| SL Engineering Surveys Limited | Professional & scientific | 2013 |
| SLA Engineering Services Limited | Construction | 2007 |
| Slater Conservation Limited | Construction | 2022 |
| Slater Michael Limited | Professional & scientific | 2007 |
| Slatters Building Services Ltd | Construction | 2025 |
| Slaws Electrical Ltd | Construction | 2022 |
| SLC Financial Services Limited | Professional & scientific | 2012 |
| Sleaps Commercials Ltd | Wholesale & retail | 2019 |
| Sleep Restore UK Ltd | Manufacturing | 2026 |
| SLH Trading Limited | Wholesale & retail | 1991 |
| Slipform Engineering Group Ltd | Professional & scientific | 2022 |
| Slipform Engineering Ltd | Manufacturing | 2012 |
| SLK Homes and Design Limited | Construction | 2017 |
| Slkz Limited | Wholesale & retail | 2023 |
| Slock Ltd. | Information & communication | 2012 |
| Slow Down Move Over UK Limited | Other services | 2018 |
| SLP Event Hire Limited | Other services | 2020 |
| Slre Construction Limited | Construction | 2016 |
| SM Arrowsmith Consulting Ltd | Professional & scientific | 2025 |
| SM Gadgets Limited | Wholesale & retail | 2025 |
| SM Minibus Ltd | Transport & logistics | 2023 |
| SM Performance Ltd | Wholesale & retail | 2022 |
| SM Plumbing and Property Services Ltd | Construction | 2020 |
| Smart Facades Ltd | Construction | 2018 |
| Smart Lighting & Electrical Ltd | Manufacturing | 2024 |
| Smart Line Electrical Services Limited | Construction | 2014 |
| Smart Mortgage Solutions Limited | Financial services | 2015 |
| Smart Skills Services Limited | Education | 2025 |
| Smart Sparks Electrical Ltd | Construction | 2018 |
| Smart Style Roofing & Building Ltd | Construction | 2025 |
| Smart Supermarket Ltd | Wholesale & retail | 2026 |
| Smart Worx Ltd | Wholesale & retail | 2021 |
| Smarter Home Improvements Ltd | Construction | 2019 |
| Smartlink Limited | Professional & scientific | 1995 |
| Smartpurse Capital Ltd | Information & communication | 2023 |
| SMB Contracts Ltd | Construction | 2019 |
| SMB Solutions (U.K) Ltd | Construction | 2024 |
| SMD Decorators Limited | Construction | 2015 |
| Smegs Scents Ltd | Manufacturing | 2024 |
| SMG Trans Ltd | Transport & logistics | 2018 |
| Smilecare Hub Ltd | Health & social care | 2026 |
| Smilecleaners Ltd | Administrative & support | 2025 |
| Smiles'N'Cuddles Ltd | Real estate | 2022 |
| Smith & Sons Construction Services Ltd | Construction | 2021 |
| Smith Scaffolding Limited | Construction | 2015 |
| Smith's Hair Limited | Other services | 2017 |
| Smiths Aerospace Limited | Manufacturing | 1964 |
| Smph Limited | Other services | 2025 |
| SMR Capital Ltd | Real estate | 2026 |
| SMR Professional Ltd | Administrative & support | 2013 |
| SMR Site Services Ltd | Construction | 2023 |
| SMS Security Services Ltd. | Other services | 2001 |
| SMT Hire Ltd | Administrative & support | 2018 |
| Snackatizer Ltd | Hospitality | 2018 |
| Snap Happy Babies Limited | Professional & scientific | 2025 |
| SNC Construction (Essex) Ltd | Construction | 2018 |
| Snow SL Ltd | Transport & logistics | 2021 |
| Snowball Design Ltd | Professional & scientific | 2021 |
| SNT Group Limited | Financial services | 2021 |
| SOA Services Ltd | Information & communication | 2025 |
| Soccerdays Chingford Limited | Education | 2023 |
| Soccerdays Epping District Ltd | Education | 2017 |
| Soccerdays Havering Ltd | Education | 2017 |
| Soccerdays Ltd | Professional & scientific | 2015 |
| Soccerdays Redbridge Ltd | Education | 2019 |
| Soccerdays Romford Ltd | Education | 2021 |
| Soccerdays Snaresbrook Ltd | Education | 2017 |
| Soccerdays Waltham Forest Ltd | Professional & scientific | 2019 |
| Soccerdays Woodford Ltd | Education | 2022 |
| Social Value 360 Ltd | Professional & scientific | 2026 |
| Soeva Properties Limited | Real estate | 2023 |
| Sofroni Ltd | Construction | 2016 |
| Softhouse Productions Ltd | Manufacturing | 2023 |
| Softim UK Ltd | Construction | 2019 |
| Softview Gavin Mills Ltd | Construction | 2010 |
| Software Paradise Ltd | Information & communication | 2010 |
| SOJ Limited | Administrative & support | 2014 |
| Sojourn Studios London Ltd | Professional & scientific | 2025 |
| SOL Commercial Ltd | Wholesale & retail | 2024 |
| Solar Energy Rural Electrification Limited | Energy | 2026 |
| Solar Surveying Consultants Ltd | Professional & scientific | 2022 |
| Solarise Ltd | Construction | 2020 |
| Sole Trader Interiors Ltd | Construction | 2025 |
| Solectronix Limited | Information & communication | 2023 |
| Solid Insulated Wall Systems Ltd | Wholesale & retail | 2022 |
| Solidgrain Construction Ltd | Manufacturing | 2026 |
| Solidmate Limited | Administrative & support | 2014 |
| Solnfindaz Ltd | Construction | 2012 |
| Solo Web Solutions Limited | Information & communication | 2004 |
| Solok Ltd | Real estate | 2020 |
| Soltra Group Limited | Wholesale & retail | 2025 |
| Solution Logistics Limited | Construction | 2024 |
| Solution Roofing & Renovations UK Limited | Construction | 2023 |
| Solutions A.W. Ltd | Wholesale & retail | 2019 |
| Solvere Technologies Ltd | Construction | 2021 |
| Somercotes 1960 Limited | Extraterritorial | 2014 |
| Something Borrowed Bridal Ltd | Wholesale & retail | 2020 |
| Sondes Developments Limited | Construction | 2024 |
| Sonic Funding Capital 1 Limited | Financial services | 2024 |
| Sonic Funding Capital 2 Limited | Financial services | 2022 |