| Speak Technologies Ltd | Information & communication | 2024 |
| Speak UP Projects CIC | Arts & recreation | 2025 |
| Spear Concrete Services Ltd | Construction | 2018 |
| Specialist Concierge Ltd | Administrative & support | 2022 |
| Specialist Private Wealth Limited | Financial services | 2002 |
| Specialty Chemicals UK Limited | Wholesale & retail | 2002 |
| Speed Army Ltd | Wholesale & retail | 2021 |
| Speed in Sport Ltd | Wholesale & retail | 2019 |
| Spencer Williams Limited | Real estate | 2018 |
| Spendtastic Limited | Information & communication | 2024 |
| Sphere Consultancy Ltd | Professional & scientific | 2023 |
| Sphinx Ophthalmic Ltd | Health & social care | 2019 |
| SPI Solutions Ltd | Information & communication | 2025 |
| Spice Klub Ruislip Ltd | Hospitality | 2026 |
| Spirit Code Limited | Professional & scientific | 2025 |
| Spiritual Journey Healing Limited | Health & social care | 2020 |
| Spitfire Inbound Ltd | Professional & scientific | 2019 |
| Spjm Construction Ltd | Construction | 2025 |
| Spll Limited | Wholesale & retail | 2023 |
| Spoilt Rotten Ltd | Other services | 2014 |
| Sport UK Limited | Administrative & support | 2007 |
| Sportainment Media Ltd | Arts & recreation | 2024 |
| Sportzcorp Ltd | Information & communication | 2018 |
| Spotless Gutter Cleans Limited | Administrative & support | 2024 |
| Spotty Dog Stories Limited | Wholesale & retail | 2025 |
| Sproughton Ltd | Real estate | 2020 |
| Sproull & Co. Limited | Professional & scientific | 2012 |
| Sproull Taxation Services Limited | Professional & scientific | 2011 |
| SPS Solutions Ltd | Information & communication | 2015 |
| SPV Outsourcing Ltd | Wholesale & retail | 2020 |
| SQA Agile Limited | Information & communication | 2013 |
| Sqale Ltd | Information & communication | 2018 |
| SR Precision Engineering Limited | Manufacturing | 2024 |
| Srishtichhavi Properties Limited | Real estate | 2025 |
| SRK Capital LLP | | 2018 |
| SRK Prescribing Ltd | Health & social care | 2024 |
| SRR Logistics Ltd | Transport & logistics | 2024 |
| SSE Healthcare Limited | Health & social care | 2018 |
| SSE Investments Ltd | Financial services | 2025 |
| SSE Property Services Limited | Real estate | 2023 |
| SSG Enterprise Limited | Wholesale & retail | 2026 |
| Ssml Commercial Ltd | Real estate | 2024 |
| Ssml Dental Ltd | Health & social care | 2025 |
| Ssml Limited | Real estate | 2021 |
| Sssy Holdings Ltd | Real estate | 2020 |
| ST George MOT & Service Center Ltd | Wholesale & retail | 2026 |
| ST Interim Services Ltd | Professional & scientific | 2018 |
| ST Margaret's Beauty Salon Ltd | Other services | 2023 |
| ST Margaret's Wines Limited | Wholesale & retail | 2014 |
| ST Yeghiche Armenian Church Parish Ltd | Other services | 2014 |
| ST. Margarets Property Ltd | Real estate | 2024 |
| ST. Mary and ST. Bishoy Charity Ltd | Other services | 2004 |
| Stair Nosing LLP | | 2017 |
| Stak Portal Ltd | Administrative & support | 2016 |
| Staley Radford & Co. Limited | Transport & logistics | 1927 |
| Stanley's Roofing & Building Limited | Construction | 2015 |
| Stanwell Construction Ltd | Construction | 2022 |
| Staq Technologies Ltd | Information & communication | 2022 |
| Star Blade Ltd | Manufacturing | 2015 |
| Star Care Team Ltd | Administrative & support | 2019 |
| Star Certification UK Ltd | Professional & scientific | 2021 |
| Star Marketing & Distribution Limited | Wholesale & retail | 2012 |
| Staravis Limited | Arts & recreation | 1992 |
| Stardust Education Limited | Education | 2025 |
| Starled Consulting Ltd | Professional & scientific | 2015 |
| Starling Management Limited | Administrative & support | 2011 |
| Starlyte Stays Ltd | Administrative & support | 2026 |
| Starlytehomes Ltd | Real estate | 2021 |
| Staropt Supply Chain Co., Ltd | Administrative & support | 2024 |
| Starway Consulting Ltd | Information & communication | 2014 |
| Stat Network Ltd | Arts & recreation | 2024 |
| Static Electrical Services Limited | Construction | 2014 |
| Status Insurance Management Limited | Financial services | 1984 |
| Steelcore Alliance LLP | | 2004 |
| Stellar Houses Limited | Real estate | 2007 |
| Stepping Stones Nursery Pembury Ltd | Health & social care | 2023 |
| Sterling Alpha Limited | Financial services | 2021 |
| Sterling Flooring Ltd | Construction | 2018 |
| Steve Baker Limited | Health & social care | 2010 |
| Stewart Management & Planning Solutions Limited | Professional & scientific | 2002 |
| STH Traders Limited | Wholesale & retail | 2026 |
| Stirling Family Limited | Real estate | 2016 |
| Stirling Technology Limited | Information & communication | 2018 |
| Stmms Limited | Real estate | 2026 |
| Stokes Home Rentals Ltd | Real estate | 2025 |
| Stolk Steel Limited | Wholesale & retail | 2024 |
| Stonebase Paving Limited | Construction | 2006 |
| Stonefield Way Management Company Limited | Real estate | 2004 |
| Stoneguard (Scotland) Limited | Wholesale & retail | 2000 |
| Stonehead Holdings Ltd | Real estate | 2024 |
| Storage Boost Holdings Limited | Administrative & support | 2007 |
| Storage Boost Ltd | Other services | 2008 |
| Storage King Limited | Wholesale & retail | 2007 |
| Storemore Self Storage Limited | Other services | 2013 |
| Stork Motors Ltd | Wholesale & retail | 2024 |
| Storm Glow Ltd | Other services | 2025 |
| Storm Lounge Ltd | Hospitality | 2024 |
| Storm Stable Construction Ltd | Administrative & support | 2024 |
| Stormforce Roofing Solutions Ltd | Construction | 2022 |
| Stormgrey Consulting Ltd | Information & communication | 2025 |