| Swoon London Limited | Wholesale & retail | 2019 |
| Sword Property Development Ltd | Real estate | 2020 |
| Swp-Training Limited | Education | 2026 |
| SWR Civils & Plant Ltd | Construction | 2019 |
| SWT Burton Ltd | Wholesale & retail | 2019 |
| SWT Online Ltd | Wholesale & retail | 2021 |
| Swtv Limited | Information & communication | 2012 |
| SXA Garage Ltd | Transport & logistics | 2024 |
| Sxbi Media Ltd | Information & communication | 2026 |
| SY Electrical Contractors Ltd | Construction | 2021 |
| Syanca Limited | Real estate | 2026 |
| Sydnope Housing Limited | Real estate | 1946 |
| Syed 313 Properties Limited | Real estate | 2024 |
| Syed Legal Contractor Limited | Professional & scientific | 2019 |
| Syed Property Ltd | Construction | 2022 |
| Sygil Group Limited | Financial services | 2011 |
| Sygnature Discovery Limited | Professional & scientific | 2004 |
| Sygnature Discovery Trustee Company Limited | Professional & scientific | 2011 |
| Syiok Festivals Ltd | Hospitality | 2025 |
| SYL Consulting Limited | Professional & scientific | 2016 |
| Sylcon Software Solutions Ltd | Information & communication | 2015 |
| Sylvan Enterprises Group Limited | Other services | 2021 |
| Sylvena Naturel Ltd | Other services | 2018 |
| SYM Cleaning Services Ltd | Administrative & support | 2024 |
| Sym-Plex Ltd | Wholesale & retail | 2025 |
| Sym-Wall Building Technologies Limited | Manufacturing | 2012 |
| Sym-Wall Modular Build Ltd | Construction | 2018 |
| Sym-Wall Plant Engineering Ltd | Professional & scientific | 2018 |
| Symbion Holdings (UK) Limited | Administrative & support | 2000 |
| Symbiosis Associates Ltd | Professional & scientific | 2024 |
| Symbiosis Health Limited | Health & social care | 2019 |
| Symmetry Chiropractic Limited | Health & social care | 2021 |
| Symor Ltd | Wholesale & retail | 2015 |
| Symphony Coatings (East Midlands) Limited | Manufacturing | 1989 |
| Symtech Cctv Limited | Administrative & support | 2018 |
| Symzee Properties Ltd | Real estate | 2025 |
| Synaegis Health Ltd | Health & social care | 2020 |
| Synapse Ecosystems Limited | Administrative & support | 2020 |
| Synapse Edge Ltd | Information & communication | 2026 |
| Synapse Project Consulting Limited | Professional & scientific | 2007 |
| Synarc Ltd. | Professional & scientific | 2011 |
| Sync Sell Limited | Wholesale & retail | 2025 |
| Synchrolink Ltd | Information & communication | 1999 |
| Synchrome Ltd | Real estate | 2021 |
| Synchromesh Solutions Ltd | Professional & scientific | 2021 |
| Synchrony Psychology Ltd | Health & social care | 2015 |
| Syncopate Media Ltd | Information & communication | 2011 |
| Syncsynergy Estates Limited | Real estate | 2021 |
| Syncsynergy Healthcare Ltd | Health & social care | 2019 |
| Synergent Ltd | Professional & scientific | 2021 |
| Synergi Digital Limited | Information & communication | 2013 |
| Synergia CHN Limited | Real estate | 2024 |
| Synergia IT Ltd | Information & communication | 2021 |
| Synergic Care Limited | Health & social care | 2021 |
| Synergix Sameday Solutions Limited | Transport & logistics | 2023 |
| Synergos Business Solutions Limited | Professional & scientific | 2004 |
| Synergy Advisors Limited | Professional & scientific | 2016 |
| Synergy Beauty (Nottingham) Limited | Other services | 2024 |
| Synergy Dynamics IT Solutions Ltd | Information & communication | 2026 |
| Synergy Health Management Ltd | Professional & scientific | 2026 |
| Synergy Holdco Ltd | Professional & scientific | 2020 |
| Synergy Investment Services Limited | Construction | 2017 |
| Synergy MA Ltd | Education | 2023 |
| Synergy Network Limited | Other services | 2008 |
| Synergy NG9 Ltd | Administrative & support | 2018 |
| Synergy Offshore Limited | Information & communication | 2024 |
| Synergy Smart Homes Limited | Construction | 2012 |
| Synergy Wellness Limited | Other services | 2026 |
| Synergywash Launderette Ltd | Wholesale & retail | 2026 |
| Synk Solutions UK Ltd | Professional & scientific | 2026 |
| SYNOV8 Ltd | Information & communication | 2026 |
| Synshield Fabrications Limited | Manufacturing | 2004 |
| Syntex Technology Limited | Wholesale & retail | 2022 |
| Synthesis Care Services Ltd | Health & social care | 2025 |
| Synthly Rock Ltd | Information & communication | 2022 |
| Syntix Assets Ltd | Real estate | 2026 |
| Syntix Group Holding Ltd | Real estate | 2025 |
| Syntix Properties Ltd | Construction | 2022 |
| Synurgy Ltd | Professional & scientific | 2012 |
| Syon Electrical Services Ltd | Construction | 2023 |
| Syon Legal and Construction Ltd | Professional & scientific | 2020 |
| System 4 Services Limited | Construction | 2000 |
| System Corporation Public Limited Company | Professional & scientific | 1998 |
| System Test Services Ltd | Information & communication | 2016 |
| System Variable Limited | Information & communication | 2025 |
| Systematic Review Solutions Limited | Professional & scientific | 2013 |
| Systems Creaters Limited | Professional & scientific | 2013 |
| SYSTEMS4HAIRLOSS Ltd | Other services | 2021 |
| Systream Ltd | Information & communication | 2015 |
| Syvo Ltd | Information & communication | 2026 |
| SYZ Capital Ltd | Professional & scientific | 2023 |
| SZ Motor Group Ltd | Wholesale & retail | 2021 |
| SZ Properties Beeston Ltd | Real estate | 2023 |
| SZ Property Group SPV1 Holdings Limited | Real estate | 2024 |
| SZ Property Group SPV2 Limited | Real estate | 2025 |
| SZ Service Centre Ltd | Wholesale & retail | 2025 |
| SZ52 Ventures Limited | Real estate | 2025 |
| SZH Properties Ltd | Real estate | 2022 |
| Sznajder Transport Ltd | Transport & logistics | 2023 |
| T & C Smart Repairs Limited | Wholesale & retail | 2025 |