| Savroy First Ltd | Wholesale & retail | 2024 |
| SC Ralley Ltd | Construction | 2025 |
| SCC TH Ltd | Hospitality | 2023 |
| Scout Academy Ltd | Education | 2023 |
| Scout AI Group Ltd | Information & communication | 2025 |
| Scout AI Labs Ltd | Information & communication | 2026 |
| Scout AI Operations Ltd | Information & communication | 2026 |
| Scout AI Talent Ltd | Information & communication | 2026 |
| Scout Consultancy Ltd | Information & communication | 2025 |
| SDJ Decorating Ltd | Construction | 2023 |
| Sean O'Connor Plant Services Limited | Extraterritorial | 2003 |
| Sean O'Connor Site Services Limited | Construction | 2002 |
| Searigsuk Ltd | Wholesale & retail | 2015 |
| Secure Systems Services LLP | | 2022 |
| Security & Identity Solutions Ltd | Wholesale & retail | 2015 |
| Select Housing Limited | Real estate | 2006 |
| Seonaid Butler Rental Portfolio Ltd | Real estate | 2021 |
| Sgrm Ltd | Administrative & support | 2025 |
| Shadwell Maurice Ltd | Wholesale & retail | 2025 |
| Sharkdu Limited | Wholesale & retail | 2025 |
| Sharp Property Development Ltd | Real estate | 2026 |
| Shepphard Properties Limited | Real estate | 2022 |
| Shepphard Property Services Ltd | Real estate | 2025 |
| Shepwood Acres Ltd | Wholesale & retail | 2025 |
| Shetland Lydney Ltd | Wholesale & retail | 2025 |
| Shift Industries Ltd | Transport & logistics | 2024 |
| Shipfield Temples Ltd | Wholesale & retail | 2025 |
| Shoebox Coffee Ltd | Wholesale & retail | 2025 |
| Showlite Holdings Limited | Administrative & support | 2022 |
| Showlite Limited | Administrative & support | 1992 |
| Shrearya Estate Ltd | Real estate | 2025 |
| Shree OIL Ltd | Wholesale & retail | 2012 |
| Shutter & Blind Solutions Ltd | Manufacturing | 2022 |
| Sigasiga Ltd | Other services | 2015 |
| Silverstone Property Limited | Real estate | 2021 |
| Simon Thompsett Associates Limited | Administrative & support | 1985 |
| Sister Coffee Ltd | Manufacturing | 2026 |
| SJ Gleaming Cleans Ltd | Administrative & support | 2024 |
| SJ Holiday LET Management Ltd | Hospitality | 2025 |
| SJC Projects & Services Limited | Manufacturing | 2013 |
| SJJ Operators Ltd | Construction | 2026 |
| Skyvault Data Solutions Ltd | Manufacturing | 2026 |
| SME Active Solutions Ltd | Administrative & support | 2018 |
| Smxoffroad Ltd | Wholesale & retail | 2023 |
| Snappy Picture Limited | Wholesale & retail | 2024 |
| Snow Property Management Limited | Real estate | 2025 |
| Snow White Laundries Limited | Other services | 2000 |
| Snow's Property Limited | Real estate | 2025 |
| Solarrelief Ltd | Energy | 2025 |
| Sorella Property Holdings Limited | Real estate | 2021 |
| Soulport Limited | Extraterritorial | 2001 |
| South Wales Boiler Care Ltd | Construction | 2015 |
| South Wales Colourcoat Limited | Manufacturing | 2023 |
| South Wales Custom Campers Ltd | Manufacturing | 2018 |
| South Wales DRY Lining Limited | Construction | 2019 |
| South Wales Gearboxes and Van Sales Limited | Wholesale & retail | 2006 |
| South Wales Metal Finishing Limited | Manufacturing | 2001 |
| South Wales Properties Ltd | Financial services | 2023 |
| South Wales Removals and Storage Ltd | Transport & logistics | 2025 |
| South Wales Removals Ltd | Transport & logistics | 2010 |
| South Wales Truck and Trailer Limited | Wholesale & retail | 2019 |
| South Wales Walls & Ceilings Ltd | Construction | 2026 |
| Southway Consulting Ltd | Professional & scientific | 2023 |
| Sparkes Property Ltd | Real estate | 2025 |
| SPC Pipe Welding Services Ltd | Manufacturing | 2021 |
| Specialist Approach Services Ltd | Administrative & support | 2021 |
| Spencer Key Properties Ltd | Real estate | 2026 |
| Spencers of Newport Limited | Manufacturing | 2015 |
| Spin Labs Creative Limited | Education | 2023 |
| Sploots Ltd | Wholesale & retail | 2021 |
| Spokes Properties Ltd | Real estate | 2025 |
| Sprowston Walls Ltd | Wholesale & retail | 2025 |
| Spud Inc Ltd | Hospitality | 2024 |
| SRS Floor Coverings Limited | Construction | 2025 |
| SSB Technical Services Ltd | Administrative & support | 2021 |
| SSC Weightlifting CIC | Arts & recreation | 2024 |
| ST Luke’S Premier Ltd | Wholesale & retail | 2018 |
| Stag Security Limited | Administrative & support | 2024 |
| Standing by Film & TV Transport Ltd | Transport & logistics | 2025 |
| Standon Amble Ltd | Wholesale & retail | 2025 |
| Stanley & West Limited | Construction | 2014 |
| Star Kitchen 46 Limited | Hospitality | 2023 |
| Stealth Contractors Limited | Construction | 2014 |
| Stedman Property Investment Ltd | Real estate | 2020 |
| Steed Holdings Limited | Financial services | 2016 |
| Stephens Wilmot Ltd | Professional & scientific | 2016 |
| Steve Padfield Logistics Limited | Transport & logistics | 2018 |
| Steve's Garden Tools and Accessories Limited | Wholesale & retail | 2017 |
| Steven Hanlon Lawncare Ltd. | Administrative & support | 2023 |
| Stockton Cedars Ltd | Wholesale & retail | 2024 |
| Stoian&Tudor Services Ltd | Transport & logistics | 2023 |
| Stonebridge Estate Group Ltd | Real estate | 2026 |
| Strange Industries Limited | Manufacturing | 2020 |
| Strategic I Limited | Professional & scientific | 2013 |
| Strength & Performance Training (Wales) Limited | Arts & recreation | 2009 |
| SU Professionals Ltd | Other services | 2020 |
| Sulli VK Limited | Real estate | 2022 |
| Sundeen Ward Ltd | Wholesale & retail | 2025 |
| Sunny Store UK Ltd | Wholesale & retail | 2022 |
| Sunnyhome Developments Limited | Real estate | 2009 |