| Silversight Systems Limited | Manufacturing | 2006 |
| Silverstar Automotive Ltd | Wholesale & retail | 2024 |
| Silverthorn Engineers Limited | Manufacturing | 2003 |
| Silverwise Group Limited | Administrative & support | 2022 |
| Silviu Ltd | Transport & logistics | 2013 |
| SIM S.E Ltd | Construction | 2012 |
| Sim's Golf Limited | Arts & recreation | 2025 |
| Sim-Inves Limited | Real estate | 2016 |
| Sima Management Consultancy Limited | Professional & scientific | 2014 |
| Simah Ltd | Hospitality | 2025 |
| Simarson Building Contractors Limited | Construction | 2021 |
| Simba Domains Ltd | Information & communication | 2016 |
| Simba Meat Ltd | Wholesale & retail | 2025 |
| Simba Property Ventures Ltd | Real estate | 2026 |
| Simbal Systems Ltd | Information & communication | 2020 |
| Simbano and Sons Ltd | Transport & logistics | 2022 |
| Simbha Property Consultancy Limited | Professional & scientific | 2021 |
| Simblo Ltd | Professional & scientific | 2026 |
| Simchoice Ltd | Administrative & support | 2016 |
| Simco Design and Build Ltd | Construction | 2015 |
| Simhill Builders Limited | Construction | 2014 |
| Simi Collections Ltd | Wholesale & retail | 2019 |
| Simi Fashion Ltd | Wholesale & retail | 2010 |
| Simi Global Ltd | Wholesale & retail | 2024 |
| Simi Trans Ltd | Transport & logistics | 2018 |
| Simi's Unique Treasures Ltd | Wholesale & retail | 2024 |
| Simkay IT Consulting Ltd | Information & communication | 2020 |
| Simkin Property Ltd | Real estate | 2025 |
| Simmonds Clinical Solutions Limited | Health & social care | 2024 |
| Simmonds Ford Trustees Limited | Extraterritorial | 2001 |
| Simo Université Ltd | Information & communication | 2025 |
| Simon Dean Design Limited | Construction | 2024 |
| Simon Elday Limited | Construction | 2026 |
| Simon Erica Properties Ltd | Real estate | 2023 |
| Simon Gilbert Consultancy Limited | Professional & scientific | 2014 |
| Simon Golding Ltd | Manufacturing | 2002 |
| Simon Grace Automotive Ltd | Wholesale & retail | 2019 |
| Simon Harrison Computer Services Ltd | Information & communication | 2018 |
| Simon Houseman Limited | Financial services | 2009 |
| Simon Rogers Electrical Limited | Construction | 2009 |
| Simon Wood Golf Ltd | Administrative & support | 2013 |
| Simon's Machine Tool Services Limited | Administrative & support | 2006 |
| Simone Life Ltd | Health & social care | 2023 |
| Simons Group Limited | Construction | 1987 |
| Simopharma UK Ltd | Administrative & support | 2024 |
| Simpack Properties Limited | Real estate | 2020 |
| Simple Fire Assessments Ltd | Professional & scientific | 2025 |
| Simple Home Move Limited | Financial services | 2014 |
| Simple Merchant Services Limited | Administrative & support | 2018 |
| Simple Sellers Ltd | Real estate | 2018 |
| Simple Solar Ltd | Construction | 2025 |
| SIMPLE2MOOVE Ltd | Transport & logistics | 2023 |
| Simplefficient Bookkeeping Limited | Professional & scientific | 2017 |
| Simplex (UK) Ltd | Wholesale & retail | 2013 |
| Simplicity Specialist Finishes Ltd | Construction | 2016 |
| Simplified Bookkeeping Ltd | Professional & scientific | 2021 |
| Simplify Recruitment Limited | Administrative & support | 2019 |
| Simplit Solutions Ltd | Information & communication | 2012 |
| Simply A-Z Solutions Limited | Hospitality | 1995 |
| Simply Autos Ltd | Wholesale & retail | 2024 |
| Simply Basic Ltd | Manufacturing | 2019 |
| Simply Fitted Kitchens Ltd | Manufacturing | 2025 |
| Simply Gorgeous Limited | Real estate | 2010 |
| Simply Guided CIC | Health & social care | 2024 |
| Simply Halal Ltd | Manufacturing | 2020 |
| Simply Indian Leicester Ltd | Hospitality | 2021 |
| Simply Indian Takeaway Limited | Hospitality | 2023 |
| Simply Intelligent Properties Ltd | Real estate | 2018 |
| Simply Kitchens Blaby Ltd | Manufacturing | 2023 |
| Simply Living (Leicester) Limited | Real estate | 2017 |
| Simply Marah Optics Ltd | Health & social care | 2022 |
| Simply Menopausal Ltd | Administrative & support | 2017 |
| Simply NSN Limited | Professional & scientific | 2016 |
| Simply Online Limited | Wholesale & retail | 2015 |
| Simply Organised Limited | Administrative & support | 2019 |
| Simply Park & FLY Ltd | Transport & logistics | 2012 |
| Simply Trade Plate Recruitment Ltd | Professional & scientific | 2025 |
| Simply Triptyk Holdings Limited | Financial services | 2018 |
| Simply Tyres Midlands Limited | Wholesale & retail | 2026 |
| Simply Wash & DRY Leicester Ltd | Administrative & support | 2026 |
| Simply Wash & DRY Limited | Administrative & support | 2017 |
| Simposh Ltd | Construction | 2006 |
| Simpra Financial Services Ltd | Professional & scientific | 2023 |
| Simpson & Ruxton Limited | Wholesale & retail | 2003 |
| Simpson House Management Company Limited | Households | 2006 |
| Simraj Kaur Ltd | Wholesale & retail | 2017 |
| Simran Design Ltd | Professional & scientific | 2021 |
| Simran Hope Ltd | Hospitality | 2017 |
| Simran Kataorha Ltd | Health & social care | 2026 |
| Simran Ltd | Manufacturing | 2018 |
| Simss Services Ltd | Transport & logistics | 2025 |
| Simtec Materials Testing Ltd | Professional & scientific | 2007 |
| Simtech Consulting Ltd | Administrative & support | 2018 |
| Simtrain Ltd | Administrative & support | 2024 |
| SIN Motors Ltd | Wholesale & retail | 2024 |
| Sina Hair & Beauty Ltd | Other services | 2022 |
| Sinajay Leisure Limited | Arts & recreation | 2010 |
| Sinal Investments 2 Ltd | Administrative & support | 2024 |
| Sinal Investments Ltd | Households | 2021 |
| Sinava 1 Limited | Wholesale & retail | 2019 |