| Speedy Pizza Limited | Extraterritorial | 1986 |
| Speedyfix Solutions Ltd | Information & communication | 2017 |
| Spektrum Events and Marketing Solutions Limited | Extraterritorial | 2009 |
| Speltham Dental Care Ltd | Health & social care | 2026 |
| Spelzini Splicing Solutions Ltd | Information & communication | 2023 |
| Spencer Close Developments Ltd | Real estate | 2020 |
| Spencer Stuart Limited | Financial services | 2015 |
| Spice House Portsmouth Limited | Real estate | 2010 |
| Spice Island Consultants Ltd | Professional & scientific | 2023 |
| Spice Island House Freehold Limited | Households | 2025 |
| SPICELOVERS139 Limited | Hospitality | 2025 |
| Spiffy Clean Limited | Administrative & support | 2024 |
| Spindlewood Place Management Company Limited | Real estate | 2024 |
| Spineart (UK) Ltd | Health & social care | 2012 |
| Spinnaker Construction & Maintenance Ltd | Construction | 2016 |
| Spinnaker Court Portsmouth (Management Company) Limited | Households | 2008 |
| Spinnaker Electrical and Mechanical Limited | Construction | 2024 |
| Spinnaker Electrical Group Limited | Financial services | 2024 |
| Spinnaker Inns Limited | Hospitality | 2019 |
| Spinnaker Lighting Limited | Construction | 2025 |
| Spinnaker Property Investments Limited | Real estate | 2020 |
| Spinnaker Restaurant Ltd | Hospitality | 2024 |
| Spiral Carpentry Limited | Construction | 2018 |
| Spiralworks Ltd | Construction | 2023 |
| Spitbank Property Limited | Real estate | 2016 |
| Spithead Trading Limited | Wholesale & retail | 1997 |
| Spiwell Mechanical Services Ltd | Construction | 2023 |
| SPJ Consultancy Limited | Professional & scientific | 2026 |
| Spmc Associates Ltd | Professional & scientific | 2012 |
| SPN Alliance Limited | Administrative & support | 2013 |
| SPN Holdings Ltd | Manufacturing | 2020 |
| Spoke College Green Limited | Wholesale & retail | 2023 |
| Spoon Portsmouth Ltd | Hospitality | 2016 |
| Sport 4 Primary | Education | 2018 |
| Sportsmans Mews Management Company Limited | Hospitality | 2013 |
| SPOTLESS911CLEANERS Limited | Administrative & support | 2025 |
| Spotswood Express Trans Ltd | Transport & logistics | 2024 |
| Spraywall Facade Systems Limited | Construction | 2026 |
| Spraywall Interiors Limited | Construction | 2021 |
| Springboard BID Writing Ltd | Professional & scientific | 2025 |
| Springboard BID Writing Services Ltd | Professional & scientific | 2024 |
| Springboard Speech and Language Ltd | Education | 2015 |
| Springfield Gardens (Romsey) Limited | Households | 2024 |
| Springvale Investments Limited | Other services | 2000 |
| Sprintera Ltd | Wholesale & retail | 2026 |
| SPW Interiors Ltd | Construction | 2023 |
| SQ & YL Limited | Hospitality | 2017 |
| Square Dining Limited | Hospitality | 2025 |
| Square GAS Limited | Construction | 2023 |
| Square Lemon Records Ltd | Information & communication | 2026 |
| Square Pound Ltd | Administrative & support | 2011 |
| Square Tower Ceremonies Limited | Real estate | 2010 |
| Square Tower Enterprises Ltd | Manufacturing | 2009 |
| Squibb Quantity Surveying Limited | Professional & scientific | 2023 |
| SRG Real Estate Limited | Real estate | 2025 |
| SRG Recruitment Ltd | Administrative & support | 2017 |
| SRI Dental Limited | Health & social care | 2024 |
| SRJ Events Limited | Hospitality | 2022 |
| SRL Investments Limited | Construction | 2001 |
| SRS Property Maintenance Ltd | Construction | 2026 |
| Srsp HR Technology Limited | Information & communication | 2023 |
| SS Construction Southern Ltd | Construction | 2014 |
| SSA Properties (Portsmouth) Ltd | Hospitality | 2012 |
| SSD Events and Marketing Limited | Arts & recreation | 2018 |
| SSD Music Ltd | Arts & recreation | 2015 |
| SSH Building Services Ltd | Construction | 2016 |
| SSH Cleaning Limited | Administrative & support | 1997 |
| SSH Flooring Ltd | Construction | 2016 |
| SSN Accountancy Ltd | Professional & scientific | 2024 |
| SSP Property RTM Company Ltd | Administrative & support | 2016 |
| SSR Management Limited | Wholesale & retail | 2012 |
| SSS Direct Limited | Professional & scientific | 2016 |
| ST Building Projects Ltd | Construction | 2026 |
| ST Cross Homes (Winchester) Limited | Construction | 2018 |
| ST Francis Practice Limited | Health & social care | 2002 |
| ST James Place Residents Management Company Limited | Households | 2013 |
| ST Josephs Court Southsea Management Limited | Real estate | 2012 |
| ST Martin's House (Southsea) Management Limited | Hospitality | 1964 |
| ST Templemead Ltd | Professional & scientific | 2022 |
| ST Thomas Court Fair Oak Ltd | Extraterritorial | 1983 |
| ST Thomas Court Freehold Ltd | Households | 2007 |
| ST. Catherine's Court (Hayling) Limited | Households | 2000 |
| ST. Cross Associates Limited | Professional & scientific | 2010 |
| ST. George Construction Limited | Construction | 2003 |
| ST. Helens Court Limited | Households | 1992 |
| St.Mary's Technologies Ltd | Health & social care | 2012 |
| ST9T5 Holdings Ltd | Financial services | 2021 |
| Stacey Court Residents Association Limited | Hospitality | 2003 |
| Stadbury Holdings Limited | Financial services | 2026 |
| Staff at Work Ltd | Real estate | 2021 |
| Stafford Rhodes Training and Development Limited | Professional & scientific | 2002 |
| Stag Lane Development (IOW) Ltd | Construction | 2019 |
| Stage 2 Service & Supply Limited | Other services | 2013 |
| Stagespark Ltd | Administrative & support | 2025 |
| Stain Free Ltd | Other services | 2024 |
| Stampy Limited | Information & communication | 2014 |
| Stamshaw Property Ltd | Real estate | 2025 |
| Stamshaw Takeaway Limited | Hospitality | 2016 |
| Standeven-Holden Property Maintenance Limited | Households | 2014 |
| Stanley's Butchers Limited | Wholesale & retail | 2011 |