| Scoreline Ltd | Education | 2023 |
| Scott Bradley Ltd | Construction | 2025 |
| Scott Cables Limited | Manufacturing | 2012 |
| Scott Cantlow Fabrication Limited | Construction | 2015 |
| Scott Thatcher Limited | Arts & recreation | 2004 |
| Scotts Contract Services Ltd | Administrative & support | 2002 |
| Scotwear Limited | Wholesale & retail | 2024 |
| Scrapthatmetals Ltd | Water & waste | 2025 |
| Screamandshout Property Limited | Financial services | 2022 |
| Screams Ice Creams Ltd | Hospitality | 2018 |
| Screed DRY Ltd | Construction | 2024 |
| Screenprint 87 Ltd | Extraterritorial | 2014 |
| Scriptovate Ltd | Information & communication | 2026 |
| SCS Media & Merch Ltd | Wholesale & retail | 2026 |
| SCT Civil Engineering Ltd | Construction | 2014 |
| SCT Site Services Ltd | Construction | 2018 |
| SD Brickwork Ltd | Construction | 2022 |
| SD Club Ltd | Hospitality | 2024 |
| SD Consultancy (North) Limited | Hospitality | 2020 |
| SD Studios Portsmouth Ltd | Arts & recreation | 2018 |
| SD Trading Cards Ltd | Wholesale & retail | 2021 |
| SDG Plant Services Limited | Administrative & support | 2007 |
| SDH Consultancy Limited | Information & communication | 2012 |
| SDP Gastroenterology Limited | Health & social care | 2019 |
| SDS Developments Southern Ltd | Construction | 2022 |
| SDS Marine (Southern) Ltd | Manufacturing | 2019 |
| SE7EN Property Ltd | Construction | 2021 |
| Sea & Soul Ltd | Education | 2023 |
| Sea Blue Properties Limited | Real estate | 2019 |
| Sea Energy Limited | Wholesale & retail | 2024 |
| Sea Path Films Ltd | Administrative & support | 2025 |
| Sea Wave Portsmouth Limited | Hospitality | 2020 |
| Sea-Fire (Holdings) Limited | Professional & scientific | 2006 |
| Sea-Fire Europe Limited | Manufacturing | 2000 |
| Seabalt Technologies Limited | Information & communication | 2025 |
| Seabot Maritime Limited | Information & communication | 2017 |
| Seacorp Technologies Limited | Information & communication | 2015 |
| Seafront Furniture Ltd | Manufacturing | 2019 |
| Seaglass Limited | | 1967 |
| Sealaw Property Limited | Real estate | 2023 |
| Sean Codling Ltd | Financial services | 2025 |
| Searchlight Cyber Ltd | Information & communication | 2017 |
| Searchlight Management Services Limited | Administrative & support | 2001 |
| Searle’S Transport Ltd | Transport & logistics | 2018 |
| Seaside 43 Limited | Real estate | 2018 |
| Seaside Delights Limited | Hospitality | 2023 |
| Seaside Scaffolding Solutions Limited | Construction | 2026 |
| Seaways Global Ltd | Professional & scientific | 2011 |
| Seawolf Facilities Services Ltd | Construction | 2023 |
| SEB Air Conditioning Ltd | Energy | 2024 |
| SEC Gb&Ni Ltd | Construction | 2021 |
| Second Millennium Building Co Limited | Construction | 1998 |
| Secondcentre Limited | Real estate | 2018 |
| Secret Circus Productions Ltd | Arts & recreation | 2021 |
| Secret Circus Studio Ltd | Arts & recreation | 2015 |
| Secure Projects Limited | Construction | 2026 |
| Securonix UK Ltd | Administrative & support | 2012 |
| Seek to Protect Limited | Financial services | 2023 |
| Seekers Social Enterprize C.I.C. | Other services | 2014 |
| Segensworth Ltd | Professional & scientific | 2025 |
| SEH Drywall Ltd | Construction | 2022 |
| SEH Technology UK Limited | Information & communication | 2000 |
| Selcem Limited | Hospitality | 2020 |
| Selclene (Southampton) Ltd | Households | 2016 |
| Selecthomeshare Ltd | Real estate | 2014 |
| Self Actualise Ltd | Arts & recreation | 2023 |
| Selsey Womens FC CIC | Arts & recreation | 2022 |
| SEM Holdings Limited | Financial services | 2020 |
| Semper V Limited | Professional & scientific | 2022 |
| Sempiterne Ltd. | Wholesale & retail | 2024 |
| Semple.Agency Ltd | Professional & scientific | 2020 |
| Send IT Solar Ltd | Construction | 2021 |
| Senera Care Limited | Health & social care | 2024 |
| Sensational Bricks Ltd | Wholesale & retail | 2020 |
| Sentient Media Limited | Information & communication | 2026 |
| Sentinel 7 Office Supplies Ltd | Wholesale & retail | 2018 |
| Sentinel Portfolio Management Limited | Professional & scientific | 2019 |
| September House Holding Ltd | Financial services | 2021 |
| Sequence Digital Limited | Information & communication | 2018 |
| Seraco Limited | Real estate | 2015 |
| Serenity Counselling & Psychotherapy Ltd | Health & social care | 2016 |
| Serenity Digital Limited | Information & communication | 2012 |
| Seri PM Limited | Real estate | 2022 |
| Serocor Holdings Limited | Professional & scientific | 2007 |
| Serocor Investments Limited | Financial services | 2020 |
| SERV4 U Construct Ltd | Construction | 2020 |
| Service Champions Limited | Wholesale & retail | 2012 |
| Service Light Limited | Information & communication | 2023 |
| Sessebe Limited | Real estate | 2012 |
| SET E-Commerce Ltd | Wholesale & retail | 2016 |
| Setanta Developments Ltd | Manufacturing | 2014 |
| Sethi Family Office Ltd | Financial services | 2025 |
| Sethi Food and Beverages Limited | Wholesale & retail | 2025 |
| Sethopah Ltd | Health & social care | 2025 |
| Seven Days Care Limited | Health & social care | 2025 |
| Seven Hills Developments Limited | Construction | 2023 |
| SEW Finee Limited | Manufacturing | 2026 |
| Sewa Barbers T/A Bridge Barbers Limited | Other services | 2021 |
| Sextons Commercials Sound Ltd | Wholesale & retail | 2016 |
| Sexy Duck Limited | Hospitality | 2023 |