| SJC Retail Ltd | Wholesale & retail | 2020 |
| SJG Window Controls Ltd | Manufacturing | 2012 |
| SJK Trading Limited | Wholesale & retail | 2021 |
| SJM Maintenance Ltd | Construction | 2019 |
| SJR Groundworks & Landscaping Ltd | Construction | 2026 |
| SK Transport Services Limited | Transport & logistics | 2019 |
| SKC Interiors Ltd | Construction | 2019 |
| Skdl Invests Ltd | Financial services | 2026 |
| Skills MAX Limited | Education | 2012 |
| Skin & Scent Ltd | Wholesale & retail | 2026 |
| Skin Beauty Limited | Wholesale & retail | 2024 |
| SKR Fashion Ltd | Wholesale & retail | 2025 |
| Sky 8 Takeaway Limited | Hospitality | 2022 |
| Sky Cloud Foods Limited | Hospitality | 2022 |
| Sky Heights General Building and Landscaping Ltd | Construction | 2025 |
| Sky Online Shopping Ltd | Wholesale & retail | 2017 |
| Skyend Holdings Limited | Real estate | 2018 |
| Skyglow Pet Supplies Limited | Wholesale & retail | 2025 |
| Skyline Core Holding Ltd | Real estate | 2026 |
| Skyline Hire Ltd | Administrative & support | 2005 |
| SL and AL Properties Limited | Households | 2025 |
| SL Catering Luton Limited | Hospitality | 2018 |
| Sleepy FOX Cards Ltd | Wholesale & retail | 2025 |
| Slemani Properties Limited | Real estate | 2020 |
| SLJ Homes Ltd | Construction | 2020 |
| SLV Lighting UK Limited | Wholesale & retail | 2018 |
| SM Contract Solutions Ltd | Administrative & support | 2025 |
| SM Dream Limited | Transport & logistics | 2023 |
| SM Reilly & SON Limited | Construction | 2010 |
| SM Retail Limited | Wholesale & retail | 2013 |
| Smart Auto Group Ltd | Financial services | 2024 |
| Smart Automotive East Ltd | Wholesale & retail | 2025 |
| Smart Automotive MK Ltd | Wholesale & retail | 2024 |
| Smart Automotive West Ltd | Wholesale & retail | 2025 |
| Smart Bedroom Solutions Ltd | Construction | 2023 |
| Smart Design Joinery Ltd | Manufacturing | 2021 |
| Smart Investment Pro Limited | Other services | 2025 |
| Smart Simple Properties Limited | Real estate | 2022 |
| Smart Skin Solutions Limited | Health & social care | 2014 |
| Smart Solutions Building & Civil Engineering Ltd | Construction | 2023 |
| Smart Tech UK Trading Ltd | Wholesale & retail | 2026 |
| Smart Touch (MK) Ltd | Wholesale & retail | 2007 |
| Smarteez Limited | Professional & scientific | 2010 |
| Smarter Ohba Leaf Ltd | Hospitality | 2023 |
| Smarter Solutions (Car Cosmetics) Limited | Wholesale & retail | 2006 |
| SMB Restoration Ltd | Construction | 2015 |
| SMC Garage Ltd | Other services | 2010 |
| SMC Travels Limited | Administrative & support | 2024 |
| SMK Communications Limited | Information & communication | 2024 |
| Smooth Care Agency Ltd | Administrative & support | 2023 |
| Snap PCF CIC | Education | 2017 |
| Snowholme Limited | Households | 1995 |
| SO I SEE Limited | Information & communication | 2019 |
| SO Rude Club Limited | Wholesale & retail | 2022 |
| Soap Flower Happiness Ltd | Wholesale & retail | 2023 |
| Soar International Limited | Professional & scientific | 2023 |
| Socialworkbridging Ltd | Health & social care | 2023 |
| Socrates Services Limited | Wholesale & retail | 1989 |
| Soda Social Limited | Administrative & support | 2016 |
| Soho 21 Limited | Hospitality | 2024 |
| Soho Bridge Limited | Hospitality | 2023 |
| SOL Electrical and More Ltd | Construction | 2022 |
| Solar&Sparkselectrical Ltd | Construction | 2026 |
| Sole Movers Ltd | Water & waste | 2021 |
| Solescu Ltd | Transport & logistics | 2019 |
| Solid Green UK Limited | Health & social care | 2018 |
| Solid Linc Ltd | Administrative & support | 2015 |
| Solid Linc Recruitment Limited | Administrative & support | 2018 |
| Solid Syndicate Ltd | Transport & logistics | 2025 |
| Solidpropertydeals Limited | Construction | 2022 |
| Solir Limited | Transport & logistics | 2020 |
| Solo Cycles Limited | Manufacturing | 2011 |
| Solo Design Limited | Administrative & support | 2013 |
| Soltin Properties Ltd | Real estate | 2022 |
| Solutions a+ Ltd | Information & communication | 2021 |
| Solutions Platforms Limited | Administrative & support | 2022 |
| Somachi Limited | Information & communication | 2016 |
| Some New RT Ltd | Financial services | 2014 |
| Someries Luton Limited | Hospitality | 2020 |
| Sonism International Ltd | Wholesale & retail | 2022 |
| Sonnie Limited | Real estate | 2018 |
| Sons & Co Asset Management Ltd | Professional & scientific | 2022 |
| Sons & Co Holdings Limited | Construction | 2025 |
| Sons and Co (2020) Limited | Real estate | 2020 |
| Sons and Company London Limited | Construction | 2023 |
| Sophia Karis Management & Consultancy Ltd | Administrative & support | 2012 |
| Sophie Stokes Ltd | Other services | 2025 |
| SOR Trans LOG Limited | Transport & logistics | 2017 |
| Sorted Counselling Services | Other services | 2010 |
| Sound and Air Tests Ltd | Construction | 2023 |
| Sourcasa Ltd | Manufacturing | 2026 |
| Sourceright Services Limited | Information & communication | 2007 |
| South Beds Heating Ltd | Construction | 2022 |
| South Beds Roofing Ltd | Construction | 2025 |
| South East Direct Waste Solutions Ltd | Water & waste | 2024 |
| South Ruislip Garage Ltd | Wholesale & retail | 2024 |
| Southend Cottage Limited | Hospitality | 2014 |
| Southern Fire Projects Ltd | Construction | 2020 |
| Southwestretreats Ltd | Hospitality | 2025 |
| SOW Green Limited | Administrative & support | 2025 |