| Southwest Kitchen Fitting Ltd | Construction | 2015 |
| Southwest Leisure Activities Ltd. | Arts & recreation | 2016 |
| Southwest Paving Ltd | Construction | 2018 |
| Southwest Pizza & Burger Ltd | Hospitality | 2024 |
| Southwich House RTM Company Ltd | Households | 2015 |
| Sovereign Consulting Ltd | Construction | 2025 |
| Sovereign Guitars Limited | Manufacturing | 2002 |
| Sovereign Merchant Capital Limited | Extraterritorial | 2014 |
| Sovereign Structures Ltd | Construction | 2019 |
| Sovereign Window Fabrication Limited | Manufacturing | 1993 |
| SP Computers (Swindon) Limited | Other services | 2000 |
| SP Pharma Ltd | Professional & scientific | 2013 |
| SP Trans Limited | Transport & logistics | 2016 |
| Space Platform Limited | Administrative & support | 2012 |
| Spanwright UK Limited | Construction | 2010 |
| Sparcells Pharma Ltd | Wholesale & retail | 2011 |
| Spark Films Int’L Ltd | Information & communication | 2025 |
| Spark Retail Limited | Extraterritorial | 2017 |
| Spark Trading Limited | Wholesale & retail | 2020 |
| Sparkkle Couriers Ltd | Transport & logistics | 2025 |
| Sparkle by Jedz Ltd | Administrative & support | 2025 |
| Sparkle Dental Boutique Limited | Health & social care | 2009 |
| Sparkybusiness Ltd | Wholesale & retail | 2024 |
| Sparrow Logistics Ltd | Wholesale & retail | 2018 |
| SPB Sales Limited | Administrative & support | 2025 |
| SPB Swindon Ltd | Construction | 2020 |
| Speak Strength Limited | Wholesale & retail | 2023 |
| Spear Consultancy Limited | Professional & scientific | 2004 |
| Specialist Access Rentals Limited | Construction | 2021 |
| Specialist Coatings & Inspection Ltd | Construction | 2023 |
| Specialist Dental Partners Limited | Health & social care | 2011 |
| Spectrum IT Hub Limited | Information & communication | 2021 |
| Speedy Junior Transport Ltd | Administrative & support | 2014 |
| Spenby Group Ltd | Information & communication | 2013 |
| Speyes Tech Ltd | Information & communication | 2026 |
| Sphike Ltd. | Construction | 2025 |
| SPI Performance Coatings Limited | Manufacturing | 2013 |
| Spice of Africa Catering Ltd | Hospitality | 2026 |
| Spiced Heritage Ltd | Wholesale & retail | 2025 |
| Spicy Tofu Limited | Professional & scientific | 2025 |
| Spinelli Kilcollin UK Ltd | Wholesale & retail | 2024 |
| Spiral Ventures Limited | Extraterritorial | 2019 |
| Spire House Developments Limited | Construction | 2004 |
| Spire House Holdings Limited | Real estate | 2016 |
| Splash Creative Studio Ltd | Information & communication | 2025 |
| Splitstore Ltd | Wholesale & retail | 2024 |
| SPM Property Holdings Limited | Real estate | 2020 |
| SPM Property Management Ltd | Households | 2019 |
| SPM25 Limited | Information & communication | 2025 |
| SPN Capital Limited | Real estate | 2017 |
| Spooner Brothers Ltd | Construction | 2006 |
| Sportamp Ltd | Information & communication | 2025 |
| Sportfreelancers Ltd | Wholesale & retail | 2026 |
| Sporting Excellence Ltd | Arts & recreation | 2019 |
| Sports Entertainment Ltd | Arts & recreation | 2024 |
| Sports Turf Consulting Ltd | Professional & scientific | 2019 |
| Sports X Coaching Ltd | Education | 2023 |
| Spotlights Academy LLP | | 2017 |
| Spotlights Theatre School Limited | Arts & recreation | 2006 |
| SPR Civils Ltd | Construction | 2012 |
| SPR Motor Engineers Limited | Wholesale & retail | 2015 |
| Spray Smart (Swindon) Ltd | Wholesale & retail | 2019 |
| Spray Team Swindon Ltd | Construction | 2024 |
| Spraymaster Limited | Wholesale & retail | 1990 |
| Spraywells Limited | Manufacturing | 2010 |
| Spring Close Management Company Limited | Households | 2022 |
| Spring Heating & Plumbing Limited | Construction | 2002 |
| Springfield Court (Purton) Residents Limited | Real estate | 2004 |
| Springfit Clubs LLP | | 2024 |
| Springpay Ltd | Information & communication | 2024 |
| Sprinkle Property Ltd | Real estate | 2022 |
| Sprint Academy LLP | | 2020 |
| Sprme Food Ltd | Hospitality | 2024 |
| Spruzoo Limited | Administrative & support | 2025 |
| Spudway Swindon Ltd | Hospitality | 2022 |
| Spurson Capital Ltd | Real estate | 2023 |
| SPV Apex Ltd | Real estate | 2025 |
| SPV Consulting (UK) Limited | Information & communication | 2012 |
| Spwc Limited | Arts & recreation | 2026 |
| SPY13 Ltd | Transport & logistics | 2017 |
| Spyglass Technologies UK Ltd | Professional & scientific | 2023 |
| Sqit Limited | Information & communication | 2023 |
| Square Hotel Luton Limited | Real estate | 2022 |
| Squareroot Innovations Ltd | Information & communication | 2025 |
| Squeeze Sports LLP | | 2011 |
| Squinted Ltd | Wholesale & retail | 2025 |
| Squire Property Limited | Construction | 2021 |
| SR Eternal Healthcare Ltd | Health & social care | 2026 |
| SR Moors Limited | Health & social care | 2009 |
| SR Roofing & Guttering Ltd | Construction | 2026 |
| Srcg Consultancy Limited | Information & communication | 2014 |
| Sree SAI9 Limited | Health & social care | 2014 |
| Srgl 11924352 Limited | Administrative & support | 2019 |
| SRH Heating & Homes Ltd | Construction | 2004 |
| SRI ZEN DEN Ltd | Other services | 2023 |
| Srilanka Naturals Ltd | Manufacturing | 2024 |
| Sriraj Limited | Real estate | 2025 |
| Srivi Consulting Ltd | Information & communication | 2011 |
| Srjaar Property Limited | Real estate | 2023 |
| SRM Training Solutions Limited | Professional & scientific | 2015 |