| SD Airconditioning Services Ltd | Energy | 2022 |
| SD Beauty & Hair Ltd | Other services | 2019 |
| SD Handyman Services Ltd | Construction | 2023 |
| SDD Medical Group Ltd | Wholesale & retail | 2018 |
| SDL FM Services Ltd | Administrative & support | 2021 |
| Sdlc Compliance Ltd | Professional & scientific | 2019 |
| Sdlonyer Management Limited | Extraterritorial | 2024 |
| SDR Services Ltd | Professional & scientific | 2007 |
| Sdukproducts Ltd | Wholesale & retail | 2024 |
| SDX Consulting Ltd | Professional & scientific | 2025 |
| SE Bakery Ltd | Hospitality | 2026 |
| SE1 Dessert House Limited | Wholesale & retail | 2026 |
| SE20 DRY Cleaners Ltd | Other services | 2018 |
| SE6 Desserts Limited | Wholesale & retail | 2024 |
| Sea 33 Limited | Hospitality | 2019 |
| Sea Breaze Limited | Hospitality | 2018 |
| Sea Lane Cafe Limited | Hospitality | 2004 |
| Sea Medicos Ltd | Health & social care | 2021 |
| Sea Moss Plus Ltd | Wholesale & retail | 2025 |
| Sea Recruitment Limited | Administrative & support | 2019 |
| Sea Spray Brighton Limited | Hospitality | 2020 |
| Sea Tower Apartments Limited | Households | 2007 |
| Seacom Technologies Co., Ltd | Manufacturing | 2025 |
| Seafisk Limited | Extraterritorial | 2010 |
| Seahorse (Ace) Ltd | Health & social care | 2016 |
| Seahorse (Princes Way) Limited | Health & social care | 2019 |
| Seahorse (S. London) Limited | Administrative & support | 2026 |
| Seahorse (Wimbledon) Limited | Administrative & support | 2017 |
| Seal Laundry Management Company Limited | Real estate | 2013 |
| Seal Solutions Limited | Construction | 2026 |
| Sean Black Ltd | Construction | 2024 |
| Sean Doyle Scaffolding Ltd | Construction | 2001 |
| Sean Doyle Group UK Limited | Financial services | 2020 |
| Search Solvers Limited | Information & communication | 2025 |
| Searched Limited | Professional & scientific | 2013 |
| Searle & Company,Limited | Wholesale & retail | 1909 |
| Searle Grove Management Company Limited | Households | 2022 |
| Searlewood Court Management Limited | Households | 2001 |
| SEB Travel and Tour Limited | Administrative & support | 2016 |
| Sebgeorge Construction Limited | Construction | 2023 |
| SEC Norbury Limited | Construction | 1997 |
| Second 2 None Automotive Ltd | Wholesale & retail | 2021 |
| Second Bagleys Lane Management Company Limited | Households | 1982 |
| Second Degree Consulting Limited | Financial services | 2022 |
| Second Degree Ltd | Arts & recreation | 2012 |
| Second Handed Ltd | Wholesale & retail | 2024 |
| Secret Events London Ltd | Administrative & support | 2018 |
| Sectorlumen Ltd | Information & communication | 2026 |
| Sectorspan Community Interest Company | Professional & scientific | 2025 |
| Secure Cover Services Limited | Information & communication | 2025 |
| Secure Cyber Solutions Limited | Information & communication | 2016 |
| Secure Motor Ltd | Wholesale & retail | 2018 |
| Secure Reversions Limited | Real estate | 2006 |
| Secure Security Solutions Ltd | Other services | 2018 |
| Secure Stays Ltd | Real estate | 2025 |
| Secureapp Technologies Limited | Information & communication | 2025 |
| Securekey 24H Ltd | Administrative & support | 2025 |
| Sedbury Pharma Ltd | Wholesale & retail | 2025 |
| Sedgeshire Limited | Construction | 1973 |
| Sedna's Beauty Ltd | Wholesale & retail | 2025 |
| Seebt Ltd | Extraterritorial | 2023 |
| Seed to Sky Ventures Limited | Financial services | 2025 |
| Seedbed Consulting Ltd | Education | 2013 |
| Seedling Startups Ltd | Professional & scientific | 2023 |
| Seedlings Equine Limited | Agriculture & fishing | 2022 |
| Seema Beauty Ltd | Wholesale & retail | 2025 |
| Seena & Varun Ltd | Real estate | 2020 |
| Sefton Group Holdings Limited | Financial services | 2022 |
| Sehion Consulting Ltd | Information & communication | 2023 |
| Sehnsa Ltd | Financial services | 2022 |
| Sekar Electrical Services Ltd | Construction | 2020 |
| Selborne Properties Limited | Real estate | 1959 |
| Selby Lodge (Cheltenham) Management Company Limited | Households | 2001 |
| Select Exec Transport Ltd | Transport & logistics | 2018 |
| Selectfurniture Ltd | Other services | 2026 |
| Self Assessment Accounting Services Limited | Professional & scientific | 2014 |
| Self Titled Ltd | Wholesale & retail | 2026 |
| Selhurst Property Management Ltd | Real estate | 2021 |
| Sellevoll Holdings Ltd | Financial services | 2025 |
| Sellovia Limited | Wholesale & retail | 2025 |
| Selsdon Road Kebab Ltd | Hospitality | 2022 |
| Selsun Valencia Limited | Real estate | 1990 |
| Semaj Management Limited | Professional & scientific | 2021 |
| Semeadores DE Maratane Ltd | Health & social care | 2020 |
| SEN VN 2 Ltd | Hospitality | 2024 |
| Senary Services Limited | Information & communication | 2023 |
| Senator Houghton Regis Limited | Households | 1988 |
| Senator Roofing and Building Ltd | Construction | 2021 |
| Sencl Ltd | Administrative & support | 2025 |
| Send Assistant Ltd | Education | 2025 |
| Sendstar Ltd | Education | 2023 |
| Senfina FS Limited | Professional & scientific | 2022 |
| Senior Practitioners Care Limited | Health & social care | 2022 |
| Senkus Limited | Construction | 2014 |
| Senmai Ltd | Other services | 2026 |
| Senoj Jones Services Ltd | Real estate | 2021 |
| Sensometrica Limited | Professional & scientific | 2013 |
| Sensus 3 Limited | Information & communication | 2004 |
| Sentinel Safety Services Ltd | Professional & scientific | 2026 |
| Senzmate UK Ltd | Information & communication | 2021 |