| Silver Robin Limited | Financial services | 2026 |
| Silverbrook Investments Limited | Real estate | 2021 |
| Simba Electrical Ltd | Construction | 2020 |
| Simhar Ltd | Information & communication | 2014 |
| Simmonds Construction Ltd | Construction | 2016 |
| Simon Abrahams Editing Limited | Information & communication | 2014 |
| Simple Divine Ltd | Wholesale & retail | 2019 |
| Simply Couriers Limited | Transport & logistics | 2004 |
| Simply Diesels Ltd | Wholesale & retail | 2007 |
| Singh Brothers Construction PVT Ltd Ltd | Construction | 2024 |
| Sinok Energy Ltd | Mining & quarrying | 2018 |
| Sinok Exploration and Production Limited | Mining & quarrying | 2014 |
| Sinok OIL & GAS Ltd | Mining & quarrying | 2018 |
| Siri Clicks Ltd | Professional & scientific | 2026 |
| Sirotech (UK) Limited | Professional & scientific | 2012 |
| SIX Ticks Limited | Information & communication | 2012 |
| Siyaram Parking Limited | Transport & logistics | 2019 |
| SK Laundry Ltd | Other services | 2023 |
| SK Technical Services Limited | Information & communication | 2009 |
| SK Testing Solutions Limited | Information & communication | 2019 |
| Skavin Titans Limited | Wholesale & retail | 2025 |
| Skill Team Central Limited | Construction | 2003 |
| Skyblueriver Ltd | Information & communication | 2026 |
| Skychron Events Limited | Hospitality | 2025 |
| Skycooler Limited | Administrative & support | 2005 |
| Skylark Meadow Limited | Households | 2024 |
| Skyline Chauffeuring Ltd | Transport & logistics | 2023 |
| Skylog Limited | Transport & logistics | 2020 |
| Skyluxe Properties Ltd | Real estate | 2024 |
| Skymile Cargo Limited | Transport & logistics | 2025 |
| Skypian Logistics Ltd | Transport & logistics | 2023 |
| Skyway Haulage Limited | Wholesale & retail | 2025 |
| SL1 Vehicle Hire Limited | Administrative & support | 2015 |
| Slimvision UK Ltd | Professional & scientific | 2022 |
| SLK Management Limited | Hospitality | 2019 |
| Slough Van & Truck Centre Ltd. | Wholesale & retail | 1996 |
| SLV Limited | Transport & logistics | 2020 |
| SLV Maint & Build Ltd | Construction | 2020 |
| Smalls Holdings Ltd | Real estate | 2024 |
| Smart Aero Support Limited | Manufacturing | 2019 |
| Smart Carpet & Vinyl Ltd | Construction | 2022 |
| Smart FIX Garage Ltd | Wholesale & retail | 2025 |
| Smart Moove Limited | Wholesale & retail | 2025 |
| Smart Peptides UK Ltd | Wholesale & retail | 2026 |
| Smart Stairs Fittings Ltd | Construction | 2024 |
| Smart to DO IT Ltd | Construction | 2017 |
| Smartbox Solutions (Somerset) Ltd | Professional & scientific | 2017 |
| Smartec Business Solutions Ltd | Information & communication | 2013 |
| Smash & Clear Demolition & Waste Limited | Water & waste | 2026 |
| Smile of Excellence Ltd | Health & social care | 2015 |
| Smitham Tax Consultancy Limited | Professional & scientific | 1996 |
| SMN KZ11 Ltd | Health & social care | 2024 |
| Smobble Ltd | Wholesale & retail | 2017 |
| Smoke & Mart Ltd | Wholesale & retail | 2025 |
| Smoke and Mart Store Ltd | Wholesale & retail | 2026 |
| Smolo AI Ltd | Information & communication | 2025 |
| SMS Investments London Limited | Real estate | 2022 |
| SMS Investments Stanwell Ltd | Real estate | 2002 |
| SMT Staines Ltd | Real estate | 2024 |
| SO Clear Services Limited | Water & waste | 2022 |
| Soan Chah Ltd | Hospitality | 2024 |
| Sobha Real Estate UK Limited | Professional & scientific | 2018 |
| Social and Local CIC | Professional & scientific | 2011 |
| Socially Chrissie Ltd | Information & communication | 2024 |
| Sofdar Invest Ltd | Real estate | 2026 |
| Soft Circuits Ltd | Information & communication | 2020 |
| Solace Construction Ltd | Construction | 2024 |
| Sold on Ltd | Wholesale & retail | 2025 |
| Soletica Ltd | Administrative & support | 2023 |
| Solid Property Invest Ltd | Real estate | 2018 |
| Somed Ltd | Professional & scientific | 2019 |
| Soni Car Wash Ltd | Other services | 2020 |
| Soni Property Investments Ltd | Real estate | 2024 |
| Sonimedical Limited | Health & social care | 2014 |
| Sophia A1 Ltd | Administrative & support | 2025 |
| Sorrento Construction & Interiors Limited | Extraterritorial | 2013 |
| Sorubio Limited | Information & communication | 2013 |
| Source Data Ltd | Information & communication | 2025 |
| Source Moose Ltd | Manufacturing | 2025 |
| South Queen Construction Ltd | Construction | 2017 |
| Southeby Limited | Real estate | 2005 |
| Southecy Limited | Construction | 2014 |
| Southern Union Sounds Limited | Wholesale & retail | 2013 |
| Southern Union Trading Limited | Professional & scientific | 2013 |
| Sovereign House Residents Company Limited | Households | 1987 |
| Sovereign Sirocco Limited | Wholesale & retail | 1984 |
| Sovl Stone Ltd | Wholesale & retail | 2025 |
| SP & EP Properties Ltd | Real estate | 2026 |
| SP View UK Ltd | Professional & scientific | 2010 |
| Spacebar Studio Limited | Professional & scientific | 2014 |
| Sparsh Solutions Ltd | Administrative & support | 2025 |
| Spartan Mobile Tyres Ltd | Wholesale & retail | 2026 |
| Spear Ventures Limited | Information & communication | 2008 |
| Specfast Limited | Wholesale & retail | 1985 |
| Special Opp’S Ltd | Other services | 2025 |
| Spectrum Surfaces Ltd | Construction | 2025 |
| Specvest Limited | Wholesale & retail | 1985 |
| Specwin Limited | Wholesale & retail | 1984 |
| Speedy Courier Group Ltd | Transport & logistics | 2021 |
| Speedy Sparky Solutions Midlands Limited | Construction | 2025 |