| Suzukikwak Limited | Professional & scientific | 2016 |
| SV Accounts & Bookkeeping Limited | Professional & scientific | 2023 |
| SV IT Development Ltd | Information & communication | 2021 |
| SV Robot Solutions Ltd | Professional & scientific | 2023 |
| Svala Holdings Limited | Real estate | 2003 |
| SVC (South) Ltd | Manufacturing | 2025 |
| SVV Trading Limited | Information & communication | 2011 |
| SW Commerce Ltd. | Wholesale & retail | 2022 |
| SW Global Logistics Ltd. | Transport & logistics | 2015 |
| SW Traffic Solutions Ltd | Professional & scientific | 2013 |
| SWA Building Ltd | Manufacturing | 2024 |
| Swan 21 Ltd | Wholesale & retail | 2019 |
| Swan Capital Nominees Limited | Professional & scientific | 2025 |
| Swan Court (Bursledon) Limited | Real estate | 1977 |
| Swan Estates Limited | Construction | 2003 |
| Swan Morley Ltd | Real estate | 2024 |
| Swan Winterbourne Limited | Hospitality | 2021 |
| Swanlocal Ltd | Wholesale & retail | 2023 |
| Swanmore Business Park Limited | Real estate | 2019 |
| Swanmore Self Store Limited | Administrative & support | 2017 |
| Swanmore SLR Management Ltd | Professional & scientific | 2024 |
| Swannell's Walk Management Company Limited | Real estate | 2015 |
| Swannex Freight Limited | Transport & logistics | 2025 |
| Swanships Limited | Real estate | 2022 |
| Swanside Services Limited | Other services | 2025 |
| Swanton Feeney Property Co Ltd | Real estate | 2025 |
| Swanwick Construction Group Limited | Professional & scientific | 1994 |
| Swanwick Marine Engineers Limited | Other services | 2006 |
| Swanwick Quay Freehold Limited | Other services | 2014 |
| Swanwick Quay Limited | Real estate | 2011 |
| Swanwick, Bursledon and Warsash Regatta | Arts & recreation | 2008 |
| Sway Court Management Limited | Real estate | 1984 |
| Sway Local Limited | Wholesale & retail | 2024 |
| Sway Project Ltd | Construction | 2025 |
| Swaythling Laundry Services Limited | Administrative & support | 2025 |
| Swaythling Management Limited | Households | 2008 |
| Sweepout Ltd | Administrative & support | 2025 |
| Sweet Alloys Limited | Wholesale & retail | 2018 |
| Sweet Boutique Gelato Limited | Manufacturing | 2018 |
| Sweet Days Ltd | Hospitality | 2020 |
| Sweet Encounter Ltd | Wholesale & retail | 2024 |
| Sweet Lunar Ltd | Wholesale & retail | 2023 |
| Sweet Sarcasm Ltd | Wholesale & retail | 2024 |
| Sweet Thoughts (Bournemouth) Ltd | Wholesale & retail | 2008 |
| Sweet Thoughts Limited | Wholesale & retail | 2003 |
| Sweetdreams BED Company Limited | Wholesale & retail | 2006 |
| Sweetpea Florists (Southampton) Limited | Wholesale & retail | 2017 |
| Swete Sailing Ltd | Arts & recreation | 2025 |
| Swift Airgen Limited | Professional & scientific | 2021 |
| Swift Build Properties Ltd | Construction | 2022 |
| Swift Data Cabling Limited | Professional & scientific | 2015 |
| Swift Financial Services Ltd | Financial services | 2017 |
| Swift Homeopathy Clinic Limited | Health & social care | 2024 |
| Swift House Ltd | Construction | 2011 |
| Swiftfix Distributors Limited | Wholesale & retail | 2017 |
| Swiftfix Holdings Limited | Real estate | 2024 |
| Swiftly Removals Ltd | Transport & logistics | 2025 |
| Swiftzers Ltd | Information & communication | 2025 |
| Swiish Cleaning Services Ltd | Administrative & support | 2019 |
| Swim Active UK Ltd | Wholesale & retail | 2025 |
| Swimmable Pools Ltd | Education | 2025 |
| Swinghold Limited | Agriculture & fishing | 1987 |
| Swipe Digital Limited | Information & communication | 2015 |
| Swiss Health Limited | Wholesale & retail | 2003 |
| Swiss Security Limited | Administrative & support | 2024 |
| Swiss UP Ltd | Information & communication | 2025 |
| Switch Club Southampton Limited | Hospitality | 2016 |
| Switch Engineering Limited | Manufacturing | 2014 |
| Switch X Ltd | Professional & scientific | 2025 |
| Switchable Smart Films Ltd | Other services | 2018 |
| Switchnet Services Limited | Information & communication | 2004 |
| SWJ Maintenance Ltd | Construction | 2022 |
| Swlos Limited | Construction | 2019 |
| SWO Consult Ltd | Professional & scientific | 2012 |
| Swow Ltd | Information & communication | 2024 |
| SWP Accountants Limited | Professional & scientific | 2013 |
| SWS Commercials Limited | Wholesale & retail | 2019 |
| Swyft South Coast Limited | Transport & logistics | 2025 |
| Swyre Park Limited | Hospitality | 2022 |
| SY Wiggall Coaching Ltd | Arts & recreation | 2025 |
| Sycamore Services - South Limited | Manufacturing | 2016 |
| Sychem Group Holdings Limited | Manufacturing | 2022 |
| Sychem Limited | Wholesale & retail | 2003 |
| Sychem Surgical Limited | Manufacturing | 2003 |
| SYD UK | Administrative & support | 2001 |
| Syd's Services Limited | Administrative & support | 2024 |
| Sydac Limited | Information & communication | 2006 |
| Syed Rosul Lettings Limited | Households | 2024 |
| Sykes Design Limited | Manufacturing | 2013 |
| Syla Scaffolding Ltd | Construction | 2023 |
| Sylva Cyber & Protection Ltd | Administrative & support | 2026 |
| Sylvie Limited | Wholesale & retail | 2025 |
| Symbiotic Atelier Ltd | Wholesale & retail | 2023 |
| Symetrica Limited | Professional & scientific | 2002 |
| Symetrica Security Ltd | Manufacturing | 2002 |
| Symlaw Management Ltd | Professional & scientific | 2023 |
| Symonds Property & Build Ltd | Construction | 2015 |
| Symphy Holdings Ltd | Wholesale & retail | 2025 |
| Symwick Limited | Manufacturing | 2010 |
| Synaptex Limited | Information & communication | 2011 |