| River View Residents Management Company Limited | Households | 2018 |
| RL Haulage & Plant Hire Limited | Transport & logistics | 2013 |
| ROB Moore Limited | Administrative & support | 2006 |
| Robust Approvals Limited | Professional & scientific | 2018 |
| Rockfield Property Management Ltd | Real estate | 2024 |
| Rogiet Consultants Ltd | Professional & scientific | 2026 |
| Rogiet Rentals Ltd | Real estate | 2024 |
| Roha International Holding Limited | Financial services | 2024 |
| Rose Style DE VIE Ltd | Wholesale & retail | 2018 |
| Rosie's Bar Limited | Hospitality | 2023 |
| Rosslyn Associates South Wales Ltd | Administrative & support | 2011 |
| Rpex Ltd | Construction | 2026 |
| RST Taxis Monmouthshire Limited | Transport & logistics | 2021 |
| RT & J Lewis Limited | Construction | 2011 |
| Runo & Sons Limited | Real estate | 2023 |
| Runston Ltd | Extraterritorial | 2024 |
| S & a Management Limited | Professional & scientific | 2008 |
| S Devi & Co Limited | Real estate | 2024 |
| S Tech Electrical Services Ltd | Construction | 2025 |
| S&D Williams Properties Ltd | Real estate | 2023 |
| S&T Tanner Ltd | Transport & logistics | 2019 |
| S.I.A. Security and Facilities Management Ltd | Administrative & support | 2010 |
| S.I.M. Design Associates Limited | Wholesale & retail | 1996 |
| Sada Enterprise Ltd | Real estate | 2017 |
| SAM Jones Holdings Limited | Financial services | 2022 |
| Sanctum & Sage Ltd | Hospitality | 2025 |
| Sand Separation Systems Limited | Administrative & support | 2017 |
| Sarbin Solutions Limited | Professional & scientific | 2003 |
| Savigear Martial Arts Ltd | Arts & recreation | 2019 |
| Sayan Enterprise Limited | Wholesale & retail | 2017 |
| Sayan Properties Ltd | Real estate | 2024 |
| SB Moca Ltd | Other services | 2025 |
| SEL Enterprises Limited | Extraterritorial | 2015 |
| Sensemaster Limited | Wholesale & retail | 1984 |
| SERVICES1H Limited | Wholesale & retail | 2023 |
| SERVICES1I Limited | Education | 2023 |
| SERVICES1N Limited | Education | 2023 |
| SERVICES2I Limited | Transport & logistics | 2023 |
| Severn Estuary Investments Limited | Financial services | 2026 |
| Severn Estuary Investments Wealth Limited | Wholesale & retail | 1996 |
| Severn Systems Ltd | Professional & scientific | 2025 |
| Severnbridges Limited | Professional & scientific | 2007 |
| Severnside Sports Coaching Ltd | Arts & recreation | 2022 |
| Shengxin International Ltd | Wholesale & retail | 2024 |
| Shredz City Ltd | Arts & recreation | 2019 |
| Signature Sean Horler Ltd | Construction | 2002 |
| Silures Scientific Limited | Professional & scientific | 2023 |
| Silurian Accounting Ltd | Professional & scientific | 2024 |
| Silver Dollar Estates Limited | Extraterritorial | 2003 |
| Silver Kraft Ltd | Wholesale & retail | 2010 |
| Simaxell Holdings Limited | Households | 2026 |
| Simpsons (UK) Limited | Manufacturing | 2001 |
| Singanayagam Private Lung Ltd | Health & social care | 2025 |
| SJ Driver Training Ltd | Education | 2025 |
| SL Winter Consultancy Ltd | Real estate | 2024 |
| SLA Consultancy Ltd | Wholesale & retail | 2020 |
| Slammin' Acorn Props Ltd | Information & communication | 2022 |
| Smart Choice Developments Ltd | Real estate | 2023 |
| Smart Design Studio Ltd | Arts & recreation | 2014 |
| Smartrenew Ltd | Manufacturing | 2024 |
| Smondays Workshops CIC | Manufacturing | 2025 |
| Solent Care Ltd | Other services | 2016 |
| Solseal Limited | Construction | 1985 |
| Solus Communications Ltd | Information & communication | 2019 |
| Solutions AB Initio Limited | Real estate | 2006 |
| Solve Score Ltd. | Professional & scientific | 2026 |
| Solvique Ltd | Real estate | 2026 |
| Something Borrowed Event Hire Ltd | Hospitality | 2018 |
| Soundhireaudio Ltd | Administrative & support | 2023 |
| South Wales Sports Ground Contractors Limited | Construction | 1964 |
| Sparrowhawk Holdings Limited | Real estate | 2020 |
| SPD Delivery Ltd | Transport & logistics | 2024 |
| Spinnaker Travel Limited | Transport & logistics | 2018 |
| Sporting Connections International Ltd | Professional & scientific | 2025 |
| Sporting Wales Media Limited | Professional & scientific | 2012 |
| Sports Sustenance Ltd | Education | 2019 |
| SPT Services Ltd | Manufacturing | 2020 |
| Squeaky Clean Solutions Ltd | Administrative & support | 2025 |
| Srgh Rail Limited | Construction | 2016 |
| SRK Investments Limited | Real estate | 2007 |
| SRM Business Finance Ltd | Financial services | 2023 |
| ST Mary's Garden Village Limited | Households | 2019 |
| ST Nicholas Residents Management Company Ltd | Households | 2016 |
| ST Tathans Limited | Extraterritorial | 2026 |
| Staddon Photography Ltd. | Professional & scientific | 2018 |
| Standard AI Solutions Ltd | Professional & scientific | 2024 |
| Stanluc Ltd | Wholesale & retail | 2025 |
| Stappert UK Limited | Wholesale & retail | 1979 |
| Star Living Group Ltd | Construction | 2026 |
| Star WOK Newport Limited | Hospitality | 2025 |
| Starkie Sports Performance Limited | Arts & recreation | 2021 |
| Static Dynamic Ltd | Professional & scientific | 2020 |
| Stats Adar Ltd | Professional & scientific | 2019 |
| Steampunk DOT Global Limited | Wholesale & retail | 2015 |
| Steve Harrison Property Ltd | Administrative & support | 2009 |
| Stone & Symmetry Ltd | Professional & scientific | 2025 |
| Stoplight Safety Services Ltd | Professional & scientific | 2017 |
| Strut Fertility Ltd | Professional & scientific | 2025 |
| Stuart Cochrane Heating Ltd | Construction | 2008 |
| Sun Freight International Ltd | Transport & logistics | 2021 |