| Sipcoffeeco Ltd | Wholesale & retail | 2024 |
| SIX Ways Car Sales Ltd | Wholesale & retail | 2020 |
| Skinhaus UK Ltd | Other services | 2023 |
| Sky Services Limited | Wholesale & retail | 2016 |
| Skyline PB Ltd | Construction | 2018 |
| Skyline Peakers Limited | Transport & logistics | 2025 |
| Skyview Travel Services Limited | Transport & logistics | 2026 |
| Slam Ventures Ltd | Wholesale & retail | 2021 |
| SLT Couriers Limited | Transport & logistics | 2023 |
| SLT Williams Refurbishments Ltd | Construction | 2022 |
| Smart Moovz Ltd | Transport & logistics | 2025 |
| Smash & Grab Co Limited | Construction | 2025 |
| Smith & Saini Properties Ltd | Real estate | 2023 |
| Snacksphere Hub UK Ltd | Wholesale & retail | 2026 |
| Social Boost Agency Co. Ltd. | Professional & scientific | 2024 |
| Societas Management Ltd | Professional & scientific | 2009 |
| Socratic Strategies Ltd | Professional & scientific | 2024 |
| Solid Gold Limited | Administrative & support | 1979 |
| Solsen CYF. | Construction | 2018 |
| Somnipharm Ltd | Health & social care | 2026 |
| SONEX3 Ltd | Administrative & support | 2014 |
| Sophsvolt Energy Limited | Manufacturing | 2025 |
| Sosban Hospitality Limited | Hospitality | 2020 |
| Sospan Flooring Ltd | Construction | 2025 |
| Sospan Properties Ltd | Real estate | 2020 |
| Sospan Skips Limited | Water & waste | 1999 |
| Sound House Lettings Ltd | Real estate | 2025 |
| Sourbutts Properties Limited | Real estate | 2010 |
| South Kebab Ltd | Hospitality | 2026 |
| South Wales Medical Event Cover Ltd | Health & social care | 2012 |
| South Wales Tree Services Limited | Other services | 2014 |
| South Wales Tyre Recycling Ltd | Water & waste | 2019 |
| South West Groundworks Ltd | Construction | 2025 |
| Southmead Guesthouse Limited | Hospitality | 2007 |
| Space Monkey Creations Ltd | Wholesale & retail | 2018 |
| Space Productions (Distribution) Limited | Information & communication | 1994 |
| Space Productions Limited | Information & communication | 1992 |
| Spacedweller Ltd | Real estate | 2019 |
| Spanglemonkey Ltd | Information & communication | 2018 |
| Sparkle Pro Caravan Cleaning Ltd | Administrative & support | 2020 |
| Specialised Visa Services Ltd | Administrative & support | 2024 |
| Spilman Limited | Construction | 2024 |
| SPL Wales Support Ltd | Administrative & support | 2025 |
| Sporting Classic Marques Ltd | Other services | 2023 |
| Sportouring Limited | Wholesale & retail | 2014 |
| Springwood Lettings Ltd | Real estate | 2020 |
| SRH Plumbing Ltd | Extraterritorial | 2023 |
| SSN Property & Housing Ltd | Construction | 2025 |
| Stadium Wheels Limited | Administrative & support | 2012 |
| Stag Audio Limited | Wholesale & retail | 2015 |
| Station Vape Llanelli Ltd | Wholesale & retail | 2025 |
| Stayt Services Limited | Administrative & support | 2022 |
| Stebonheath Management Ltd | Hospitality | 2016 |
| Steele Waste Removal Ltd | Water & waste | 2025 |
| Steeple Jack Services Limited | Administrative & support | 2019 |
| Steffthomas Limited | Real estate | 2023 |
| Stellar Energy UK Limited | Construction | 2018 |
| Stephen Evans Leisure Ltd | Hospitality | 2018 |
| Steve Ellum & Associates Limited | Professional & scientific | 2003 |
| Steve Garnett Consultancy Ltd | Education | 2014 |
| Steve Ratcliffe Films Limited | Information & communication | 2012 |
| Steven Griffiths Ltd | Agriculture & fishing | 2009 |
| Stitch & Go Ltd | Other services | 2021 |
| Stone & Oak Properties Ltd | Real estate | 2025 |
| Stonebridge Financial Limited | Financial services | 2025 |
| Stonevale Property Limited | Households | 2025 |
| Storicymru CYF | Information & communication | 2019 |
| Storyarcstudios Ltd | Information & communication | 2025 |
| Strade Property Ltd | Real estate | 2025 |
| Stradey Castle Events Limited | Arts & recreation | 2006 |
| Stradey Development Limited | Real estate | 2016 |
| Stradey Memorials Limited | Wholesale & retail | 2011 |
| Stradey Motor Company Ltd | Wholesale & retail | 2020 |
| Stradey Park Care Homes Limited | Health & social care | 2003 |
| Stradey Patio Centre Limited | Wholesale & retail | 2022 |
| Strange Electrics Limited | Construction | 2006 |
| Studio 29 Furniture Ltd | Manufacturing | 2025 |
| Suba Maesgolau Ltd | Wholesale & retail | 2017 |
| Sully Homes Ltd | Real estate | 2026 |
| Summer Weather Limited | Hospitality | 2024 |
| Sundies Ltd | Manufacturing | 2022 |
| Sunnieod Engineering Limited | Construction | 2025 |
| Sunrise 01 Limited | Hospitality | 2025 |
| Sunset & Vine Mobiles Limited | Information & communication | 1987 |
| Sunset & Vine North Limited | Information & communication | 1999 |
| Sunset & Vine Productions Ltd | Information & communication | 1976 |
| Sunset + Vine (London 2017) Limited | Information & communication | 2015 |
| Sunset + Vine (Oxford) Limited | Information & communication | 1999 |
| Sunset + Vine Global Television Host Broadcaster Limited | Information & communication | 2011 |
| Sunset + Vine Limited | Information & communication | 2016 |
| Sunset + Vine Midlands Limited | Information & communication | 2019 |
| Sunshine Support Services Ltd | Health & social care | 2023 |
| Superadpro Ltd | Information & communication | 2026 |
| Superdry-Clean Limited | Administrative & support | 2013 |
| Supersonic Retail Limited | Wholesale & retail | 2017 |
| Support My Cause Limited | Administrative & support | 2025 |
| Support My School Limited | Administrative & support | 2025 |
| Support My Team Ltd | Administrative & support | 2020 |
| Surely Trading Ltd | Wholesale & retail | 2026 |
| Suselt Ltd | Other services | 2024 |