| Syndeo Capital Limited | Financial services | 2016 |
| Synergy 7 Limited | Financial services | 2010 |
| Synergy Marine Ltd | Extraterritorial | 2024 |
| Syon Health Ltd | Other services | 2017 |
| Systemic Accountants Limited | Professional & scientific | 2025 |
| Systems by Design Ltd | Information & communication | 2019 |
| Szplit Limited | Information & communication | 2008 |
| T & B LEE Ltd | Construction | 2011 |
| T & C Printers (Management) Limited | Professional & scientific | 2002 |
| T & T Family Investment Ltd | Real estate | 2017 |
| T Collier Holdings Ltd | Financial services | 2022 |
| T D R Autos Limited | Wholesale & retail | 2019 |
| T G Shine Limited | Professional & scientific | 2022 |
| T J Electrical Limited | Construction | 2006 |
| T J Nash Ltd | Real estate | 2020 |
| T Joseph Associates Limited | Professional & scientific | 2013 |
| T L Electronics 2 Limited | Manufacturing | 2019 |
| T L Llewellyn Ltd | Other services | 2019 |
| T M Akers Limited | Other services | 2005 |
| T Mechanical Limited | Construction | 2019 |
| T Quartic Ltd | Professional & scientific | 2023 |
| T&C Building Services Limited | Construction | 2026 |
| T&M 2020 Property Ltd | Real estate | 2024 |
| T&M Resources Ltd | Information & communication | 2023 |
| T&Ml Ltd | Wholesale & retail | 2026 |
| T-Amiable Limited | Real estate | 2024 |
| T-Delight Ltd | Health & social care | 2021 |
| T-K Plumbing&Electrical Ltd | Construction | 2015 |
| T-Rex Properties Limited | Real estate | 2023 |
| T.Care London Ltd | Wholesale & retail | 2020 |
| T.K Electrical Contractors Ltd | Construction | 2016 |
| T.M.S Learning and Skills Support Ltd. | Professional & scientific | 2014 |
| T.S.M. Limited | Households | 1982 |
| T.W. Lamb Groundworks Limited | Other services | 2003 |
| TA Global Holdings Group Ltd | Wholesale & retail | 2026 |
| Taad Limited | Other services | 2009 |
| TAC Enterprises Limited | Information & communication | 2026 |
| Tactical Reload Limited | Information & communication | 2020 |
| TAF Construction Limited | Construction | 2017 |
| Taffrock Care Limited | Health & social care | 2022 |
| Tafz Limited | Information & communication | 2018 |
| TAG Design & Build Limited | Construction | 2020 |
| TAG Tree Care Kent Ltd | Administrative & support | 2026 |
| TAI Support Limited | Administrative & support | 2023 |
| Tailor Arif Limited | Other services | 2013 |
| Tailoringbydavidson Ltd | Wholesale & retail | 2025 |
| Taipas Food (UK) Limited | Hospitality | 2016 |
| Tairon Limited | Professional & scientific | 2024 |
| TAK IT Limited | Information & communication | 2019 |
| Talas London Ltd | Extraterritorial | 2025 |
| Talent 4 Teaching Ltd | Administrative & support | 2025 |
| TALENT121 Ltd | Administrative & support | 2016 |
| Taliesin Limited | Professional & scientific | 1996 |
| Taliessin Limited | Professional & scientific | 2013 |
| Talk & Move Ltd | Education | 2024 |
| Tallaght Consulting Limited | Professional & scientific | 2021 |
| Tamar Thames Limited | Professional & scientific | 2014 |
| Tamasha Bromley Limited | Hospitality | 2026 |
| Tamizhan Software Consulting Limited | Professional & scientific | 2023 |
| Tanb Ltd | Construction | 2020 |
| Tanchi Construction Ltd | Construction | 2019 |
| Tani Plastering Limited | Construction | 2023 |
| Tanna Electrical Contractors Limited | Construction | 1998 |
| Taplinscott Ltd | Information & communication | 2012 |
| Task Securityservices UK Ltd | Administrative & support | 2018 |
| Taste Trends Limited | Hospitality | 1993 |
| Tasty Claypot Ltd | Hospitality | 2025 |
| TAT Trading Limited | Professional & scientific | 2018 |
| Tatlax Ltd | Wholesale & retail | 2025 |
| Tauris Capital Partners Limited | Mining & quarrying | 2017 |
| Taurus Developments (London) Limited | Construction | 2015 |
| Taurus Holdings Ltd | Financial services | 2020 |
| Taurus Records (UK) Limited | Information & communication | 2004 |
| Tavernelle House RTM Company Limited | Households | 2023 |
| Taverners Place Codicote Management Company Limited | Households | 2017 |
| Tax Web Limited | Professional & scientific | 1998 |
| Taxi Trade London Limited | Wholesale & retail | 2018 |
| Tayese Academy of Arts & Culture London CIC | Information & communication | 2023 |
| Taylor Bromley Estates Ltd | Real estate | 2026 |
| Taylor Collective Properties Ltd | Real estate | 2026 |
| Taylor Made Electrical Services Ltd | Construction | 2019 |
| Taylor Made Technical Services Ltd | Construction | 2025 |
| Taylor Plumbing & Heating Ltd | Construction | 2022 |
| Taylor Woodrow Construction Midlands Limited | Wholesale & retail | 1965 |
| Taylor Woodrow-Anglian Limited | Professional & scientific | 1962 |
| Tazoo Limited | Professional & scientific | 2012 |
| Tbbc Kent Limited | Construction | 2021 |
| TBC Two Brothers Construction Limited | Construction | 2020 |
| Tbgymfit Ltd | Arts & recreation | 2026 |
| Tbrown Healthcare Services Ltd | Health & social care | 2018 |
| TC Smiles Ltd | Health & social care | 2013 |
| TD Electrical and Building Ltd | Construction | 2021 |
| TD Media PVT Ltd | Wholesale & retail | 2026 |
| TDC Fulfilment Ltd | Wholesale & retail | 2025 |
| TE Clinic Ltd | Education | 2021 |
| TE Zotaj Ltd | Construction | 2024 |
| Tea and Tales Ltd | Administrative & support | 2024 |
| Tea One Sugar Ltd | Professional & scientific | 2016 |
| Team Kitz Ltd | Wholesale & retail | 2026 |
| Teampact International Limited | Information & communication | 2022 |