| RS AK Skin & Aesthetics Clinic Ltd | Health & social care | 2026 |
| RS Physiotherapy & Acupuncture Ltd | Health & social care | 2026 |
| Rubus Scientific Limited | Professional & scientific | 2017 |
| Ruby Rhino Limited | Arts & recreation | 2025 |
| Rudd Profiling Services Ltd | Manufacturing | 2018 |
| Ruko Kebab House Ltd | Hospitality | 2026 |
| Ryan Davies Haulage Limited | Transport & logistics | 2008 |
| Rygbi Nantgaredig Cyfyngedig | Arts & recreation | 2023 |
| Ryze Management Limited | Professional & scientific | 2023 |
| S & a Davies & Daughters Limited | Agriculture & fishing | 2006 |
| S & a Developments (Cymru) Limited | Construction | 2013 |
| S Evans Watercoolers Ltd | Hospitality | 2023 |
| S J Construction (Gwili) Limited | Construction | 2002 |
| S John Bespoke Designs Ltd | Manufacturing | 2024 |
| S Jones & Sons Ltd | Transport & logistics | 2015 |
| S L H Transport Ltd | Administrative & support | 2023 |
| S Rogers Engineering Ltd | Wholesale & retail | 2025 |
| S S James Ltd | Financial services | 2024 |
| S Taylor Trading Ltd | Wholesale & retail | 2024 |
| S Wright Blade Services Ltd | Manufacturing | 2024 |
| S&K Car Transportation Ltd | Transport & logistics | 2019 |
| S. Thomas & SON (Talog) Limited | Transport & logistics | 2003 |
| S.L. George Limited | Professional & scientific | 2011 |
| S.S Pubs SW Ltd | Hospitality | 2025 |
| S4C Digital Media Limited | Information & communication | 1997 |
| S4C Masnachol CYF | Information & communication | 1997 |
| S4C PTG Cyfyngedig | Real estate | 2019 |
| S4C Rhyngwladol CYF | Information & communication | 1998 |
| S4C2 CYF. | Information & communication | 1999 |
| Sage Energy Systems Ltd | Professional & scientific | 2021 |
| Salem Construction Limited | Construction | 1998 |
| Salem Properties Limited | Real estate | 2004 |
| Sally Harmer Animal Health Consultancy Ltd | Professional & scientific | 2017 |
| Samyarh Ltd | Real estate | 2021 |
| Sancler 2 Ltd | Construction | 2009 |
| Sancler 3 Ltd | Construction | 2009 |
| Sancler Solutions Limited | Information & communication | 2012 |
| Sandy Kiln Farms Limited | Agriculture & fishing | 2002 |
| Santa Clara ST Clears Ltd | Hospitality | 2021 |
| Sard Organisation Limited | Financial services | 2020 |
| Sardasht I Ltd | Real estate | 2024 |
| Sarge Cars Ltd | Transport & logistics | 2018 |
| Sarnau Motors Limited | Wholesale & retail | 2021 |
| Sauro Architectural Design Limited | Professional & scientific | 2012 |
| Sazani Research and Development Ltd. | Professional & scientific | 2015 |
| Sbrwaste Limited | Water & waste | 2025 |
| Scaesm Limited | Professional & scientific | 2019 |
| Scaff-Index Limited | Information & communication | 2026 |
| Scanny Property Developments Limited | Real estate | 2026 |
| Scientifeq Ltd | Professional & scientific | 2023 |
| Scott Baker Plumbing & Heating Limited | Construction | 2003 |
| Scott Davis Ltd | Hospitality | 2016 |
| Seaside Essentials Limited | Wholesale & retail | 2013 |
| Seba Systems Ltd | Information & communication | 2005 |
| Security 4 Limited | Administrative & support | 2009 |
| Senlac Ridge Ltd | Information & communication | 2019 |
| Seren Calon Heart Health Ltd | Health & social care | 2026 |
| Seren Dysgu Ltd | Information & communication | 2025 |
| Seren Group Ltd | Financial services | 2022 |
| Seren Vets Ltd | Professional & scientific | 2020 |
| Serenity Garden T/A Serenity Garden (Wales) Limited | Hospitality | 2022 |
| Sero Carmarthenshire CIC | Other services | 2023 |
| Service TOM Ltd | Construction | 2019 |
| Sesee Limited | Professional & scientific | 2021 |
| Setf Ltd | Health & social care | 2018 |
| Sewtech Limited | Wholesale & retail | 2006 |
| SG 23 Ltd | Arts & recreation | 2014 |
| Sgiliau Group HR Ltd | Administrative & support | 2024 |
| Sgiliau Llandeilo CYF | Health & social care | 2022 |
| Sgiliau Llanelli Ltd | Health & social care | 2024 |
| Sgiliau Play Centre Ltd | Health & social care | 2019 |
| Shankari Ltd | Health & social care | 2023 |
| Shareda Limited | Education | 2023 |
| Sharp Plumbing & Heating Limited | Construction | 2013 |
| SHC (Brecon) Ltd | Professional & scientific | 2022 |
| SHD Wynnes Limited | Financial services | 2023 |
| Shift Scaffolding Ltd | Construction | 2024 |
| Siarp Limited | Information & communication | 2020 |
| Signature Paving Limited | Construction | 2026 |
| Silvermere Academy Limited | Arts & recreation | 2016 |
| Silvermere Cafe Limited | Hospitality | 2016 |
| Silverwillowconsultants Ltd | Construction | 2023 |
| Simon Griffiths Builders Ltd | Construction | 2021 |
| Sion James Holdings (Cymru) Ltd | Financial services | 2017 |
| Site Skills Solutions Ltd | Education | 2024 |
| Siôn Charles CYF | Professional & scientific | 2023 |
| SJA Lemur Limited | Education | 2022 |
| SJA MMA Limited | Education | 2022 |
| SJP Consulting & Investigations Ltd | Administrative & support | 2019 |
| Sjrneuropsych Ltd | Professional & scientific | 2024 |
| SJW Designs Ltd | Construction | 2025 |
| SKN Rehab Limited | Wholesale & retail | 2016 |
| Skylas Pawsome Treats Ltd | Wholesale & retail | 2025 |
| Skyrose Connect Limited | Information & communication | 2023 |
| Skysparkle Infinity 888 Ltd | Health & social care | 2023 |
| Slmn Limited | Construction | 2012 |
| Slush CIC | Arts & recreation | 2024 |
| Smart Dough Limited | Manufacturing | 2017 |
| Smart Veterinary Clinic Limited | Professional & scientific | 2007 |
| Smart Veterinary Training Ltd | Professional & scientific | 2022 |