua (UK) Limited | Information & communication | 2010 |
| Techscape Limited | Professional & scientific | 2026 |
| Techunite Ltd | Administrative & support | 2021 |
| TED and SON Ltd | Construction | 2016 |
| Teddy's Playhouse Ltd | Arts & recreation | 2017 |
| Teefy Pharma Ltd | Health & social care | 2017 |
| TEK Solutions Ltd | Administrative & support | 2004 |
| TEK2 Consulting Limited | Professional & scientific | 2017 |
| Telenet Global Logistics Limited | Transport & logistics | 2000 |
| Teller Investments Limited | Real estate | 2025 |
| Telos Partners Digital Limited | Information & communication | 2022 |
| Telos Partners Group Limited | Professional & scientific | 2000 |
| Telos Partners International Limited | Administrative & support | 2006 |
| Telos Partners LLP | | 2013 |
| Telstra Associates Ltd | Professional & scientific | 2004 |
| Telstra International Ltd | Administrative & support | 2007 |
| Tempo Communications Ltd | Professional & scientific | 2017 |
| Tempstay Guaranteed Rents Ltd | Real estate | 2023 |
| Tempstay Ltd | Hospitality | 2020 |
| TEN Grand Limited | Wholesale & retail | 2025 |
| TEN66 Management Limited | Administrative & support | 2016 |
| Tenalbany Limited | Households | 2016 |
| Tenjin Training Limited | Education | 2017 |
| Tentacoo Limited | Information & communication | 2021 |
| TEP Training Limited | Extraterritorial | 2019 |
| Terranova M.I.D. Limited | Real estate | 2025 |
| Terrassen Holdings Limited | Professional & scientific | 1978 |
| Terrestrial Developments Ltd | Real estate | 2014 |
| Test Concrete Limited | Construction | 2021 |
| Test Kitchen Food Limited | Hospitality | 2021 |
| Testslick Limited | Information & communication | 2023 |
| Testwood Consultancy Limited | Professional & scientific | 2011 |
| TFC (Investment Properties) LLP | | 2006 |
| TG Deep Clean Limited | Administrative & support | 2023 |
| Thaam Limited | Arts & recreation | 2024 |
| Thai & Vietnamese Street Food Ltd | Hospitality | 2019 |
| Thames Building Consultancy Ltd | Real estate | 2006 |
| Thames Car Radio Limited | Wholesale & retail | 2009 |
| Thames Charters Ltd | Transport & logistics | 2023 |
| Thames Health (Osteopathy) | Health & social care | 2008 |
| Thames Lighting Limited | Manufacturing | 2026 |
| Thames Valley Anaesthesia Ltd | Health & social care | 2015 |
| Thames Valley Automotive Ltd | Wholesale & retail | 2013 |
| Thames Valley Upper Limb Surgery Ltd | Administrative & support | 2019 |
| Thameside Property Company Limited | Real estate | 1974 |
| Thanvi Consultants Ltd | Health & social care | 2013 |
| THE 2 & 4 Maidenhead Road Windsor RTE Company Limited | Professional & scientific | 2003 |
| THE Abbeyfield (Maidenhead) Society Limited | Health & social care | 1972 |
| THE Acre Residents Association Limited | Households | 1987 |