| Smith Bradbeer (Removals) Limited | Professional & scientific | 2000 |
| Smithfield Investments I Limited | Financial services | 2023 |
| Smooth Vapor Limited | Manufacturing | 2019 |
| SMT Orthopaedics Ltd | Health & social care | 2017 |
| Snowdon Management RTM Company Limited | Real estate | 2008 |
| Snstocksolutions Ltd | Wholesale & retail | 2017 |
| SO Young Live Ltd | Arts & recreation | 2025 |
| Soak Rochford Ltd | Manufacturing | 2018 |
| Sofa Smith Ltd | Wholesale & retail | 2018 |
| Sofa Studio (Hampshire) Ltd | Manufacturing | 2011 |
| SOL Polaris Ltd | Extraterritorial | 2023 |
| Solent Choirs Limited | Education | 2021 |
| Solent Gearboxes & Axles Limited | Wholesale & retail | 2017 |
| Solent Sports and Education Ltd | Education | 2022 |
| Solve Holdings Limited | Professional & scientific | 2026 |
| Solve Innovations Ltd | Manufacturing | 2023 |
| Sonnywood Properties Ltd | Real estate | 2026 |
| Sort Your Accounts Hampshire Ltd | Professional & scientific | 2016 |
| Sort Your Accounts Ltd | Professional & scientific | 2017 |
| Soteria Marketing Ltd | Professional & scientific | 2024 |
| Sourcefully Ltd | Administrative & support | 2026 |
| South Coast Caravan Sales Limited | Wholesale & retail | 2009 |
| South Coast Chiropractic Ltd | Health & social care | 2022 |
| South Coast Containers Limited | Professional & scientific | 2008 |
| South Coast Fencing Holdings Limited | Financial services | 2025 |
| South Coast Land Solutions Limited | Construction | 2024 |
| South Coast Spine Clinic Limited | Real estate | 2011 |
| South Hants Building Company Limited | Professional & scientific | 1978 |
| South Home Improvements Ltd | Construction | 2021 |
| South London Music Therapy Limited | Public administration | 2023 |
| South West Investment Partnership LLP | | 2010 |
| Southern Applications Limited | Administrative & support | 2011 |
| Southern Assessors Limited | Professional & scientific | 2023 |
| Southern Contracting Services Limited | Construction | 1997 |
| Southern Engineering & Marine Co Ltd | Manufacturing | 2013 |
| Southern Exhaust Supplies Limited | Professional & scientific | 2001 |
| Southern Medical Legal Services Limited | Health & social care | 2002 |
| Southern Polishing Services Limited | Professional & scientific | 2015 |
| Southern Spinal Services Limited | Health & social care | 2022 |
| Southern Stainless Ltd | Wholesale & retail | 2012 |
| Southern Waterscapes Aquatic Centres Ltd | Wholesale & retail | 2011 |
| Southwest Heart Ltd | Health & social care | 2018 |
| Sovereign Bathrooms Ltd | Construction | 2025 |
| Sozo Ministries International | Other services | 2005 |
| Space Kitchens and Bathrooms Ltd | Construction | 2010 |
| Space Partitioning Ltd | Construction | 2013 |
| Spanfair Limited | Manufacturing | 1987 |
| Spanish Investments Ltd | Financial services | 2020 |
| Spar-Tec Engineering Limited | Manufacturing | 2002 |
| Sparcraft Racing Limited | Manufacturing | 1995 |
| Spark Educational Psychology Ltd | Education | 2026 |
| Sparsh Consulting Limited | Professional & scientific | 2025 |
| SPC Southampton Limited | Real estate | 2006 |
| SPC Southampton Property Ltd | Real estate | 2017 |
| Speaking Space (Romsey) Ltd | Education | 2021 |
| Spear Services Limited | | 1991 |
| Specialised Engineering Products Limited | Manufacturing | 2002 |
| Speedway Developments Limited | Financial services | 2025 |
| Speirs Medical Limited | Health & social care | 2016 |
| Spine Care Consulting LLP | | 2023 |
| Spines Dorset Limited | Health & social care | 2018 |
| Spire Holding Developments Limited | Real estate | 2024 |
| Sport Actif Limited | Arts & recreation | 1989 |
| Sport Healthcare Ltd | Health & social care | 2021 |
| Springall Equestrian Ltd | Arts & recreation | 2022 |
| Springfield House (Romsey) Management Company Limited | Households | 2024 |
| Springstar Technology Limited | Information & communication | 2018 |
| SPW Medical Limited | Health & social care | 2019 |
| Square Networking Limited | Other services | 2019 |
| Srevnad Limited | Real estate | 2026 |
| Srini ABI Ltd | Health & social care | 2015 |
| Srini ABI Properties Ltd | Real estate | 2024 |
| Srinivas Associates Ltd | Health & social care | 2023 |
| SSC Performance Ltd | Education | 2025 |
| SSS Limited | Extraterritorial | 2003 |
| ST Cyrils Lettings Ltd | Real estate | 2024 |
| ST John Vascular LLP | | 2026 |
| ST. George Lodge RTM Company Ltd | Households | 2025 |
| ST. Range Properties Limited | Construction | 2003 |
| ST4 Group Ltd | Financial services | 2023 |
| Stade 2008 Limited | Extraterritorial | 2008 |
| Stamco Management Ltd | Financial services | 2022 |
| Stanbridge Lakes Management Company Limited | Administrative & support | 2013 |
| Standclear (Medical Education) Ltd | Education | 2022 |
| Stanley Butcher and Sons Limited | Wholesale & retail | 1975 |
| Starr Financial Holdings Limited | Financial services | 2023 |
| Start Your Own Business Limited | Information & communication | 2005 |
| State of Bass Ltd | Manufacturing | 2021 |
| Statement Graphics Limited | Manufacturing | 2018 |
| Stealth Carbon Ltd. | Professional & scientific | 2022 |
| Steam E Holdings Limited | Other services | 2014 |
| Steamy Windows (Southampton) Limited | Construction | 2005 |
| Steelcloud Limited | Information & communication | 2009 |
| Step Sourcing Ltd | Wholesale & retail | 2012 |
| Stephen Drinkwater Construction Limited | Construction | 2012 |
| Steve Willis Consultancy Limited | Other services | 2020 |
| Steveleesplanning Limited | Professional & scientific | 2016 |
| Steven Rowley Limited | Health & social care | 2007 |
| Stickley Enterprises Limited | Professional & scientific | 2024 |
| Stirrett-Hughes Ltd | Financial services | 2021 |