| Simply British Limited | Wholesale & retail | 2018 |
| Simply Communities CIC | Health & social care | 2025 |
| Simply Direct Ltd | Wholesale & retail | 2011 |
| Simply Kata Ltd | Professional & scientific | 2019 |
| Simply Loyal Limited | Professional & scientific | 2022 |
| Simply Slips Ltd | Wholesale & retail | 2026 |
| Simplybeds Online Ltd | Wholesale & retail | 2023 |
| Simran Fruits & VEG Ltd | Wholesale & retail | 2015 |
| Simstone Ltd | Manufacturing | 2025 |
| Sina Advisory Ltd | Real estate | 2026 |
| Sinaassociates Limited | Health & social care | 2025 |
| Sinai Hotel LLP | | 2024 |
| Sinamed Limited | Financial services | 2025 |
| Singarajah London Ltd | Wholesale & retail | 2026 |
| Singarajah Ltd | Wholesale & retail | 2020 |
| Sinjini Ltd | Health & social care | 2012 |
| Sinobang Consulting Service Limited | Wholesale & retail | 2025 |
| Sinplay Limited | Information & communication | 2026 |
| Sinsmart Ltd | Wholesale & retail | 2024 |
| SIR Old John Fleet Services Limited | Administrative & support | 2024 |
| Sirgoun Limited | Real estate | 2018 |
| Siriso Ltd | Professional & scientific | 2019 |
| Sirius 28 Ltd | Administrative & support | 2024 |
| Sirius Star Care Ltd | Health & social care | 2018 |
| Sirius Vibes Ltd | Wholesale & retail | 2026 |
| Sirty Limited | Real estate | 2021 |
| Sisters Kollection Ltd | Wholesale & retail | 2025 |
| Sistr Ltd | Arts & recreation | 2019 |
| SIT Transport Limited | Transport & logistics | 2023 |
| SIT Trucking Ltd | Transport & logistics | 2018 |
| Sitara Care Group Ltd | Health & social care | 2026 |
| Site Training Ltd | Education | 2023 |
| Sitesure Compliance Limited | Professional & scientific | 2026 |
| Sivapakkiam Real Estates Ltd | Real estate | 2021 |
| Sivaproperty Limited | Real estate | 2024 |
| SIX Dimensions Ltd | Wholesale & retail | 2013 |
| Siya Exchange Limited | Transport & logistics | 2026 |
| Siya Limited | Wholesale & retail | 2013 |
| Siya Sweetmart Limited | Wholesale & retail | 2017 |
| SIZ Secure Limited | Wholesale & retail | 2025 |
| Sizi Ltd | Wholesale & retail | 2019 |
| Sizzlecooker Limited | Hospitality | 2025 |
| SJ Construction (Wembley) Ltd | Construction | 2021 |
| SJ London Estate Ltd | Real estate | 2020 |
| SJ1 Properties Ltd | Real estate | 2024 |
| SJP Global Limited | Real estate | 2012 |
| SK Medical Products Ltd | Wholesale & retail | 2026 |
| SK Removal Limited | Transport & logistics | 2022 |
| SK SIP and Go Limited | Wholesale & retail | 2025 |
| SK Vehicles Ltd | Wholesale & retail | 2021 |
| Skandarani Ltd | Other services | 2023 |
| Skar Venture Limited | Real estate | 2018 |
| Skc&Sons Ltd | Hospitality | 2025 |
| Skiip Ltd | Information & communication | 2026 |
| SKILL2DEVELOP Limited | Education | 2021 |
| Skin by DR Y Ltd | Other services | 2025 |
| Skinagistics Limited | Health & social care | 2023 |
| Skincentive Limited | Administrative & support | 2019 |
| SKK Holdings Ltd | Administrative & support | 2015 |
| SKM Clothings Limited | Wholesale & retail | 2026 |
| SKN Digital Commerce Ltd | Wholesale & retail | 2025 |
| Skolex Ltd | Construction | 2023 |
| SKS Design & Construction Ltd | Construction | 2016 |
| Sky 23 Ltd | Hospitality | 2016 |
| Sky Car Sales Ltd | Wholesale & retail | 2025 |
| Sky Construct Ltd | Construction | 2019 |
| Sky Lemon Ltd | Wholesale & retail | 2022 |
| Sky PCO Car Rental Ltd | Administrative & support | 2024 |
| Skye (Bushey) Limited | Real estate | 2026 |
| Skye Consultancy (UK) Ltd | Construction | 2022 |
| Skyers Virtual Services Ltd | Administrative & support | 2025 |
| Skyland Tech Ltd | Extraterritorial | 2021 |
| Skylights Restaurant Ltd | Hospitality | 2019 |
| Skyline Services Ltd | Wholesale & retail | 2024 |
| Skylines Apartments Ltd | Real estate | 2026 |
| Skyport Worldwide Ltd | Transport & logistics | 2021 |
| Slawomir Wholesale Ltd | Wholesale & retail | 2026 |
| Sleek and Klick Ltd | Wholesale & retail | 2021 |
| Sleep Consciousness | Professional & scientific | 2012 |
| Sleepover London Ltd | Real estate | 2024 |
| Slicehut Ltd | Hospitality | 2026 |
| Slidewizardai Limited | Information & communication | 2023 |
| Slikk Ltd | Wholesale & retail | 2020 |
| SLK Photography Ltd | Extraterritorial | 2011 |
| SLL Property Investments GB Ltd | Real estate | 2020 |
| Sloane Trading Ltd | Wholesale & retail | 2021 |
| SM Divitae Limited | Health & social care | 2023 |
| SM Loyalty Engineering Limited | Professional & scientific | 2023 |
| SM PG Services Ltd | Households | 2018 |
| Smart AV Company Limited | Information & communication | 2002 |
| Smart Gift Advertising Ltd | Manufacturing | 2026 |
| Smart Leap Recruiters Ltd | Administrative & support | 2021 |
| Smart Planning Designs Ltd | Professional & scientific | 2015 |
| Smart Quest 84 Ltd | Construction | 2020 |
| Smart Quest Limited | Real estate | 2017 |
| Smart Security Services Providers Ltd | Administrative & support | 2012 |
| Smart System Limited | Construction | 2005 |
| Smart Systems London Ltd | Construction | 2020 |
| Smart Transport Limited | Transport & logistics | 2011 |
| Smart VEN Solutions Ltd | Real estate | 2025 |