| Shinfield Take Away Limited | Extraterritorial | 2010 |
| Shinwari Kebab Ltd | Manufacturing | 2025 |
| Shipshape Limited | Manufacturing | 1981 |
| Shipsmart Logistics Ltd | Other services | 2025 |
| Shire Court Residents Limited | Households | 1982 |
| Shirley-Young Limited | Agriculture & fishing | 1962 |
| Shiva Water UK Ltd | Water & waste | 2017 |
| Shivani Bhagi Global Coaching & Training Ltd | Professional & scientific | 2021 |
| Shivara PVT Ltd | Information & communication | 2025 |
| Shoeberry Management Services Ltd | Professional & scientific | 1998 |
| Shogun Commercial Ltd | Real estate | 2022 |
| Shogun Property Ltd | Real estate | 2018 |
| Shoker Property Investment Ltd | Real estate | 2023 |
| Shooting Stars 999 Uniforms and Props Limited | Arts & recreation | 2011 |
| Shopfitting Division Limited | Construction | 2017 |
| Shophub Digital Ltd | Information & communication | 2022 |
| Shore to Shore Limited | Other services | 2019 |
| Shorgan Ltd | Other services | 2025 |
| Shouse Development Company London Limited | Real estate | 2025 |
| Showbiz Performing Arts Academy LLP | | 2025 |
| SHP Building Limited | Construction | 2004 |
| Shree Ganesh Consultancy Ltd | Professional & scientific | 2025 |
| Shree Radhey Trading Ltd | Financial services | 2026 |
| Shreevas Limited | Real estate | 2024 |
| Shreeve Care Services Ltd | Health & social care | 2022 |
| Shriben Ltd | Wholesale & retail | 2026 |
| Shrink 1ST Limited | Manufacturing | 1981 |
| Shrivenham Fencing Limited | Construction | 2012 |
| Shrivenham Management Company Limited | Households | 2026 |
| Shrivfest 2026 CIC | Administrative & support | 2026 |
| SHS- Santos Home Services Ltd | Water & waste | 2023 |
| Shubert Dias Photography Limited | Professional & scientific | 2026 |
| Shubhkrishna Services Limited | Health & social care | 2019 |
| Shuna Property Ltd | Real estate | 2015 |
| Shuna Property Management Ltd | Real estate | 2018 |
| Shutterright Ltd | Manufacturing | 2019 |
| Siam Properties Ltd | Real estate | 2024 |
| Siam Smile Asian Supermarket 89.LTD Limited | Wholesale & retail | 2021 |
| Siam WOK Swindon Limited | Hospitality | 2025 |
| Sibbers Limited | Real estate | 2023 |
| Sibley Wellbeing Group (SWG) Limited | Hospitality | 2015 |
| SIC - Startin Immigration Centre Ltd | Information & communication | 2025 |
| Sicher Systems Ltd | Information & communication | 2026 |
| Sidelight Ltd | Information & communication | 2024 |
| Sidhu Solutions Limited | Information & communication | 2014 |
| Sidof Limited | Health & social care | 2017 |
| Sidrywall Ltd | Construction | 2025 |
| Sied Investments Limited | Real estate | 2021 |
| Sievo Ltd | Information & communication | 2013 |
| Sigma Car Care Ltd | Administrative & support | 2024 |
| Sign of Excellence Limited | Professional & scientific | 2010 |
| Signal Boost Digital Ltd | Information & communication | 2026 |
| Signature Benches Limited | Manufacturing | 2013 |
| Signature Build & Management Ltd | Construction | 2025 |
| Signature Landscapers Ltd | Agriculture & fishing | 2026 |
| Signifer Group Ltd | Information & communication | 2026 |
| Silbury House Management Limited | Households | 2015 |
| Silk Paths Limited | Other services | 2026 |
| Silken Villa Limited | Wholesale & retail | 2024 |
| Silkwood Properties Limited | Real estate | 2018 |
| Siltrans Logistics Ltd | Transport & logistics | 2019 |
| Silver Home Comforts Limited | Real estate | 2019 |
| Silver Knight Consulting Limited | Professional & scientific | 2002 |
| Silver Screen Stores Ltd | Wholesale & retail | 2019 |
| Silver Spring Automobile Ltd | Wholesale & retail | 2026 |
| Silver Star Analytics Limited | Information & communication | 2012 |
| Silver Trading Group Limited | Financial services | 2023 |
| Silverback Services Ltd | Construction | 2018 |
| Silverback Sport Ltd | Wholesale & retail | 2009 |
| Silverbooks Limited | Professional & scientific | 2013 |
| Silverlea Properties Ltd | Real estate | 2018 |
| Silverlight Solutions Limited | Information & communication | 2014 |
| Silverspoon Gurkha Ltd | Hospitality | 2024 |
| Sim's Kitchen GOA Ltd | Hospitality | 2024 |
| Simegs Ltd | Construction | 2025 |
| Simila Co., Ltd | Wholesale & retail | 2021 |
| Simkofor Ltd | Health & social care | 2014 |
| Simmons & Sons Ltd | Construction | 2019 |
| Simo Barber Ltd | Other services | 2023 |
| Simon Bottomley Ltd | Information & communication | 2014 |
| Simon Chase Haulage Ltd | Transport & logistics | 2017 |
| Simon Merwood-Palmer Master Data Management Ltd | Professional & scientific | 2023 |
| Simon Says Design Limited | Arts & recreation | 2013 |
| Simple Cypher Ltd | Arts & recreation | 2021 |
| Simple Day Limited | Administrative & support | 2021 |
| Simple Enough Ltd | Wholesale & retail | 2026 |
| Simple Search PMI Limited | Financial services | 2025 |
| Simple Search Recruitment Ltd | Administrative & support | 2025 |
| Simple SID Ltd | Hospitality | 2026 |
| Simpletech Support Limited | Real estate | 2000 |
| Simpletolet & Co. Limited | Real estate | 2015 |
| Simplicite Limited | Professional & scientific | 2013 |
| Simpliciter Omnia Ltd | Administrative & support | 2015 |
| Simplified Analytical Solutions Ltd | Professional & scientific | 2022 |
| Simply Chauffeured Limited | Transport & logistics | 2024 |
| Simply HSH Limited | Real estate | 2024 |
| Simply Sense-Ational Ltd | Wholesale & retail | 2025 |
| Simply Staunch Ltd | Wholesale & retail | 2024 |
| Simply-Deedpolls UK Limited | Other services | 2018 |
| Simply.Co.Uk Limited | Wholesale & retail | 2008 |