| Sean Lynch Carpentry Ltd | Construction | 2014 |
| Search Station Digital Limited | Administrative & support | 2019 |
| Searchlight Learning Limited | Education | 2025 |
| Seaside Care KY Limited | Health & social care | 2015 |
| Seat Consultancy & Training Services Limited | Education | 2021 |
| Seax Global Risk Ltd | Administrative & support | 2026 |
| Sebastian Events Ltd | Hospitality | 2024 |
| Second Nature Hotels Limited | Hospitality | 2017 |
| Second Sight Investigations Limited | Professional & scientific | 2021 |
| Second Sight Support Services Limited | Financial services | 2009 |
| Secret Trading Company Limited | Wholesale & retail | 2020 |
| Secure Equinox Limited | Information & communication | 2014 |
| Secure Haven Ltd | Other services | 2013 |
| Securebase Groundscrews Ltd | Construction | 2024 |
| Secureguard Solutions Ltd | Administrative & support | 2026 |
| Securevoid Limited | Wholesale & retail | 2010 |
| Securia Limited | Professional & scientific | 2012 |
| Securityscorecard UK Limited | Administrative & support | 2021 |
| Sedgwick Renewable Energy Limited | Administrative & support | 2013 |
| Sedgwick Solar 3 Limited | Financial services | 2020 |
| Sedgwick Solar 4 Limited | Financial services | 2022 |
| Sedgwick Solar 5 Limited | Financial services | 2023 |
| Sedgwick Trading Limited | Financial services | 2013 |
| Sedgwick Trading Portfolio 1 Limited | Administrative & support | 2022 |
| Sedgwick Trading Portfolio 2 Limited | Administrative & support | 2022 |
| Sedgwick Trading Portfolio 3 Limited | Financial services | 2019 |
| Sedgwick Wind 6 Limited | Administrative & support | 2019 |
| Sedgwick Wind 8 Limited | Administrative & support | 2020 |
| Sedgwick Wind 9 Limited | Administrative & support | 2021 |
| Sedgwick Wind Limited | Administrative & support | 2017 |
| SEE Learning Ltd | Information & communication | 2024 |
| Segue Computing Limited | Information & communication | 2001 |
| Seitan's Quarters Ltd | Manufacturing | 2026 |
| Sekai Talent Limited | Other services | 2022 |
| SEL Finserv Limited | Professional & scientific | 2025 |
| Seldom Seen Limited | Administrative & support | 2004 |
| Select Building Solutions Ltd | Construction | 2004 |
| Select Property Services (UK) Ltd | Construction | 2012 |
| Selection Group Limited | Manufacturing | 2024 |
| Selective Networks Ltd | Information & communication | 2010 |
| Self Build Finance Ltd | Financial services | 2024 |
| Self Knowledge Global Responsibility | Education | 2011 |
| Selkie Swim Co Limited | Wholesale & retail | 2014 |
| Sellars Bridge Management Company (Hardwicke) Limited | Extraterritorial | 2013 |
| Sellek Wealth Management Limited | Financial services | 2010 |
| Selling by CAM Ltd | Wholesale & retail | 2025 |
| SEM Edits Ltd | Information & communication | 2023 |
| Semibiko Limited | Households | 2018 |
| Semitronics Sales Ltd. | Professional & scientific | 2013 |
| Sendme Limited | Construction | 2020 |
| Seneca BI Ltd | Information & communication | 2019 |
| Senior Steel Limited | Construction | 1999 |
| Senna Product Services Limited | Administrative & support | 2006 |
| Sense Consultancy CIC | Education | 2025 |
| Senses Healing Limited | Other services | 2025 |
| Sensiotech Limited | Information & communication | 2013 |
| Sensitive Skin Company Ltd | Other services | 2025 |
| Sensor Tower UK Ltd | Information & communication | 2019 |
| Senstar Limited | Wholesale & retail | 1987 |
| Sent West Ltd | Information & communication | 2022 |
| Sentients Cybersecurity Limited | Administrative & support | 2021 |
| Sentinel Labs Ltd | Information & communication | 2016 |
| Sentinel Legal Limited | Professional & scientific | 2020 |
| Sentrivault Cyber Consulting Limited | Information & communication | 2025 |
| Sentry SL Ltd | Manufacturing | 2017 |
| Separation Techniques Ltd | Professional & scientific | 2013 |
| Separation Technologies Investments Limited | Professional & scientific | 2013 |
| Separation Technologies Limited | Professional & scientific | 1994 |
| Sephora Clinic Ltd | Other services | 2022 |
| Sequester Holdings Ltd | Financial services | 2023 |
| Sequester Limited | Real estate | 2022 |
| Serac Consulting Limited | Information & communication | 2011 |
| Seraphina Aesthetic Clinic Ltd | Professional & scientific | 2017 |
| Seren Equestrian Ltd | Administrative & support | 2012 |
| Seren Limited | Administrative & support | 1986 |
| Serendipity Bespoke Woodcraft Ltd | Manufacturing | 2023 |
| Serendipity Shoes Limited | Wholesale & retail | 2015 |
| Serenity Caskets and Coffins UK Limited | Other services | 2025 |
| Serenity Hair and Beauty Limited | Other services | 2015 |
| Series B Limited | Administrative & support | 2015 |
| Serimot Limited | Households | 1985 |
| Serve.Clothing Ltd | Wholesale & retail | 2026 |
| Service Location Limited | Administrative & support | 2007 |
| SET Creative Studio Ltd | Information & communication | 2018 |
| SET Square Architectural Services Ltd | Professional & scientific | 2023 |
| Seton-Chase Limited | Information & communication | 1998 |
| Sevargi Consulting Limited | Professional & scientific | 2018 |
| Seven Acres Close Management Company Limited | Households | 2019 |
| Seven Arches Management Limited | Households | 1999 |
| Seven Seeds Property Ltd | Real estate | 2018 |
| Seven Springs Investments Limited | Financial services | 2021 |
| Seventeen Estates Ltd | Real estate | 2024 |
| Seventwentyseven Ltd | Transport & logistics | 2018 |
| Seventynine Eco Limited | Construction | 2023 |
| Seventynine Group Limited | Professional & scientific | 2015 |
| Seventynine Holdings Limited | Financial services | 2021 |
| Severn Agriculture Ltd | Manufacturing | 2014 |
| Severn Glocon Group Limited | Manufacturing | 1987 |
| Severn Grange Properties Limited | Households | 1992 |
| Severn Hosting Limited | Information & communication | 2020 |