| RM General Services Ltd | Administrative & support | 2011 |
| RN Cooling Ltd | Construction | 2024 |
| RN Investment Group Limited | Real estate | 2025 |
| RNS Autos Commercial Limited | Manufacturing | 2022 |
| RNS Autos Ltd | Wholesale & retail | 2018 |
| RNS Storage Ltd | Transport & logistics | 2018 |
| Robbik Property Limited | Real estate | 1948 |
| Robert D Johnson Funeral Directors Limited | Other services | 2019 |
| Robin a. Williams & Co. Limited | Real estate | 1978 |
| Rock City Music Ltd | Hospitality | 2026 |
| Romanian Organisation for Community Advancement CIC | Education | 2025 |
| Romilly Park Wealth Management Ltd | Financial services | 2018 |
| Romilly Quarter Management Company Ltd | Real estate | 2015 |
| Ronson Haas Ltd | Other services | 2020 |
| Roof Guard Services Ltd | Construction | 2022 |
| Roofing Matters Ltd | Construction | 2014 |
| Roperhurst Limited | Manufacturing | 1976 |
| Roryray Ltd | Real estate | 2025 |
| Roseland Childcare Ltd | Health & social care | 2019 |
| Rosella House RTM Company Limited | Households | 2018 |
| Rosemead Aviaries Ltd | Manufacturing | 2014 |
| Rosepalm Limited | Other services | 2002 |
| Ross Adams Enterprises Ltd | Information & communication | 2021 |
| Rosy Blooming Limited | Wholesale & retail | 2025 |
| Rothley Lodge Dental Care Ltd | Health & social care | 2012 |
| Rothley Lodge Holdings Limited | Financial services | 2021 |
| Roxy 124 Ltd | Real estate | 2023 |
| RP Brown Limited | Administrative & support | 2013 |
| RPH Maintenance Solutions Ltd | Other services | 2018 |
| RR Aesthetic Clinic Limited | Other services | 2020 |
| RS Whitehead Decorators Ltd | Construction | 2018 |
| Rubbertoe Replicas Ltd | Professional & scientific | 2012 |
| Ruckleys Limited | Wholesale & retail | 2013 |
| Rustic Roots Nursery Limited | Health & social care | 2021 |
| RW Garage Doors Ltd | Professional & scientific | 2023 |
| RWF Engineering Limited | Professional & scientific | 2022 |
| S & J Services (Cardiff) Limited | Construction | 2026 |
| S & K Property Investments Limited | Real estate | 2016 |
| S & S ENG. Ltd | Construction | 2014 |
| S J Mayled Ltd | Professional & scientific | 2018 |
| S M Vaughan Limited | Construction | 2026 |
| S R COX Consulting Ltd | Information & communication | 2012 |
| S&A Caterers Ltd | Hospitality | 2025 |
| S&G Contractors Ltd | Construction | 2018 |
| S&Ms Carpets Ltd | Wholesale & retail | 2013 |
| S&S Property SW Ltd | Real estate | 2024 |
| S&S Reddy Properties Ltd | Real estate | 2026 |
| S. & K. Haulage (Glamorgan) Limited | Transport & logistics | 1971 |
| S.D. Rees & SON Limited | Construction | 2004 |
| S.E.M. Services Ltd. | Professional & scientific | 2005 |
| S.I Aviation Limited | Manufacturing | 2022 |
| S2 Training Ltd | Education | 2025 |
| Saab Owners Club of Great Britain Limited (the) | Other services | 1974 |
| Saddle Central Fitting Ltd | Manufacturing | 2025 |
| Saddle Central Security Ltd | Administrative & support | 2025 |
| Safety Critical Plastic Solutions Limited | Professional & scientific | 2023 |
| Safety Security Systems Ltd | Administrative & support | 2022 |
| Safety-Counts Ltd | Education | 2014 |
| Saffron Cafe Barry Ltd | Hospitality | 2025 |
| Sage Roofing Ltd | Construction | 2026 |
| Sahara Play Ltd | Arts & recreation | 2024 |
| SAI Baba Logistics Group Ltd | Transport & logistics | 2023 |
| SAI Shakti Group Ltd | Wholesale & retail | 2025 |
| Saimac Ltd | Wholesale & retail | 2019 |
| Saints Cleaning Solutions Ltd | Households | 2012 |
| Saints Training Group Ltd | Administrative & support | 2024 |
| Saiyan Limited | Wholesale & retail | 2020 |
| Salhab Holdings Limited | Real estate | 2021 |
| Salisbury Acquisitions Limited | Real estate | 2024 |
| Salt & Batter Limited | Hospitality | 2025 |
| Sanctuary Wellbeing Ltd | Other services | 2019 |
| Santiago Consulting Ltd | Information & communication | 2026 |
| Santiago Equity Ltd | Financial services | 2026 |
| Santiago Real Estate Ltd | Real estate | 2026 |
| SAR Lettings Ltd | Real estate | 2024 |
| Sarah KAY Dibble Ltd | Administrative & support | 2017 |
| Sarah's the Greengrocers Ltd | Wholesale & retail | 2021 |
| Saransk Limited | Professional & scientific | 2009 |
| Satdreams Ltd | Hospitality | 2013 |
| Satoshi's Page Ltd | Information & communication | 2020 |
| Saunders Plastering Ltd | Construction | 2013 |
| Savery Entertainment Ltd | Information & communication | 2020 |
| Savery Holdings Ltd | Financial services | 2024 |
| Saxonpine Limited | Professional & scientific | 2013 |
| Saxton Marine Supplies Limited | Manufacturing | 2004 |
| SC Painters Ltd | Construction | 2017 |
| Scalehive Marketing Ltd | Professional & scientific | 2026 |
| Scarlett Investments Ltd | Real estate | 2021 |
| Scievita Ltd | Professional & scientific | 2012 |
| SCN Properties Limited | Administrative & support | 1999 |
| Scoop Barry Limited | Hospitality | 2024 |
| Scoops Barry Island Ltd | Arts & recreation | 2018 |
| Scot Owen Carpentry Company Limited | Construction | 2003 |
| Scratch 2 Smash Ltd | Wholesale & retail | 2017 |
| SD Contractors Ltd | Professional & scientific | 2018 |
| Sea Aerosupport Limited | Professional & scientific | 2008 |
| Seafront Games Limited | Information & communication | 2024 |
| Sealord and Sons Scaffolding Limited | Wholesale & retail | 2008 |
| Seatallan Holdings Limited | Professional & scientific | 2022 |
| Seatallan Limited | Manufacturing | 1995 |