| SIA Trading Partners Ltd | Wholesale & retail | 2021 |
| Sia's Apps Ltd | Professional & scientific | 2024 |
| Sidhu Coffee Lounge Ltd | Hospitality | 2017 |
| Sidhu Holdings Ltd | Real estate | 2017 |
| Sidra Hills Ltd | Administrative & support | 2022 |
| Sierra Properties Limited | Real estate | 2021 |
| Sifat Convenience Stores Ltd | Wholesale & retail | 2026 |
| Sifnek Investment Ltd | Real estate | 2025 |
| Sigma Design & Build Ltd | Manufacturing | 2021 |
| Signature One Sports Consulting Ltd | Arts & recreation | 2021 |
| Signature Stays Ltd | Real estate | 2026 |
| Silgrill Ltd | Hospitality | 2025 |
| Silhouette Lipo Ltd | Health & social care | 2019 |
| Silicon Alley Maintenance Services Limited | Administrative & support | 2017 |
| Silicon Select Ltd | Administrative & support | 2026 |
| Silk Way Properties Ltd | Real estate | 2024 |
| Silver Bricks Grabs Limited | Water & waste | 2019 |
| Silver Cross Property Limited | Real estate | 2026 |
| Silver Homes Construction Limited | Construction | 2020 |
| Silver Interiors Ltd | Professional & scientific | 2019 |
| Silver Verse Ltd | Wholesale & retail | 2024 |
| Silverback Media Ltd | Information & communication | 2022 |
| Silverlining Data Services Ltd | Information & communication | 2020 |
| Silverlinx Property Limited | Real estate | 2025 |
| Silverstones Management Ltd | Professional & scientific | 2025 |
| Silverton Fitzgibbon Limited | Professional & scientific | 2014 |
| Simac School of Mind, Body & Spirit Ltd | Education | 2018 |
| Simba BRU Coffee (Uxbridge) Ltd | Hospitality | 2026 |
| Simbal Enterprises Limited | Real estate | 2018 |
| Simco Homes (Clovers Court) Limited | Real estate | 2018 |
| Simon 2017 Ltd | Transport & logistics | 2018 |
| Simon Marshall Ltd | Extraterritorial | 2015 |
| Simple Freight Forwarding (SFF) Ltd | Professional & scientific | 2020 |
| Simple Learning Nurseries Ltd | Education | 2022 |
| Simply Burgers Ltd | Hospitality | 2024 |
| Simply CAB Ltd | Administrative & support | 2025 |
| Simply Education Holdings Ltd | Professional & scientific | 2012 |
| Simply Falafel Ltd | Hospitality | 2019 |
| Simply Lebanese Ltd | Hospitality | 2024 |
| Simply Scrumptious 82 Ltd | Hospitality | 2025 |
| Simply Snacks Limited | Hospitality | 2026 |
| Simplyz Investments Ltd | Real estate | 2018 |
| Simz Enterprises Ltd | Wholesale & retail | 2026 |
| Sina Aesthetics Limited | Wholesale & retail | 2026 |
| Sinfonia Cruise Limited | Transport & logistics | 2025 |
| Singh Grocers Limited | Wholesale & retail | 2011 |
| Singh Leite Holiday Home Limited | Hospitality | 2026 |
| Sinhalite Holdings Limited | Wholesale & retail | 2024 |
| Sinwar Ltd | Transport & logistics | 2024 |
| Sipson Property Ltd | Real estate | 2025 |
| SIR Quick Midnight Ltd | Construction | 2021 |
| Siraaj Investments Ltd | Real estate | 2026 |
| Sirax Ltd | Education | 1990 |
| Siretta Consulting Ltd | Information & communication | 2013 |
| Siri Medical Services Ltd | Health & social care | 2013 |
| Sirisura Wellness Limited | Wholesale & retail | 2026 |
| Sirius Construction Ltd | Construction | 2024 |
| Sirius Maintenance Limited | Construction | 2016 |
| Sisl.Global Ltd | Information & communication | 2022 |
| Siva Fuels Ltd | Wholesale & retail | 2024 |
| Sivan Ventures Ltd | Information & communication | 2023 |
| SIX Inches Limited | Real estate | 2008 |
| SJ Business Solutions Ltd | Professional & scientific | 2026 |
| SJ Kitchen Ltd | Hospitality | 2026 |
| Sjbl Ltd | Construction | 2025 |
| SJC Estates Limited | Households | 2000 |
| SK (Chingford) Limited | Real estate | 2017 |
| SK Accountants & Tax Advisers Ltd | Professional & scientific | 2024 |
| SK Ascot & Oxford Limited | Real estate | 2022 |
| SK Asset Management London Ltd | Real estate | 2022 |
| SK Collectables Ltd | Wholesale & retail | 2020 |
| SK Design and Developments Ltd | Construction | 2024 |
| SK Electrical SK Ltd | Construction | 2022 |
| SK Holdings London Limited | Real estate | 2003 |
| SK Hospitality Consulting Ltd | Wholesale & retail | 2022 |
| SK in Community Ltd | Education | 2026 |
| SK Investment Partners Ltd | Real estate | 2024 |
| SK Realty Ltd | Real estate | 2019 |
| SK Sarees & Textiles Ltd | Wholesale & retail | 2023 |
| Skanda Kutty Ltd | Wholesale & retail | 2022 |
| SKB Consultancy Limited | Professional & scientific | 2018 |
| Skellig Consulting Ltd | Financial services | 2023 |
| Skibro Technologies Limited | Information & communication | 2016 |
| Skill Invest Ltd | Construction | 2019 |
| Skillnestuk Ltd | Education | 2025 |
| Skills Global Limited | Information & communication | 2021 |
| SKM Consulting Limited | Professional & scientific | 2022 |
| SKM Planning & Design Ltd | Professional & scientific | 2016 |
| SKM Residential Ltd | Real estate | 2018 |
| SKM Traders UK Ltd | Wholesale & retail | 2023 |
| Skmn Investment Ltd | Real estate | 2020 |
| Skope Workspace Limited | Real estate | 2004 |
| SKR IT Consultancy Ltd | Information & communication | 2018 |
| SKS Fast Food Limited | Hospitality | 2021 |
| SKS Homes (Longfleet) Ltd | Real estate | 2022 |
| SKS PVT Ltd | Real estate | 2024 |
| SKV Holdings Limited | Real estate | 2020 |
| Sky Engineering Services Ltd | Manufacturing | 2018 |
| Sky Enterprises Limited | Wholesale & retail | 2024 |
| Sky Food Limited | Hospitality | 2017 |