| Simbuild Developments Ltd | Construction | 2018 |
| Simcast Ltd | Information & communication | 2026 |
| Simco Property Limited | Real estate | 2014 |
| Simfoma Ltd | Health & social care | 2023 |
| Simmons Architects Ltd | Professional & scientific | 2019 |
| Simnat Demolition + LLP | | 2025 |
| Simnat Demolition Limited | Construction | 2025 |
| Simon Collister & Associates Ltd | Professional & scientific | 2014 |
| Simon Heath Consulting Limited | Professional & scientific | 2023 |
| Simons Property Developments Ltd | Real estate | 2022 |
| Simpat Ltd | Administrative & support | 2014 |
| Simple 4 YOU Ltd | Other services | 2026 |
| Simple Driver Solutions Ltd | Administrative & support | 2024 |
| Simple Recruitment Solutions Group Ltd | Administrative & support | 2010 |
| Simple Recruitment Solutions Ltd | Administrative & support | 2007 |
| Simplicity HR Limited | Administrative & support | 2012 |
| Simply Aesthetics by Nicole Ltd | Other services | 2026 |
| Simply Antivirus Ltd | Wholesale & retail | 2018 |
| Simply Continuing Healthcare CIC | Health & social care | 2022 |
| Simply Fabric Ltd | Wholesale & retail | 2021 |
| Simply Filed Limited | Administrative & support | 2022 |
| Simply Hub Ltd | Wholesale & retail | 2021 |
| Simply Local Ltd | Wholesale & retail | 2025 |
| Simply Plumbing and Heating Ltd | Construction | 2024 |
| Simply Roofline Ltd | Construction | 2006 |
| Simply Swaffer Home Ltd | Wholesale & retail | 2025 |
| Simply Wood Limited | Manufacturing | 2017 |
| Sina Healthtech Ltd | Health & social care | 2023 |
| Sinclair E Ltd | Real estate | 2018 |
| Sindall & Partners Group Ltd | Construction | 2026 |
| Singh Sabha Gurdwara Limited | Other services | 2001 |
| Singleout Limited | Households | 1997 |
| Sino-Britain Trading Limited | Manufacturing | 2005 |
| Sintra Services Ltd | Construction | 2026 |
| Sinvogue Limited | Wholesale & retail | 2022 |
| Sion Investments and Services Ltd | Real estate | 2020 |
| Siozos Medical Limited | Health & social care | 2018 |
| SIP N DIP Tacos Limited | Hospitality | 2025 |
| Sipan House Food Ltd | Hospitality | 2025 |
| Siphaus Ltd | Manufacturing | 2024 |
| Siplex Limited | Information & communication | 2012 |
| Sirius Properties Limited | Real estate | 2020 |
| Siscare Limited | Real estate | 2006 |
| Sispharm Limited | Professional & scientific | 2018 |
| Sissons Barn Limited | Hospitality | 2023 |
| Sistaglam Ltd | Wholesale & retail | 2025 |
| Sisters Developers Ltd | Real estate | 2025 |
| SIT & Stay Yorkshire Limited | Administrative & support | 2020 |
| Site a M11 Business Link Management Company Limited | Households | 2011 |
| Site B M11 Business Link Management Company Limited | Households | 2015 |
| Site Logistic Solutions Ltd | Construction | 2024 |
| Site SPY Limited | Administrative & support | 2021 |
| Site Wide Recruitment Ltd | Administrative & support | 2022 |
| Sitesecuresecurity Limited | Administrative & support | 2023 |
| Sitevision Monitoring Limited | Administrative & support | 2025 |
| SIX Bricks Ltd | Construction | 2023 |
| SIX Pack Ltd | Hospitality | 2026 |
| SIXTEEN45 Limited | Hospitality | 2022 |
| Sixty Learn Ltd. | Information & communication | 2022 |
| SJ Beale HR Consult Ltd | Professional & scientific | 2007 |
| SJ Motor Vehicles Ltd | Wholesale & retail | 2025 |
| SJ Rendering Limited | Construction | 2014 |
| SJ TX Ltd | Wholesale & retail | 2022 |
| SJA Autos Ltd | Wholesale & retail | 2025 |
| SJA Locksmiths Limited | Administrative & support | 2026 |
| Sjdesigns Consulting Ltd | Professional & scientific | 2020 |
| SJF Management Consultancy Ltd | Administrative & support | 2012 |
| SJH Clinics Limited | Health & social care | 2025 |
| SJH Holdings Limited | Financial services | 2025 |
| SJK Nutrition Ltd | Other services | 2017 |
| SJL Property Refurbishments Limited | Administrative & support | 2023 |
| Sjlns Limited | Information & communication | 2015 |
| SJM Rural Ltd | Real estate | 2023 |
| SJR Executive Services Ltd | Transport & logistics | 2019 |
| SJS Carpet Cleaning Services Ltd | Administrative & support | 2026 |
| SJS Plastering Services Limited | Construction | 2003 |
| SJW Landscapes Limited | Administrative & support | 2024 |
| SJW Lettings Limited | Real estate | 2025 |
| SK BR Ltd | Transport & logistics | 2025 |
| SK Fleet Management Ltd | Transport & logistics | 2025 |
| SK Food Preparation Ltd | Hospitality | 2023 |
| SK Incorporations Limited | Transport & logistics | 2021 |
| SK Planings Limited | Construction | 2026 |
| Sk&Aa Properties Ltd | Real estate | 2025 |
| Sk&Kg Property Investments Limited | Real estate | 2026 |
| Sk&S Property Limited | Real estate | 2024 |
| Sk-Architecture Ltd | Professional & scientific | 2018 |
| SK6/FIVE Ltd | Wholesale & retail | 2019 |
| Skanda Padmanabhan Limited | Real estate | 2024 |
| Skapacorn Limited | Real estate | 2025 |
| SKB Enterprises UK Ltd | Manufacturing | 2021 |
| Skdj Ltd | Hospitality | 2018 |
| Skelton Dorans Technologies Limited | Professional & scientific | 2025 |
| Sketchycrow Designs Ltd | Information & communication | 2025 |
| Skeyton Residents Company Limited | Households | 2006 |
| Skillreactor Ltd | Education | 2021 |
| Skillz Sports Limited | Arts & recreation | 2022 |
| Skin & Beauty Rentals Limited | Other services | 2025 |
| Skin and Self Ltd. | Wholesale & retail | 2016 |
| Skin Sistas Clinic Ltd | Other services | 2025 |