| SDU Transport Ltd | Transport & logistics | 2020 |
| SDW Process Engineering Limited | Administrative & support | 2025 |
| SE Home & Garden Improvements Limited | Administrative & support | 2019 |
| Se&I Limited | Administrative & support | 2026 |
| SE2A Limited | Information & communication | 2020 |
| Sea Change SEO Ltd | Other services | 2021 |
| Sea Kayaking U.K. Ltd. | Manufacturing | 2003 |
| SEA17 Limited | Information & communication | 2023 |
| SEA2SKY Limited | Professional & scientific | 2007 |
| Seaf Services Limited | Professional & scientific | 2018 |
| Seager Consulting Ltd | Information & communication | 2023 |
| Seahorse Accounting Limited | Professional & scientific | 2018 |
| Seal Resource Management Limited | Administrative & support | 2015 |
| Seal-Er Ltd | Manufacturing | 2019 |
| Sealeaf Properties Limited | Real estate | 2021 |
| Sean Donnelly Ltd | Professional & scientific | 2022 |
| Sean GEM Ltd | Hospitality | 2026 |
| Sean Nils Dunstan Ltd | Wholesale & retail | 2026 |
| Sean Preston Hair Ltd | Other services | 2018 |
| Sean Richards Construction Ltd | Construction | 2023 |
| Sean Roche Temporary Limited | | 2013 |
| Sean William Mckinstry Limited | Administrative & support | 2010 |
| Seapoint Wholesale Ltd | Wholesale & retail | 2025 |
| Searchworks Recruitment Limited | Administrative & support | 2014 |
| Seaview Media Ltd | Information & communication | 2016 |
| SEB Logistics Ltd | Transport & logistics | 2013 |
| SEB Petrillo Limited | Administrative & support | 2016 |
| Sebastian James Developments Ltd | Administrative & support | 2022 |
| Secateur Sisters Garden Design Ltd | Professional & scientific | 2012 |
| Second Chance 92 Ltd | Wholesale & retail | 2024 |
| Second Impact Games Limited | Information & communication | 2011 |
| Second Skin Ltd | Wholesale & retail | 2025 |
| Second Star Games Limited | Information & communication | 2025 |
| Section Limited | Professional & scientific | 2016 |
| Sectorlinkapp Ltd | Information & communication | 2021 |
| Secure Access Scaffolding Limited | Construction | 2009 |
| Secure Cyber Management Ltd | Information & communication | 2019 |
| Secure IA Limited | Information & communication | 2010 |
| Secure Implementation Services Ltd. | Information & communication | 2005 |
| Secure Pets Limited | Wholesale & retail | 2024 |
| Secure-At-Ease Limited | Administrative & support | 1995 |
| Secured Express Limited | Transport & logistics | 2011 |
| Secured Mail Limited | Transport & logistics | 2005 |
| Security Risk Management Consultants- Global Ltd | Administrative & support | 2016 |
| Security Syndicat London UK Ltd | Administrative & support | 2023 |
| Seddon Distribution Ltd | Wholesale & retail | 2022 |
| Seddon Holdings (North West) Limited | Financial services | 2026 |
| Seddon Homes (Alsager) Limited | Real estate | 2010 |
| Seddon Homes (Belmont) Limited | Real estate | 2010 |
| Seddon Homes (Congleton West) Limited | Real estate | 2012 |
| Seddon Homes (Congleton) Limited | Real estate | 2010 |
| Seddon Homes (Crewe) Limited | Real estate | 2011 |
| Seddon Homes (Disley) Limited | Real estate | 2009 |
| Seddon Homes (Gawsworth) Limited | Real estate | 2011 |
| Seddon Homes (Haslington) Limited | Real estate | 2012 |
| Seddon Homes (JP) Limited | Real estate | 2011 |
| Seddon Homes (Land) Limited | Real estate | 2011 |
| Seddon Homes (Langley) Limited | Real estate | 2009 |
| Seddon Homes (Lawton) Limited | Real estate | 2013 |
| Seddon Homes (Madeley) Limited | Real estate | 2009 |
| Seddon Homes (Nantwich) Limited | Real estate | 2010 |
| Seddon Homes (Property) Limited | Construction | 2009 |
| Seddon Homes (Stafford) Limited | Real estate | 2009 |
| Seddon Homes (Standish) Limited | Real estate | 2009 |
| Seddon Homes (Wrenbury) Limited | Real estate | 2011 |
| Seddon Homes Limited | Construction | 1995 |
| Seddon Shine Detailing Ltd | Administrative & support | 2022 |
| Seddon's Properties Ltd | Real estate | 2025 |
| Sedley Consulting Ltd | Professional & scientific | 2025 |
| SEE Sharp Services Ltd | Transport & logistics | 2021 |
| Seedwood Limited | Financial services | 2013 |
| SEEK4 Ltd | Information & communication | 2023 |
| Seen Worse Ltd | Administrative & support | 2026 |
| Sefg Advanced Technologies Limited | Energy | 2023 |
| Sefg Biofuels Limited | Professional & scientific | 2022 |
| Sefg Energy Storage Limited | Construction | 2023 |
| Segfolt Inc. Ltd | Professional & scientific | 2025 |
| Segitech IT Solutions Limited | Information & communication | 2012 |
| Seine Consult Ltd | Administrative & support | 2007 |
| Seismologi.St Limited | Administrative & support | 2015 |
| Selcuk Investments Ltd | Financial services | 2023 |
| Selected Transport Ltd | Transport & logistics | 2019 |
| Selenta Limited | Arts & recreation | 2012 |
| Selenta Properties Ltd | Real estate | 2026 |
| Selfie Productions Limited | Information & communication | 2025 |
| Sellafield Limited | Other services | 1971 |
| Sellars Elite Coaching Limited | Arts & recreation | 2020 |
| Sellick Creative Co Ltd | Administrative & support | 2023 |
| Sellzona Trading Limited | Wholesale & retail | 2025 |
| Selva NVN Ltd | Wholesale & retail | 2023 |
| Selwell Limited | Wholesale & retail | 2021 |
| SEM Sporting Activities CIC | Arts & recreation | 2024 |
| SEM Sports Ltd | Arts & recreation | 2023 |
| Semaj Campbell Limited | Construction | 2018 |
| Semantic Fusion Limited | Information & communication | 2008 |
| Semaphore Cyber Solutions Limited | Information & communication | 2016 |
| Semper Advisory Limited | Professional & scientific | 2024 |
| Sempra Consultancy Ltd | Professional & scientific | 2023 |
| SEN4U Limited | Administrative & support | 2026 |
| Send Noods Limited | Hospitality | 2023 |