| Synectic Systems Group Limited | Administrative & support | 2006 |
| Synectic Systems Limited | Extraterritorial | 1987 |
| Synectics EFX Limited | Professional & scientific | 2018 |
| Synectics Group Limited | Extraterritorial | 2009 |
| Synectics High Security Limited | Extraterritorial | 1986 |
| Synectics Industrial Systems Limited | Extraterritorial | 2006 |
| Synectics Managed Services Limited | Extraterritorial | 2006 |
| Synectics Mobile Systems Limited | Extraterritorial | 2006 |
| Synectics NO. 2 Limited | Extraterritorial | 2009 |
| Synectics PLC | Professional & scientific | 1983 |
| Synectics Security Limited | Extraterritorial | 2006 |
| Synectics Security Networks Limited | Extraterritorial | 1995 |
| Synectics Surveillance Technology Limited | Extraterritorial | 2006 |
| Synectics Technology Centre Limited | Extraterritorial | 1987 |
| Synergem Recruitment Limited | Administrative & support | 2012 |
| Synergis Trading Limited | Manufacturing | 2007 |
| Synergise Creative Digital Media Assets and Technology Ltd | Information & communication | 2023 |
| Synergy Automotive Engineering Ltd | Wholesale & retail | 2026 |
| Synergy Diamond Products Ltd | Mining & quarrying | 2021 |
| Synergy Electrical Contracting Ltd | Construction | 2023 |
| Synergy Homes Limited | Professional & scientific | 2002 |
| Synergy Orthotic Clinical Services Ltd | Health & social care | 2010 |
| Synergy Plus Healthcare Ltd | Health & social care | 2017 |
| Synergy Premium Management Ltd | Construction | 2024 |
| Synergy Sports Massage Therapy Limited | Health & social care | 2025 |
| Synergy Wake Limited | Wholesale & retail | 2022 |
| Syngensys Limited | Professional & scientific | 2021 |
| Synomos Limited | Professional & scientific | 2025 |
| Syntax Heating Systems Ltd | Construction | 2026 |
| Synthesis Architects 2 Limited | Professional & scientific | 2013 |
| Synthesis Architects Limited | Professional & scientific | 2003 |
| Syntro Consultancy Ltd | Professional & scientific | 2025 |
| Synvico Ltd | Wholesale & retail | 2025 |
| SYP Holdings Limited | Professional & scientific | 2006 |
| Sypg Limited | Other services | 2015 |
| Syphonic Management Ltd | Other services | 2014 |
| Sypta Properties Limited | Real estate | 1985 |
| Syrano Clinical Consultancy Ltd | Professional & scientific | 2022 |
| SYS (Scaffolding Hire & Sales) Ltd | Construction | 2007 |
| SYS Courses Limited | Health & social care | 2012 |
| SYS Private Limited | Hospitality | 2024 |
| SYS Supplies Ltd | Wholesale & retail | 2018 |
| SYS Training and Events Ltd | Education | 2021 |
| Sysbrain Ltd | Information & communication | 2002 |
| Sysheff Ltd | Real estate | 2022 |
| Sysr Limited | Health & social care | 2021 |
| Syss Ltd | Construction | 2020 |
| Syss Monitoring Limited | Administrative & support | 2022 |
| System & Technical Solutions Limited | Manufacturing | 1998 |
| System UK Shopfitters Limited | Construction | 2015 |
| Systematic Servicing (Equipment) Limited | Manufacturing | 1974 |
| Systems (Telecoms) Ltd | Wholesale & retail | 2000 |
| Systems Restore Ltd | Wholesale & retail | 2017 |
| Systems-Direct Limited | Wholesale & retail | 2015 |
| Systemsavvy Ltd | Information & communication | 2025 |
| SYT Wholesale Ltd | Wholesale & retail | 2016 |
| Szafari Transport Ltd | Transport & logistics | 2025 |
| SZJ Associates Ltd | Information & communication | 2019 |
| SZR Accountants Ltd | Professional & scientific | 2023 |
| Szydlowska Buliding Ltd | Other services | 2025 |
| T & a Autos Ltd | Wholesale & retail | 2026 |
| T & B Cakecraft Ltd | Hospitality | 2011 |
| T & C Harris Holdings Limited | Financial services | 2021 |
| T & C Refurb Ltd | Construction | 2017 |
| T & E Facades Limited | Construction | 2018 |
| T & H Property Solutions Ltd | Real estate | 2024 |
| T & L Johnston Ltd | Real estate | 2022 |
| T & N Pubco LLP | | 2021 |
| T & O Holdings Limited | Health & social care | 2019 |
| T & S Associates Limited | Administrative & support | 2002 |
| T & T Thornhill Engineering Limited | Manufacturing | 2009 |
| T & W Civil Engineering Limited | Construction | 1994 |
| T & W Civil Engineering Trustee Limited | Extraterritorial | 2024 |
| T & W Group Limited | Administrative & support | 2015 |
| T & W Holdings Limited | Professional & scientific | 1995 |
| T & W Plant Hire Limited | Administrative & support | 1995 |
| T a H Plumbing Limited | Construction | 2022 |
| T a Paving Ltd | Construction | 2011 |
| T and Z Limited | Wholesale & retail | 2007 |
| T B Atkins and SON Ltd | Construction | 2024 |
| T Cutts and SON Limited | Construction | 2013 |
| T Cutts Electrical Ltd | Construction | 2014 |
| T D Williams Engineering Solutions Ltd | Professional & scientific | 2018 |
| T Grayson Building & Joinery Ltd | Construction | 2015 |
| T H Luxton Ltd | Real estate | 2026 |
| T Harrison Property Ltd | Real estate | 2025 |
| T Hartley Construction Limited | Construction | 2024 |
| T Hawkins Builders Limited | Construction | 2022 |
| T Helliwell Haulage Limited | Transport & logistics | 2016 |
| T J Mercer Ltd | Other services | 2024 |
| T Jennings (Electrical) Limited | Construction | 2003 |
| T L Killis & Sons Limited | Financial services | 2011 |
| T Liptrott Floorings Limited | Wholesale & retail | 2019 |
| T M Hairsine Limited | Arts & recreation | 2019 |
| T Macdowel Limited | Extraterritorial | 2009 |
| T Mart Ltd | Wholesale & retail | 2025 |
| T Platt Limited | Hospitality | 2011 |
| T R J Properties Limited | Real estate | 2019 |
| T R Wotton Limited | Professional & scientific | 2016 |
| T Reilly Geopolitical Ltd | Professional & scientific | 2024 |