| Sustainable Growth Management UK Limited | Professional & scientific | 2025 |
| Sustainable Landscapes Ltd | Administrative & support | 2017 |
| Sustainable South West Herts CIC | Professional & scientific | 2025 |
| Sutherland Avenue Residents Association Limited | Real estate | 1991 |
| Sutherland Court Management Company Limited | Households | 1987 |
| Sutton & Merton Out-Of-Hours Co-Operative | Health & social care | 2004 |
| Suusco Ltd | Wholesale & retail | 2021 |
| Suzzy Healthcare Limited | Health & social care | 2019 |
| SV OM Limited | Real estate | 2021 |
| Svar Consultants Limited | Extraterritorial | 2012 |
| Svart Home Ltd | Construction | 2020 |
| SVB Retail Ltd | Wholesale & retail | 2025 |
| SVK Group Ltd | Other services | 2019 |
| SVR Lifestyle Ltd | Professional & scientific | 2021 |
| SW Site Management Services Ltd | Construction | 2025 |
| SW5 Hair Limited | Other services | 2019 |
| Swaine Property Consultancy Limited | Professional & scientific | 2007 |
| Swallows Field (Hemel Hempstead Management Company Ltd | Households | 2015 |
| Swami Limited | Real estate | 2023 |
| Swan Windows Ltd | Extraterritorial | 2025 |
| Swancrest Properties Limited | Construction | 2024 |
| Swanford Lettings Ltd | Real estate | 2016 |
| Swanley Court Management Company Limited | Real estate | 1991 |
| Swansbrook Business Solutions Limited | Administrative & support | 2019 |
| Swanscombe Development LLP | | 2015 |
| Swarag Consulting Limited | Information & communication | 2011 |
| Swastik Consulting Ltd | Information & communication | 2024 |
| Swati Consultancy Ltd | Professional & scientific | 2015 |
| SWB Luxury Limited | Wholesale & retail | 2020 |
| Sweech Data Solutions Ltd | Information & communication | 2017 |
| Sweech Properties Ltd | Real estate | 2022 |
| Sweet Blessings Ltd | Hospitality | 2017 |
| Sweet Buds Limited | Hospitality | 2024 |
| Sweet Home Property Limited | Real estate | 2016 |
| Sweet Things (UK) Limited | Wholesale & retail | 2002 |
| Sweetcroft Bespoke Joinery Ltd | Manufacturing | 2025 |
| Sweetcroft Properties Limited | Real estate | 2019 |
| Sweetness Health Ltd | Manufacturing | 2021 |
| Swetsha Ltd | Real estate | 2017 |
| Swfs Holdings Limited | Financial services | 2023 |
| Swfs Properties Limited | Real estate | 2016 |
| Swift Cooling and Heating Solutions Limited | Construction | 2018 |
| Swift Pro Support Services Limited | Administrative & support | 2024 |
| Swift Purchase Limited | Wholesale & retail | 2021 |
| Swiftfix Luton Limited | Real estate | 2026 |
| Swiftpro Corporation UK Ltd | Information & communication | 2013 |
| Swifttrail Ltd | Transport & logistics | 2025 |
| Swindon Hydraulics Ltd | Administrative & support | 2019 |
| Swirlbuild Limited | Real estate | 1995 |
| Swiss Property Partners Ltd | Real estate | 2016 |
| Switch Technologies Limited | Construction | 2016 |
| Sword Holdings Ltd | Financial services | 2012 |
| Syco Developments Ltd | Real estate | 2018 |
| SYD Consulting Ltd | Professional & scientific | 2025 |
| Sydell Holding Company UK Ltd | Financial services | 2024 |
| Sydell London Ltd. | Professional & scientific | 2013 |
| Sydney Place Ltd | Real estate | 2022 |
| SYL Homes Ltd | Real estate | 2025 |
| SYL Legacy Partners Ltd | Arts & recreation | 2025 |
| SYL Property Management Ltd | Real estate | 2020 |
| SYL Serviced Accommodation Ltd | Real estate | 2019 |
| SYL Sports & Wellness Ltd. | Arts & recreation | 2015 |
| Sylhet 97 Ltd | Hospitality | 2019 |
| Sylvan Court Limited | Real estate | 2017 |
| Sylvan Moon Limited | Professional & scientific | 1996 |
| Sylvester's Recruitment Ltd | Administrative & support | 2025 |
| Syme & Duncan,Limited | Professional & scientific | 1915 |
| Symply Holdings Limited | Professional & scientific | 2011 |
| Symply Pet Foods Limited | Administrative & support | 2009 |
| Synagora Ltd | Wholesale & retail | 2026 |
| Synchromatica Ltd | Information & communication | 2010 |
| Syndesis Group Ltd | Wholesale & retail | 2022 |
| Syndicate Limited | Real estate | 1992 |
| Syndicate Technical Solutions Ltd | Construction | 2014 |
| Synergi Search & Select Limited | Administrative & support | 2002 |
| Synergy Eco Ltd | Construction | 2021 |
| Synergy Hotels (Aberdeen) Limited | Hospitality | 2018 |
| Synergy Hotels LLP | | 2011 |
| Synergy International Partners Ltd | Administrative & support | 2017 |
| Synergy Reporting Ltd | Health & social care | 2021 |
| Synesit Limited | Information & communication | 2011 |
| Synex Trading Ltd | Wholesale & retail | 2023 |
| Synoptic (Consulting Engineers) Limited | Professional & scientific | 2012 |
| Synoptica Limited | Administrative & support | 2000 |
| Synovia Limited | Wholesale & retail | 2025 |
| Synrg Plumbing and Heating Ltd | Construction | 2025 |
| Synthax Audio (UK) Limited | Wholesale & retail | 2002 |
| SYP Optics Limited | Information & communication | 2024 |
| System Bookkeepers Ltd | Professional & scientific | 2023 |
| Systemic Solutions Ltd | Information & communication | 2025 |
| Systemshum Ltd | Information & communication | 2012 |
| T & a Architectural Ironmongery Limited | Other services | 1994 |
| T & C Surfacing and Groundworks Holdings Limited | Financial services | 2019 |
| T & C Surfacing and Groundworks Limited | Construction | 2010 |
| T & I Immigration Advisers Ltd | Professional & scientific | 2026 |
| T & L Retail Ltd | Wholesale & retail | 2019 |
| T & L Services Ltd | Wholesale & retail | 2017 |
| T & Leigh Ltd | Professional & scientific | 2020 |
| T & SC Solutions Limited | Professional & scientific | 2007 |
| T a Morgan Ltd | Construction | 2023 |