| Silvio Dante Ltd | Financial services | 2024 |
| SIM IT Ltd | Information & communication | 2014 |
| Simeonov Investment Ltd | Real estate | 2026 |
| Simerjeet Singh Ltd | Construction | 2017 |
| Simfield Access Solutions Ltd. | Construction | 2010 |
| Simlight Luxe Ltd | Wholesale & retail | 2025 |
| Simmer and Slice Ltd | Wholesale & retail | 2023 |
| Simon Bowler Enterprises Limited | Professional & scientific | 2021 |
| Simon Bunn International UK Ltd | Wholesale & retail | 2025 |
| Simon David Ltd | Other services | 2024 |
| Simon Dean Motor Services Ltd | Wholesale & retail | 2002 |
| Simon Pyatt Electrical Services Ltd | Construction | 2008 |
| Simonburn Estates Limited | Real estate | 2011 |
| Simons and SON Limited | Transport & logistics | 2010 |
| Simple Accountancy Services Ltd | Professional & scientific | 2017 |
| Simple Accounts 123 Limited | Professional & scientific | 2020 |
| Simple Football Ltd | Wholesale & retail | 2025 |
| Simplerstays Management Ltd | Real estate | 2023 |
| Simpli.Life CIC | Other services | 2023 |
| Simplicity 1976 Ltd | Professional & scientific | 2023 |
| Simply Amazing Beauty Ltd | Other services | 2024 |
| Simply Desserts Ltd | Hospitality | 2025 |
| Simply Healthy Transport Ltd | Transport & logistics | 2020 |
| Simply Hygiene Washroom Solutions Limited | Water & waste | 2009 |
| Simply Solar (Staffs) Limited | Construction | 2026 |
| Simply Somerset Ltd | Wholesale & retail | 2019 |
| Simply Stadia Seating Ltd | Construction | 2022 |
| Simply-Coins Ltd | Wholesale & retail | 2023 |
| Simpson Precision Limited | Manufacturing | 2012 |
| Simpsons (Potters) Limited | Manufacturing | 1904 |
| Simtash Limited | Health & social care | 2020 |
| Sindu Mahal Ltd | Manufacturing | 2023 |
| Singh Connection Ltd | Wholesale & retail | 2022 |
| Singularity Engineering Limited | Professional & scientific | 2025 |
| Sinrgy Ltd | Wholesale & retail | 2022 |
| Sinz Tattoo and Piercing Studio Ltd | Other services | 2025 |
| SIP Chai Ltd | Wholesale & retail | 2024 |
| Sipssocial Limited | Hospitality | 2025 |
| Siren Property Limited | Real estate | 2011 |
| Siri Convenience & Spirits Ltd | Wholesale & retail | 2024 |
| Siriv Limited | Real estate | 2021 |
| Siromanii Limited | Wholesale & retail | 2024 |
| Sirri Care Ltd | Health & social care | 2023 |
| Sirrom Properties Ltd | Real estate | 2024 |
| Sista Hair and Beauty Limited | Other services | 2021 |
| Sisu Outdoor Limited | Wholesale & retail | 2026 |
| Site Engineering & Management Solutions Ltd | Real estate | 2023 |
| Site Engineering Services Limited | Professional & scientific | 2018 |
| Site Supplies & Distribution Limited | Wholesale & retail | 2025 |
| Siteality Limited | Extraterritorial | 2008 |
| Sitio Group Ltd | Information & communication | 2026 |
| SIX Retro Limited | Wholesale & retail | 2025 |
| SIX Towns Care Services Ltd | Health & social care | 2026 |
| SIX Towns Catering Supplies Limited | Manufacturing | 2015 |
| SIX Towns Consulting Ltd | Professional & scientific | 2026 |
| SIX Towns Developments Limited | Real estate | 2025 |
| SIX Towns Logs Ltd | Wholesale & retail | 2023 |
| SIX Towns Refrigeration Ltd | Manufacturing | 2021 |
| SIX Towns Sandwich Company Limited | Hospitality | 2023 |
| SIX Towns Services CIC | Administrative & support | 2026 |
| SIX Towns Sport & Community C.I.C. | Education | 2025 |
| Sixtowns Safety Limited | Administrative & support | 2015 |
| Sixtowns Waste Ltd | Water & waste | 2023 |
| Sizzlers Kidsgrove Ltd | Hospitality | 2026 |
| Sizzling WOK 2018 Ltd | Hospitality | 2017 |
| SJ Joinery & Building Limited | Construction | 2004 |
| SJ Property Capital Limited | Professional & scientific | 2025 |
| SJ Sargent Limited | Financial services | 2020 |
| SJ Shone Holdings Ltd | Water & waste | 2022 |
| Sj-Homes Property Services Ltd | Households | 2020 |
| SJB Staff Solutions Ltd | Administrative & support | 2025 |
| SJC Renovations Ltd | Construction | 2021 |
| SJF Transport Limited | Administrative & support | 2014 |
| SJH Group (Contractors) Ltd | Construction | 2017 |
| SJL Driveways and Landscaping Limited | Administrative & support | 2020 |
| SJL Staffordshire Ltd | Construction | 2025 |
| SJN Homes Ltd | Real estate | 2026 |
| SJP Group Midlands Limited | Wholesale & retail | 2016 |
| SJS Building Supplies Limited | Wholesale & retail | 1999 |
| SJS Jukes Ltd | Construction | 2011 |
| Sjsth Holdings Ltd | Financial services | 2025 |
| SJV Joinery & Plumbing Ltd | Construction | 2021 |
| SK Chaudhry Ltd | Wholesale & retail | 2025 |
| SK Foods & Sons Ltd | Wholesale & retail | 2024 |
| SK Properties Holding Ltd | Real estate | 2023 |
| Sk&Mm Ltd | Wholesale & retail | 2025 |
| Skadhor Limited | Financial services | 2023 |
| Skandar-Sabre Limited | Health & social care | 2022 |
| Skandtec Limited | Professional & scientific | 2013 |
| SKB Europe Limited | Extraterritorial | 2019 |
| Skbrian Property Limited | Real estate | 2022 |
| Skelco Limited | Hospitality | 2014 |
| Sketch&Scrach Ltd | Professional & scientific | 2025 |
| Skilled Cleaners First Ltd | Administrative & support | 2025 |
| Skills for Casc Ltd | Education | 2022 |
| Skin Matrix Limited | Wholesale & retail | 2010 |
| Skin Pixel Ltd | Wholesale & retail | 2024 |
| Skin Sanctuary - Skin Body Wellness Limited | Other services | 2022 |
| Skinbase Group Limited | Financial services | 2022 |
| Skins Wear Ltd | Wholesale & retail | 2021 |