| Scarflo Estates Ltd | Real estate | 2021 |
| Scissor Brothers Limited | Manufacturing | 2008 |
| Scott FPS Ltd | Manufacturing | 2012 |
| Scott Stone Ltd | Manufacturing | 2025 |
| Scotts Hotel Ltd | Hospitality | 1994 |
| Scripta Consult Limited | Information & communication | 2025 |
| SD Vehicle Repairs Limited | Wholesale & retail | 2022 |
| SDD Fast Food Ltd | Hospitality | 2024 |
| SDN Property Limited | Real estate | 2019 |
| Sea Dublew Limited | Construction | 2015 |
| Sea Lane Property Ltd | Real estate | 2018 |
| Searchdog IT Ltd | Information & communication | 2015 |
| Seawashed Brands Limited | Professional & scientific | 2020 |
| Sedgemore Solutions Ltd | Administrative & support | 2022 |
| Seefar Co., Limited | Administrative & support | 2025 |
| Seilwaith Amey Cymru / Amey Infrastructure Wales Limited | Transport & logistics | 2018 |
| Sellen Properties Ltd | Real estate | 2026 |
| SEO Commercial Cleaning Limited | Administrative & support | 2019 |
| Sepnine Ltd | Wholesale & retail | 2024 |
| Seren IT Consulting Ltd | Information & communication | 2012 |
| Seren Play Inspections Ltd | Professional & scientific | 2024 |
| Seren's Electrical Testing Services Ltd | Construction | 2019 |
| Sereni Seeds UK Limited | Wholesale & retail | 2025 |
| Serenity Healthcare Ltd | Financial services | 2021 |
| Seri Ltd | Hospitality | 2021 |
| Servair Limited | Professional & scientific | 2020 |
| SERVICES360 Limited | Construction | 2004 |
| Servonetic Control Instruments Limited | Manufacturing | 1960 |
| Servotron Instruments Limited | Manufacturing | 1972 |
| Settled IT Cymru Ltd | Arts & recreation | 2022 |
| Seven Blackbirds Ltd | Wholesale & retail | 2025 |
| Seven-Waters Ltd | Hospitality | 2024 |
| Severn DC Ltd | Health & social care | 2023 |
| Severn Road Autos Ltd | Wholesale & retail | 2024 |
| Severn Road Cafe Ltd | Hospitality | 2019 |
| Severnside Finance Company Limited | Real estate | 1967 |
| SF Living Ltd | Hospitality | 2026 |
| Sfxhirecym Ltd | Administrative & support | 2026 |
| Shadow Stabs Ltd | Other services | 2026 |
| Shapla (Wales) Limited | Hospitality | 2011 |
| Shazma Limited | Real estate | 2020 |
| Shelly Murphy Travel Ltd | Administrative & support | 2024 |
| Shenzhen Laiwan Crossborder Limited | Wholesale & retail | 2026 |
| Shenzhen Yihao Technology Co., Ltd | Wholesale & retail | 2024 |
| Shenzhen Yimai Technology Company Limited | Wholesale & retail | 2026 |
| Sherbon Business Solutions Ltd | Professional & scientific | 2025 |
| Shift Ventures Ltd | Information & communication | 2021 |
| Shog Ltd | Hospitality | 2026 |
| Shoukat Stones Ltd | Wholesale & retail | 2025 |
| Shovel DRY Lining Limited | Construction | 2014 |
| Shuangbei Trading Co., Ltd | Wholesale & retail | 2025 |
| Sierra Indigo Limited | Wholesale & retail | 2019 |
| Sierra Storm International Limited | Administrative & support | 2015 |
| Sierra Storm Limited | Administrative & support | 2023 |
| Sildale Properties Limited | Construction | 2000 |
| Silurian Tours Limited | Administrative & support | 2025 |
| Silverdrome Ltd | Information & communication | 2018 |
| Simple Print Solutions Ltd | Manufacturing | 2012 |
| Simplex Innovation Ltd | Information & communication | 2022 |
| Sinolink Innovations Limited | Wholesale & retail | 2024 |
| Siren Recruitment Limited | Administrative & support | 2024 |
| Siupasales Limited | Administrative & support | 2026 |
| SIVANSTAR7 Ltd | Wholesale & retail | 2023 |
| SIX Avenue Holdings Ltd | Real estate | 2024 |
| SJ Foods 14 Ltd | Hospitality | 2024 |
| SJ Tenancies Ltd. | Real estate | 2021 |
| SJC Building Renovations Ltd | Real estate | 2025 |
| SJC Motors (Car Sales) Ltd | Wholesale & retail | 2017 |
| SJC Motors (MOT) Ltd | Wholesale & retail | 2017 |
| SJR Consultancy Limited | Professional & scientific | 2025 |
| SJR Property Holdings Ltd | Real estate | 2021 |
| SJR Property Investments Ltd | Real estate | 2019 |
| SK Shaji Limited | Wholesale & retail | 2019 |
| SKB Beauty Ltd | Other services | 2023 |
| Skillix Ltd | Professional & scientific | 2024 |
| Skips 123 Ltd | Water & waste | 2025 |
| Skyline Crane Division Ltd | Professional & scientific | 2026 |
| Skyline Sports Ltd | Wholesale & retail | 2025 |
| Slaters Building and Electrical Services Ltd | Construction | 2023 |
| SLD Wealth Limited | Financial services | 2023 |
| Slwhcm Ltd | Wholesale & retail | 2025 |
| Smart Signage Limited | Professional & scientific | 2025 |
| Smart Sunbeds UK Limited | Wholesale & retail | 2016 |
| Smartcycle Tech Ltd | Wholesale & retail | 2025 |
| Smith Property Developments Limited | Administrative & support | 2002 |
| Smiths Facades Limited | Construction | 2018 |
| Smiths Motor Co Limited | Wholesale & retail | 2025 |
| Snapita Ltd | Professional & scientific | 2020 |
| Snax Cafe Limited | Hospitality | 2025 |
| Snokco Trading Co., Ltd | Wholesale & retail | 2025 |
| Snowy's Gifts and Home Accessories Limited | Wholesale & retail | 2023 |
| Social Care Consultants Ltd | Professional & scientific | 2008 |
| Soda Cosmetics Ltd | Other services | 2025 |
| Sodetex Limited | Wholesale & retail | 2013 |
| Soggy Doggy Grooming Spa Ltd | Other services | 2023 |
| SOL Tech Groups Ltd | Information & communication | 2025 |
| Solo Rental Properties Limited | Real estate | 2022 |
| Soloman Investments Limited | Financial services | 2011 |
| Sonaeh Ltd | Construction | 2025 |
| Sonicvibe Co., Ltd | Wholesale & retail | 2024 |