| Singham Shopfront Shutters Limited | Construction | 2020 |
| Singhsberry Chadwell Heath Ltd | Wholesale & retail | 2026 |
| Single Solutions (London) Limited | Construction | 2017 |
| Sinha Digital Limited | Information & communication | 2018 |
| SIR Louis Logistics Ltd | Transport & logistics | 2026 |
| SIR Winston Churchill Educational Trust for the Deaf Limited | Health & social care | 1981 |
| Siri Computer Solutions Ltd | Other services | 2018 |
| SIS Life Ltd | Education | 2018 |
| SIS Properties Limited | Real estate | 2017 |
| Sisu Clothing Ltd | Wholesale & retail | 2026 |
| Site 79 Limited | Construction | 2015 |
| Site Forge Digital Limited | Information & communication | 2026 |
| Site Safety Tool-Box Talks Ltd | Information & communication | 2025 |
| Site Secure Fixings Ltd | Wholesale & retail | 2026 |
| Sitela Fruits Ltd | Wholesale & retail | 2011 |
| Situ Yonghui Ltd | Wholesale & retail | 2022 |
| Sivaram Properties Ltd | Real estate | 2026 |
| SIX Way Trading Limited | Real estate | 2015 |
| SIX Way Watford Ltd | Construction | 2025 |
| Sixsigma Ltd | Construction | 2026 |
| Sixway Films Limited | Information & communication | 2013 |
| SJ and R Property Ltd | Real estate | 2021 |
| SJ Beauty Limited | Other services | 2017 |
| SJ Cole Holdings Limited | Financial services | 2021 |
| SJ Dental Services Ltd | Health & social care | 2025 |
| SJ Facades Ltd | Construction | 2026 |
| SJ Prestige Events Ltd | Administrative & support | 2024 |
| Sjab Consultants Ltd | Construction | 2021 |
| Sjaydeals Ltd | Wholesale & retail | 2025 |
| SJB Building & Development Contractors Ltd | Construction | 2010 |
| SJB Medicals Limited | Health & social care | 2022 |
| SJC Plumbing Ltd | Construction | 2015 |
| Sjhg Trading Limited | Wholesale & retail | 2017 |
| SJK Creations Limited | Construction | 2012 |
| SJK Property Creations Limited | Real estate | 2025 |
| SJO Minibuses Limited | Transport & logistics | 2022 |
| Sjph Limited | Information & communication | 2016 |
| SJR (South East) Limited | Construction | 2013 |
| SJS Accountancy & Financial Management Ltd | Professional & scientific | 2024 |
| SJW Consulting Services Ltd | Professional & scientific | 2024 |
| SK & RK Limited | Real estate | 2024 |
| SK Beauty Collection Ltd | Other services | 2024 |
| SK Collections Ltd | Wholesale & retail | 2026 |
| SK Consulting & Project Management Services Limited | Administrative & support | 2010 |
| SK Dental Care Ltd | Health & social care | 2023 |
| SK Flavours Limited | Hospitality | 2025 |
| SK Flooring Contracts Limited | Construction | 2018 |
| SK Groundworks Ltd | Construction | 2013 |
| SK Homes Limited | Construction | 2006 |
| SK Homes London Limited | Real estate | 2015 |
| SK Imperial Cleaning Services Ltd | Administrative & support | 2025 |
| SK Infosystems Ltd | Information & communication | 2010 |
| SK Outsource Limited | Administrative & support | 2025 |
| SK Protection Limited | Other services | 2024 |
| Skanda Groups Ltd | Wholesale & retail | 2024 |
| Skat Analytics Limited | Information & communication | 2022 |
| Skater Uktis Ltd | Other services | 2022 |
| SKC Technologies Ltd | Information & communication | 2025 |
| SKD Global Networking Limited | Information & communication | 2015 |
| Skepta (UK) Ltd | Administrative & support | 2012 |
| SKG Construction Ltd | Construction | 2018 |
| Skilful Services Ltd | Wholesale & retail | 2026 |
| Skiliyo Ltd | Arts & recreation | 2025 |
| Skill Hire UK Limited | Hospitality | 2021 |
| Skillbase Corp Ltd | Administrative & support | 2026 |
| Skilled Carpentry Limited | Construction | 2022 |
| Skillistic Limited | Information & communication | 2022 |
| Skills 4 Education Ltd | Education | 2020 |
| Skills Bridge to Opportunity CIC | Manufacturing | 2026 |
| Skills Hire Limited | Administrative & support | 2025 |
| Skills Train Direct Limited | Professional & scientific | 2012 |
| Skillvest Solutions Ltd | Administrative & support | 2007 |
| Skingsley Holdings Ltd | Real estate | 2020 |
| Skinmod Limited | Health & social care | 2016 |
| Skinology London Ltd | Other services | 2024 |
| SKK Builders Ltd | Construction | 2024 |
| Skmediamarketing Ltd | Professional & scientific | 2026 |
| SKN & GLO Ltd | Wholesale & retail | 2025 |
| Skons Global Services Limited | Information & communication | 2022 |
| Skra Ltd | Professional & scientific | 2026 |
| Skrn Limited | Real estate | 2024 |
| SKS Doubleglazing Ltd | Manufacturing | 2017 |
| Sksl Properties Ltd | Real estate | 2024 |
| Skubiszewski Building Contractors Ltd | Construction | 2010 |
| SKV Essex Ltd | Wholesale & retail | 2023 |
| Sky Dream Construction Ltd | Construction | 2025 |
| Sky Facades Group Ltd | Construction | 2024 |
| Sky Facades Installation Ltd | Construction | 2016 |
| Sky Glister Ltd | Real estate | 2022 |
| Sky Great Planet Limited | Wholesale & retail | 2024 |
| Sky Grom Limited | Construction | 2013 |
| Sky Highest Ltd | Health & social care | 2009 |
| Sky Learning Hub Ltd | Administrative & support | 2014 |
| Sky Secure Services UK Ltd | Administrative & support | 2026 |
| Skyair Aircraft Maintenance UK Ltd | Manufacturing | 2025 |
| Skybound Interiors Ltd | Construction | 2024 |
| Skybridge Tickets Ltd | Administrative & support | 2025 |
| Skyco Construction (UK) Ltd | Construction | 2010 |
| Skyedge Builders Ltd | Information & communication | 2024 |
| Skyhigh Resources Ltd | Information & communication | 2024 |