| Symmetricise Limited | Health & social care | 2013 |
| Symphony of Secrets Limited | Professional & scientific | 2025 |
| Symphony of Stone Ltd | Manufacturing | 2023 |
| Symply Group Limited | Extraterritorial | 2025 |
| Synamedi Writing Ltd | Professional & scientific | 2012 |
| Syncline Limited | Wholesale & retail | 2025 |
| Synergic UK Limited | Information & communication | 2003 |
| Synergy Assets Ltd | Real estate | 2017 |
| Synergy Devices Limited | Professional & scientific | 1997 |
| Synergy Flavours Limited | Manufacturing | 1989 |
| Synexus Solutions Limited | Administrative & support | 2005 |
| Synvestment Ltd | Administrative & support | 2015 |
| Sypulse Limited | Information & communication | 2011 |
| Syracuse Waste Limited | Other services | 2021 |
| SYS19 Ltd | Information & communication | 2016 |
| Sysnous Consulting Ltd | Information & communication | 2021 |
| System Infotech Consulting Ltd | Wholesale & retail | 2023 |
| System Revival Limited | Information & communication | 2014 |
| Systems & Network Solutions Limited | Information & communication | 1997 |
| Systral Ltd | Professional & scientific | 2009 |
| SZ Halal Meat Store Limited | Wholesale & retail | 2025 |
| Szaraniec Ltd | Other services | 2021 |
| SZM Codes Ltd | Education | 2021 |
| T & M Heating and Plumbing Ltd | Construction | 2026 |
| T & M Wellbeing Ltd | Health & social care | 2020 |
| T Ashwood Limited | Professional & scientific | 2016 |
| T H Heating Services Ltd | Construction | 2013 |
| T L Consulting Limited | Professional & scientific | 2017 |
| T L Smith Limited | Real estate | 2024 |
| T M Wallace & Co Ltd | Professional & scientific | 2018 |
| T S Housing Ltd | Real estate | 2024 |
| T T Touring Ltd | Arts & recreation | 2011 |
| T V F (UK) Limited | Public administration | 1983 |
| T Woodard Limited | Administrative & support | 2016 |
| T&C Investments Ltd | Administrative & support | 2016 |
| T&S Pharma Ltd | Professional & scientific | 2017 |
| T&S Surveying Equipment Hire Ltd | Administrative & support | 2024 |
| T&S Surveying Ltd | Construction | 2017 |
| T&T Supplier Limited | Wholesale & retail | 2015 |
| T-Guard Security Ltd | Administrative & support | 2026 |
| T.H Homez Limited | Real estate | 2025 |
| T.Hudson Electrical Contractors Ltd | Energy | 2022 |
| T.J Estates Limited | Real estate | 2023 |
| T.R.A Engineering Ltd | Construction | 2017 |
| T30 Gymnastics Club LLP | | 2022 |
| T3N Ltd | Administrative & support | 2019 |
| TA Arch UK Ltd | Real estate | 2017 |
| TA7 Limited | Wholesale & retail | 2024 |
| Taajir Ltd. | Wholesale & retail | 2024 |
| TAC Construction Limited | Construction | 2014 |
| Tactical Paws Limited | Other services | 2023 |
| Tactical Paws Training Ltd | Other services | 2023 |
| Tafe Scaffolding Ltd | Construction | 2026 |
| TAG Engineering Consultant Limited | Information & communication | 2026 |
| Tagline Mentorship CIC | Health & social care | 2025 |
| TAK Air Limited | Transport & logistics | 2010 |
| Take One Business Communications Ltd | Information & communication | 1996 |
| Takeabitebucks Ltd | Hospitality | 2024 |
| Takt Direct UK Limited | Administrative & support | 2018 |
| Takumi LZ Ltd | Wholesale & retail | 2026 |
| Talashire Dog Training Ltd | Other services | 2025 |
| Talent Hatch Global Limited | Administrative & support | 2026 |
| Talk Through Therapies and Wellness CIC | Education | 2022 |
| Talklab Ltd | Education | 2008 |
| Tall GUY Management Limited | Arts & recreation | 2013 |
| Tall Poppy Associates Ltd | Professional & scientific | 2004 |
| Tamara Beauty Limited | Other services | 2015 |
| Tamilar Kudigal | Health & social care | 2019 |
| Tanasie SC Ltd | Construction | 2022 |
| Tandem Dating Ltd | Other services | 2024 |
| Tangle Labs Ltd | Wholesale & retail | 2022 |
| Tank Asset Management Ltd | Real estate | 2021 |
| Tank Communications Ltd | Arts & recreation | 2011 |
| Tank Consultancy Services Ltd | Real estate | 2015 |
| Tannin and Oak Limited | Wholesale & retail | 2016 |
| Tanvic Trading Limited | Wholesale & retail | 2014 |
| Tanya Aésthetics Ltd | Other services | 2024 |
| TAP Creative CIC | Information & communication | 2021 |
| TAP Recruitment Ltd | Administrative & support | 2019 |
| Tapital Ltd | Financial services | 2023 |
| Tappaxi Ltd | Transport & logistics | 2023 |
| Tara Holdings Limited | Other services | 2022 |
| Tara's Trading Ltd | Wholesale & retail | 2014 |
| Tarantinos (Lincs) Limited | Hospitality | 2020 |
| Tarbiyya Tours Ltd | Administrative & support | 2020 |
| Tarbox Training Ltd | Other services | 2025 |
| Tarca Limited | Information & communication | 2008 |
| Target (Wycombe) Car and Van Hire | | 1991 |
| Tarot Reading's & Crystal Healing's Ltd | Health & social care | 2025 |
| Tarrantula Ltd | Arts & recreation | 1998 |
| Tasc Productions Ltd | Administrative & support | 2011 |
| Tasif (UK) Limited | Wholesale & retail | 2012 |
| Task Property Ltd | Real estate | 2025 |
| Taskeen Therapy Limited | Health & social care | 2025 |
| Taste Lahore (Pinner) Ltd | Hospitality | 2024 |
| Taste of INDIA1 Ltd | Hospitality | 2025 |
| Taste on the Go Ltd | Wholesale & retail | 2025 |
| Tastic Retailing Ltd | Hospitality | 2025 |
| Taurus Building Services (UK) Limited | Construction | 2007 |
| Taurus Energies Ltd | Wholesale & retail | 2022 |