| Sigallo Investments Ltd | Real estate | 2018 |
| Sigma Energy Enterprise Ltd | Other services | 2022 |
| Signature Contracting Limited | Administrative & support | 2024 |
| Signseal Ltd | Manufacturing | 2023 |
| Signup Studios Ltd | Information & communication | 2023 |
| Sildon Limited | Information & communication | 2021 |
| Sildon Properties Limited | Real estate | 2024 |
| Silk Road Finance Holdings Number Five Limited | Professional & scientific | 2019 |
| Silk Road Finance Holdings Number SIX Limited | Professional & scientific | 2019 |
| Silk Road Finance Number Five PLC | Financial services | 2019 |
| Silk Road Finance Number SIX PLC | Financial services | 2019 |
| Silky Sun Properties Ltd | Real estate | 2025 |
| Silsila Group Ltd | Wholesale & retail | 2026 |
| Silva LDN Construction Ltd | Construction | 2019 |
| Silver Blocks Limited | Real estate | 2019 |
| Silver Cord Limited | Health & social care | 2017 |
| Silver Healthcare Solutions Limited | Health & social care | 2016 |
| Silvera Property Partners Limited | Real estate | 2026 |
| Silvercroft Property Development Limited | Real estate | 2003 |
| Silverline Coach Hire Ltd | Transport & logistics | 2020 |
| Silverway Electrical Limited | Construction | 2008 |
| SIM Circuit Limited | Information & communication | 2012 |
| Sim-Game Construction Ltd | Construction | 2019 |
| Simms Estates Limited | Real estate | 2022 |
| Simoleon Limited | Construction | 2018 |
| Simon Hollingworth & Associates Limited | Professional & scientific | 2000 |
| Simon RAM Consultancy Services Limited | Professional & scientific | 2015 |
| Simons and Delf Rental Account LLP | | 2025 |
| Simons Family Properties Limited | Real estate | 2025 |
| Simple Administrative Solutions Limited | Administrative & support | 2025 |
| Simplexmedia Ltd | Professional & scientific | 2020 |
| Simplicity Heat Limited | Construction | 2018 |
| Simply Conflict Limited | Administrative & support | 2006 |
| Simply Fencing and Landscapes Limited | Administrative & support | 2023 |
| Simply Fencing and Landscaping (Essex) Limited | Administrative & support | 2025 |
| Simply Roofing (Southeast) Limited | Construction | 2016 |
| SIMPLY473 Ltd | Manufacturing | 2025 |
| Sims Construction Services Ltd | Construction | 2025 |
| Sims Fabrications Ltd | Construction | 2015 |
| Sincere Healthcare & Staffing Solutions Ltd | Health & social care | 2018 |
| Sinema Palace Limited | Information & communication | 2022 |
| Singer's Hair Limited | Other services | 2018 |
| Sinha ENT Limited | Health & social care | 2019 |
| Siobhan Clare Occupational Therapy Ltd | Health & social care | 2020 |
| SIP & Hydrate Limited | Manufacturing | 2024 |
| SIR Robert Electrical Ltd | Construction | 2023 |
| Sircyon Ltd | Wholesale & retail | 2023 |
| Sister Style Ltd | Wholesale & retail | 2020 |
| Site Check UK Ltd | Households | 2025 |
| Site Pro Services Limited | Construction | 2022 |
| Sixteenleewalk Ltd | Real estate | 2025 |
| Sixtyfour Spaces Ltd | Real estate | 2024 |
| SJ & SM Properties Ltd | Real estate | 2020 |
| SJ Agencies Limited | Real estate | 2022 |
| SJ Business Consultant Limited | Construction | 2019 |
| SJ Monk Contractors Limited | Construction | 2012 |
| SJ Personal Training Limited | Other services | 2021 |
| SJB Contracts Limited | Construction | 2015 |
| SJC Office Supplies Ltd | Other services | 2019 |
| SJD Property Management Limited | Real estate | 2026 |
| SJH Project Consultants Limited | Construction | 2018 |
| SJP Commercials Limited | Wholesale & retail | 2023 |
| SJR Electrical (U.K) Limited | Construction | 2022 |
| SJT Canvey Limited | Construction | 2020 |
| SJT Developments Limited | Construction | 2012 |
| SJT Earls Colne Limited | Construction | 2020 |
| SJT Pluto 1 Limited | Construction | 2024 |
| SJT Pluto 2 Limited | Construction | 2024 |
| SJT Property Group LLP | | 2018 |
| Sjwv Investments Limited | Real estate | 2014 |
| SK Design & Build Ltd | Construction | 2022 |
| SK Dune Ltd | Public administration | 2023 |
| SK Game Ltd | Information & communication | 2023 |
| SK Installation Limited | Information & communication | 2012 |
| SK Properties (Essex) Ltd | Real estate | 2019 |
| SK Social Care Ltd | Health & social care | 2018 |
| SK Traffic Management Limited | Other services | 2017 |
| SK Welding and Fabrication Limited | Manufacturing | 2019 |
| Skas Radiology Limited | Health & social care | 2014 |
| Skce Care Limited | Health & social care | 2023 |
| Skcg Electrical Ltd | Construction | 2011 |
| Skehill Engineering Ltd | Professional & scientific | 2017 |
| Skilled Solutions Limited | Professional & scientific | 2017 |
| Skillful Ocean Limited | Construction | 2021 |
| Skills Store Limited | Professional & scientific | 2025 |
| Skipell Holdings Limited | Professional & scientific | 2025 |
| Skipell Property Ltd | Real estate | 2024 |
| SKP Scaffolding Limited | Construction | 2017 |
| Sktr Project Management Ltd | Professional & scientific | 2014 |
| Sky Pubs Ltd | Hospitality | 2018 |
| Skydale Interiors Limited | Construction | 2014 |
| Skyland Homes Ltd | Real estate | 2021 |
| Skyline Air Conditioning Services Limited | Construction | 2005 |
| Skyline Building Projects Ltd | Construction | 2018 |
| Skyline FX Limited | Financial services | 2019 |
| Skyline Group Services Limited | Construction | 2022 |
| Skyline Maintenance & Cleaning Ltd | Administrative & support | 2026 |
| Skyline Mechanical Services Limited | Construction | 2021 |
| Skynet Texas Co. Ltd | Manufacturing | 2019 |
| Skytight Roofworks Ltd | Construction | 2022 |