| Scoach Ltd | Other services | 2021 |
| Scorpion Brickwork Ltd | Construction | 2019 |
| SDL Executive Cars Limited | Transport & logistics | 2023 |
| Sea Salt Studio CIC | Health & social care | 2023 |
| Seafront Property Ltd | Real estate | 2024 |
| Seaview Estates Limited | Real estate | 1993 |
| Seaworth Galleries Ltd | Wholesale & retail | 2024 |
| Secure Drop Ltd | Construction | 2017 |
| Secure Glass and Glazing Ltd | Construction | 2008 |
| Sedco Properties Ltd | Real estate | 2018 |
| SEE Green CIC | Professional & scientific | 2023 |
| Seeded Retail Ltd. | Wholesale & retail | 2014 |
| Seedeehul Housing Project 1 Limited | Real estate | 2025 |
| Seisurv Ltd | Professional & scientific | 2012 |
| Sekr Ltd | Administrative & support | 2026 |
| Selbourne Mews Management Company Limited | Households | 2013 |
| Selkie Survey Ltd | Other services | 2022 |
| Selly Meats Limited | Wholesale & retail | 2023 |
| Sentimill Properties Ltd | Real estate | 2026 |
| Serafina Legal Services Limited | Other services | 2020 |
| Serendib Pride Ltd | Hospitality | 2026 |
| Serene Property Ltd | Construction | 2017 |
| Serenity Lifting Ltd | Construction | 2025 |
| Sergio G. Calvaresi Engineering Limited | Professional & scientific | 2018 |
| SET Surge Ltd | Professional & scientific | 2025 |
| Seven Potions Ltd | Wholesale & retail | 2024 |
| SF IT Services Ltd | Other services | 2009 |
| SF7 Limited | Professional & scientific | 2026 |
| SGL Southsea (Holdings) Limited | Hospitality | 2010 |
| Shaftesbury Mews Freehold Limited | Households | 2018 |
| Shaftesbury Road Residents Association Limited | Households | 1999 |
| Shah Taxi Services Ltd | Transport & logistics | 2025 |
| Shakti Care Services Ltd | Health & social care | 2007 |
| Shamobal Ltd | Wholesale & retail | 2025 |
| Shard Building Services Ltd | Construction | 2018 |
| Shaw Property Services Ltd | Construction | 2025 |
| SHC Renewable Energy Solutions Ltd | Construction | 2023 |
| SHE WHO Closes Ltd | Professional & scientific | 2026 |
| She's Sassy Media Ltd | Professional & scientific | 2021 |
| Sherepunjab Properties Limited | Real estate | 2002 |
| Sherlocks Bar (Southsea) Ltd | Hospitality | 2020 |
| Shining Food Garden Limited | Hospitality | 2025 |
| Shock N AWE Ltd | Administrative & support | 2012 |
| Shopov Building Ltd | Construction | 2023 |
| Show Pride CIC | Professional & scientific | 2024 |
| Shroomsday Ltd | Wholesale & retail | 2024 |
| Shundor Limited | Hospitality | 2019 |
| Siga Solutions Limited | Information & communication | 2014 |
| Signal Analytics Ltd | Professional & scientific | 2018 |
| Signetix Ltd | Information & communication | 2020 |
| Silk Mart Limited | Wholesale & retail | 2025 |
| Sillsport Management Limited | Arts & recreation | 2006 |
| Silver & Grey Limited | Information & communication | 2016 |
| Silvernet Properties Ltd | Real estate | 2016 |
| Silverthorne 1965 Ltd | Other services | 2020 |
| Silverwood Supplies Ltd | Wholesale & retail | 2026 |
| Simmons Hospitality Limited | Hospitality | 2020 |
| Simon Benfield Consulting Limited | Professional & scientific | 2025 |
| Simon Property Investments Ltd | Real estate | 2024 |
| Sipan Barber Ltd | Other services | 2023 |
| Sipho-Ntlantla Limited | Health & social care | 2011 |
| Sisters of Chaos Limited | Other services | 2019 |
| Sixstorey Digital Limited | Information & communication | 2026 |
| Sixstorey Limited | Real estate | 2017 |
| SJ Health Plus Limited | Health & social care | 2025 |
| SJR Solars Limited | Energy | 2025 |
| SJS Assets Ltd | Real estate | 2023 |
| SK Southern Building Services Ltd | Construction | 2025 |
| Skin Remedy Ltd | Health & social care | 2020 |
| SKJ Financial Consulting Limited | Financial services | 2018 |
| Sksb Limited | Professional & scientific | 2011 |
| Sky Lite Production Limited | Construction | 2022 |
| Skyline Build Marketing Limited | Professional & scientific | 2026 |
| Skyrock Services Ltd | Transport & logistics | 2019 |
| SL Composites Ltd | Professional & scientific | 2025 |
| Slicecraft Limited | Manufacturing | 2025 |
| SLR Recruitment Solutions Limited | Administrative & support | 2017 |
| Smardi Ltd | Wholesale & retail | 2020 |
| Smart Touch (UK) Limited | Wholesale & retail | 2004 |
| Smart-Buy Retail Ltd | Wholesale & retail | 2015 |
| Smartcell Warehouse Ltd | Wholesale & retail | 2016 |
| Smashz Limited | Hospitality | 2026 |
| SMC Electrical Solutions Limited | Construction | 2014 |
| SMS Marine Ltd | Professional & scientific | 2014 |
| Snapshot Audio Limited | Administrative & support | 2026 |
| SNG AI Limited | Information & communication | 2026 |
| SNG Wholesale Ltd | Wholesale & retail | 2026 |
| Social Enterprise Link (Wessex) CIC | Professional & scientific | 2011 |
| Softted Ltd | Information & communication | 2025 |
| Softworth Ltd | Information & communication | 2026 |
| SOHAIL.LOGISTICS1 Ltd | Transport & logistics | 2026 |
| Sohaila Sophia Coaching Ltd | Administrative & support | 2024 |
| SOL Rentals Limited | Administrative & support | 2025 |
| Solar Maintenance and Repairs Ltd | Manufacturing | 2025 |
| Solarco Energy Ltd | Construction | 2026 |
| Sole Partners Ltd | Administrative & support | 2013 |
| Soleful Ltd | Health & social care | 2018 |
| Solent Apartments RTM Company Limited | Households | 2024 |
| Solent Construction Services Ltd | Administrative & support | 2016 |
| Solent Court Management Company (Portsmouth) Limited | Hospitality | 1982 |