| Search Elements Limited | Administrative & support | 2014 |
| Searchbi Contracts Limited | Professional & scientific | 2019 |
| Searchdata Group Limited | Other services | 2014 |
| Seascape Analytics Limited | Professional & scientific | 2013 |
| Seascape Holidays Limited | Other services | 2012 |
| Seashellsprig Ltd | Wholesale & retail | 2025 |
| Seaside Fishmongers Ltd | Wholesale & retail | 2025 |
| Seaside Properties (Cold Hawaii) Limited | Real estate | 2025 |
| Season 7 Limited | Professional & scientific | 2018 |
| Seastorm Limited | Information & communication | 2019 |
| Seatac Designers Ltd | Information & communication | 2018 |
| Seaton Court Cardiff RTM Company Ltd | Real estate | 2019 |
| Seaview Bar Ltd | Hospitality | 2021 |
| Seaview Capital Limited | Real estate | 2020 |
| Seaview Property Maintenance Limited | Construction | 2019 |
| Seawall MOT Limited | Transport & logistics | 2009 |
| Seaways Management Company Limited | Households | 2018 |
| Seawise Catering Ltd | Hospitality | 2019 |
| Seb-Reg Grips Ltd | Arts & recreation | 2019 |
| Sebastian Huckson Consultancy Services Ltd | Professional & scientific | 2018 |
| Sebastien Europe Ltd | Wholesale & retail | 2019 |
| Sebastienwarman Limited | Transport & logistics | 2025 |
| Sebbydee Catering Ltd | Hospitality | 2018 |
| Sebold's Originals Ltd | Information & communication | 2024 |
| Sebwik Ltd | Transport & logistics | 2020 |
| Seby Logistic Ltd | Transport & logistics | 2018 |
| Secint AI Ltd | Manufacturing | 2014 |
| Secint Design Limited | Professional & scientific | 2020 |
| Second Chance Bargains Ltd | Wholesale & retail | 2023 |
| Second City Media Limited | Administrative & support | 2000 |
| Second Hand Trading Limited | Wholesale & retail | 2015 |
| Second Jobs Co Limited | Administrative & support | 2017 |
| Second Stream Ltd | Information & communication | 2019 |
| Secret Beauty LAB Ltd | Other services | 2025 |
| Secret Garden Cafe (Hull) Ltd | Hospitality | 2023 |
| Secret Garden China Ltd | Wholesale & retail | 2019 |
| Secret Recruitment Limited | Administrative & support | 2018 |
| Secret Veneers Limited | Wholesale & retail | 2016 |
| Secretly Obsessed Ltd | Information & communication | 2025 |
| Section 31 Studios Ltd | Wholesale & retail | 2023 |
| Sectorsquare Residents Management Limited | Households | 1987 |
| Sectorstart Residents Management Limited | Households | 1988 |
| Secunda Ltd | Wholesale & retail | 2019 |
| Secur Trading Ltd | Administrative & support | 2018 |
| Secura Windows Limited | Construction | 2011 |
| Securalec Ltd | Construction | 2014 |
| Secure and Design Windows Doors Ltd | Manufacturing | 2018 |
| Secure Hold Vehicle Services Ltd | Transport & logistics | 2026 |
| Secure Leads Ltd | Information & communication | 2023 |
| Secure Pace Ltd | Professional & scientific | 2018 |
| Secure PAY Solutions Ltd | Administrative & support | 2018 |
| Secure Right Security Ltd | Administrative & support | 2024 |
| Secure Select Limited | Extraterritorial | 2025 |
| Secure That BAG Limited | Wholesale & retail | 2024 |
| Secureaxis Systems Ltd | Administrative & support | 2026 |
| Secured Info Limited | Information & communication | 2018 |
| Secureshreduk Limited | Water & waste | 2020 |
| Securetek Ltd | Wholesale & retail | 2017 |
| Securico Guard Services Ltd | Administrative & support | 2025 |
| Securime Ltd | Administrative & support | 2018 |
| Securist Limited | Administrative & support | 2009 |
| Securitech Ltd | Information & communication | 2019 |
| Security Drones UK Limited | Administrative & support | 2018 |
| Security Guardian Services Limited | Administrative & support | 2025 |
| Security Inc PC | | 2019 |
| Security Site Services Limited | Extraterritorial | 2007 |
| Security Solution Intelligence Limited | Administrative & support | 2024 |
| SECURITY2 Ltd | Professional & scientific | 2013 |
| Securitychain Ltd | Information & communication | 2020 |
| Securitywyse Limited | Information & communication | 2024 |
| Sedaina Ltd | Wholesale & retail | 2019 |
| Sedas G3 Ltd | Real estate | 2023 |
| Sedas Shas Holdings Ltd | Real estate | 2024 |
| Sedas Zrur Ltd | Real estate | 2024 |
| Sedgwick's Catering Limited | Hospitality | 2018 |
| Sedna Capital LLP | | 2022 |
| Sedna Group Limited | Real estate | 2020 |
| Sedna Holdings Limited | Real estate | 2012 |
| Sedna Lighting Limited | Manufacturing | 2012 |
| Sedo Solutions Limited | Professional & scientific | 2023 |
| Seduced by Art Ltd | Arts & recreation | 2020 |
| Seductive Stitches Ltd | Wholesale & retail | 2025 |
| SEE CON Limited | Construction | 2016 |
| SEE Science Limited | Education | 2011 |
| SEE What WE CAN Make Ltd | Construction | 2020 |
| Seec Property Limited | Real estate | 2016 |
| Seed Mentors Entrepreneurs Limited | Professional & scientific | 2017 |
| Seed N SOW Ltd | Wholesale & retail | 2020 |
| Seedable Studio Ltd | Information & communication | 2024 |
| Seeheim Limited | Real estate | 2022 |
| Seema 74 Ltd | Hospitality | 2024 |
| Seenar Cloud Furniture Ltd | Manufacturing | 2022 |
| Seenda Creation Limited | Wholesale & retail | 2021 |
| Seeplim Innovations Limited | Wholesale & retail | 2025 |
| Seer IT Consulting Limited | Information & communication | 2007 |
| Seer Tech Limited | Information & communication | 2026 |
| Seeras Limited | Construction | 2022 |
| Seers OIL and GAS Trading Ltd | Wholesale & retail | 2016 |
| Seers Support Services Limited | Administrative & support | 2009 |
| Seethe Techs Limited | Extraterritorial | 2021 |