| Silent Hand Consulting Limited | Professional & scientific | 2013 |
| Silhouette Events Ltd | Hospitality | 2026 |
| Silmek Ltd | Hospitality | 2020 |
| Silverstone Motorhome and Caravan Servicing Ltd | Wholesale & retail | 2023 |
| SIM 2000 Imaging Ltd | Manufacturing | 2004 |
| Simade Limited | Manufacturing | 2016 |
| Simon Kasziba Health & Safety Services Limited | Construction | 2006 |
| Simon Mason Couriers Limited | Transport & logistics | 2022 |
| Simon Tomkinson Holdings Limited | Financial services | 2021 |
| Simple Bathrooms Ltd | Wholesale & retail | 2018 |
| Simpleynatural Ltd | Administrative & support | 2011 |
| Simply Home Developments Limited | Construction | 2008 |
| Simply Owners Ltd | Information & communication | 2016 |
| Simply Sensory Training and Support Limited | Education | 2022 |
| Simply Ssas Ltd | Administrative & support | 2018 |
| Simply Thoughtful Limited | Health & social care | 2025 |
| Simpson and West Lettings Limited | Real estate | 2015 |
| Sincor Ltd | Transport & logistics | 2018 |
| Singh & Kaur Enterprises Limited | Wholesale & retail | 2019 |
| Sins and Spirits Limited | Hospitality | 2023 |
| Sipson Construction Services Ltd | Construction | 2010 |
| Sipson Property Maintenance Limited | Construction | 2014 |
| Sirlight Ltd | Professional & scientific | 2018 |
| Siteflow Systems Ltd | Information & communication | 2026 |
| Sitta (UK and Ireland) Ltd | Wholesale & retail | 2015 |
| SJ Patel Limited | Real estate | 2025 |
| SJI Designs Limited | Professional & scientific | 2008 |
| SJI Properties Limited | Real estate | 2019 |
| SJM Laralou Estates Limited | Real estate | 2026 |
| SJS Engineering Ltd | Manufacturing | 2002 |
| SK 1 Build Limited | Construction | 2019 |
| SK Contract Flooring Ltd | Construction | 2019 |
| SK Kinsella Limited | Hospitality | 2021 |
| SKD Investment Ltd | Real estate | 2024 |
| Skegness Public Bars Ltd | Hospitality | 2018 |
| Skeldale House Ltd | Real estate | 2018 |
| Skerry Hill Fish Bar Ltd | Hospitality | 2024 |
| SKI and Outdoor Warehouse Limited | Extraterritorial | 1994 |
| Skinner Property Investments Ltd | Real estate | 2017 |
| Skinny Salts Ltd | Wholesale & retail | 2020 |
| Skinplicity Glow Ltd | Other services | 2020 |
| SKN Gears & Components Limited | Manufacturing | 2003 |
| Skyfall Bidco Limited | Extraterritorial | 2021 |
| Skyfall Topco Limited | Extraterritorial | 2020 |
| Skyhigh Haulage Ltd | Transport & logistics | 2024 |
| Skylux Clean Ltd | Administrative & support | 2025 |
| Skyvista Ltd | Information & communication | 2025 |
| SLAWAX77 Ltd | Transport & logistics | 2020 |
| Slawson Associates Limited | Information & communication | 2009 |
| Slec Services Ltd | Construction | 2020 |
| Sline Sanitary Ware Limited | Wholesale & retail | 2024 |
| Slingsby Investco Limited | Financial services | 2020 |
| SM Composite Engineering Ltd | Professional & scientific | 2024 |
| SM Propertyco Ltd | Real estate | 2024 |
| SM Toon Property Ltd | Real estate | 2025 |
| Small Acres Farming Ltd | Agriculture & fishing | 2022 |
| Smart Aluminium Holdings Limited | Financial services | 2019 |
| Smart Aluminium Limited | Manufacturing | 2012 |
| Smart Architectural Coatings Limited | Professional & scientific | 2017 |
| Smart Finch Properties Ltd | Real estate | 2019 |
| Smart Heating Expert Ltd | Construction | 2019 |
| Smart Home Inspections & Clerk of Works Consultants Limited | Construction | 2024 |
| Smart Hops Ltd | Information & communication | 2013 |
| Smart Hughes Solutions Limited | Professional & scientific | 2025 |
| Smartflow Plumbing and Heating Limited | Construction | 2022 |
| Smartpipes Trading Ltd | Wholesale & retail | 2014 |
| SMG Customs Consultant Ltd | Professional & scientific | 2021 |
| SMG Joinery Ltd | Construction | 2019 |
| Smith & Co. Estates Limited | Real estate | 2013 |
| Smith Freight Limited | Transport & logistics | 2025 |
| Smith M SOT Limited | Wholesale & retail | 2006 |
| SMK Lally Limited | Real estate | 2022 |
| Smoke Hayes Limited | Hospitality | 2024 |
| Smpm Consulting Limited | Professional & scientific | 2023 |
| SMS Electro-Tech (Mansfield) Limited | Construction | 2010 |
| Snapdragon TAI CHI Limited | Arts & recreation | 2007 |
| Snappy Host Ltd | Information & communication | 2020 |
| SNB Roofing and Construction Ltd. | Construction | 2018 |
| Sneinton Stop'N'Shop Ltd | Wholesale & retail | 2022 |
| SNK Group Ltd | Financial services | 2018 |
| Snowco Limited | Professional & scientific | 1987 |
| Snowies Books Ltd | Wholesale & retail | 2020 |
| SO Stuffed Ltd | Hospitality | 2025 |
| Society of Teachers of Speech and Drama (the) | Other services | 1944 |
| Sodental Business Consultancy Ltd | Professional & scientific | 2019 |
| Sofianna Limited | Hospitality | 2022 |
| Soft Car Wash Ltd | Wholesale & retail | 2025 |
| Soho Psychology London Ltd | Health & social care | 2024 |
| SOL Trade & Design Ltd | Construction | 2024 |
| Solaris Corporation Limited | Real estate | 2019 |
| Solid C Ltd | Professional & scientific | 2024 |
| Solid Ground Developments Ltd | Construction | 2025 |
| Solid Worktop Studio Ltd | Construction | 2019 |
| Solidaire Property Limited | Real estate | 2025 |
| Solidaire Security Limited | Administrative & support | 2017 |
| Solisair Ltd | Construction | 2007 |
| Somerby Outdoor Cleaners Ltd | Administrative & support | 2021 |
| Somos Solutions Ltd | Other services | 2019 |
| Sonik Smart Services Ltd | Administrative & support | 2022 |
| SOS Electrical Services Ltd | Construction | 2019 |