| Seadon Engineering Ltd | Professional & scientific | 2011 |
| Seafood Companies Ltd | Wholesale & retail | 2024 |
| Seagrave French LLP | | 2011 |
| Seahorse Rentals Ltd | Real estate | 2025 |
| Seal Calibration Limited | Professional & scientific | 2014 |
| Seal Medical Supplies Ltd | Wholesale & retail | 2008 |
| Seal Service Holdings Limited | Financial services | 2018 |
| Sealand Developments Ltd. | Administrative & support | 2015 |
| Sealed and Secure Ltd | Construction | 2019 |
| Sealed Forever Limited | Health & social care | 2023 |
| Seals Locker Ltd | Wholesale & retail | 2021 |
| Sealtight Gaskets Limited | Manufacturing | 1993 |
| Sean Baker Transport Limited | Transport & logistics | 2015 |
| Sean Clarke Bricklayer Ltd | Construction | 2019 |
| Sean Hickey Groundworks Limited | Construction | 2019 |
| Sean Mccafferty Building and Landscape Services Ltd | Construction | 2003 |
| Sean Paul Cleaning Nottingham Limited | Administrative & support | 2022 |
| Seannyeto Social Care Limited | Health & social care | 2013 |
| Search Party Productions Ltd | Information & communication | 2009 |
| Seascale Stores Ltd | Wholesale & retail | 2019 |
| Seashore Circle LLP | | 2017 |
| Seasons Springside Management Limited | Households | 2012 |
| Seasons Thurnscoe Management Company Limited | Households | 2011 |
| Seaton House Management Co Limited | Real estate | 2006 |
| Seaton Ross Ltd | Manufacturing | 2021 |
| Seatravel Limited | Administrative & support | 2025 |
| Seava Ltd | Wholesale & retail | 2025 |
| Seaview House Management Company Limited | Extraterritorial | 2001 |
| SEB Planning and Development Ltd | Professional & scientific | 2023 |
| Sebb Property Ltd | Construction | 2025 |
| Sebring Tree Care Ltd | Administrative & support | 2025 |
| Sebs Plumbing and Heating Limited | Construction | 2021 |
| Sec-Eco Group Ltd | Construction | 2025 |
| Secas Security Limited | Administrative & support | 2021 |
| Seccombe Building and Maintenance Limited | Construction | 2018 |
| Seccombe Property Group Limited | Real estate | 2018 |
| Seckou Music Ltd | Information & communication | 2021 |
| Seco Systems Limited | Information & communication | 2004 |
| Second Chance Distributors Limited | Wholesale & retail | 2024 |
| Second Chance Learning Academy | Education | 2015 |
| Second City Consulting Limited | Professional & scientific | 2025 |
| Second Golden AGE Limited | Education | 2023 |
| Second Hand Threads Limited | Wholesale & retail | 2025 |
| Second Look Aesthetics Ltd | Health & social care | 2018 |
| Second Look Medical Group Ltd | Health & social care | 2021 |
| Second Take Sports Limited | Manufacturing | 2020 |
| Second Thunder Limited | Professional & scientific | 2005 |
| Secret Builder Limited | Professional & scientific | 2022 |
| Secret Property Company Limited | Real estate | 2020 |
| Secret Recordings Ltd | Information & communication | 2019 |
| Secret Squirrel Hosts Ltd | Hospitality | 2024 |
| Secret Sugar Club Limited | Other services | 2023 |
| Secret Vault Limited | Hospitality | 2024 |
| Secsy Limited | Professional & scientific | 2002 |
| Sector Learning Limited | Professional & scientific | 2019 |
| Secure a Home Limited | Construction | 2019 |
| Secure Accommodation Limited | Real estate | 2001 |
| Secure Anchor Healthcare Limited | Health & social care | 2023 |
| Secure Bidco Limited | Financial services | 2021 |
| Secure Destruction Limited | Water & waste | 2008 |
| Secure Disk Technologies (UK) Ltd | Wholesale & retail | 2010 |
| Secure Glaze UK Home Improvements Ltd | Construction | 2018 |
| Secure Immigration Services Ltd | Professional & scientific | 2025 |
| Secure Sounds and Vision Limited | Wholesale & retail | 2004 |
| Secure Topco Limited | Financial services | 2021 |
| Secure Your Place Ltd | Real estate | 2025 |
| Secured Mortgages Limited | Financial services | 2017 |
| Security Aware Ltd | Information & communication | 2010 |
| Security Consultancy Specialists Ltd | Administrative & support | 2023 |
| Securityandstewardsuk Limited | Administrative & support | 2016 |
| SECURK9 Limited | Administrative & support | 2025 |
| Sedef Personal Training Ltd | Arts & recreation | 2021 |
| Sedeqi Limited | Construction | 2022 |
| SEE Consulting Services Limited | Health & social care | 2015 |
| SEE Group Limited | Arts & recreation | 2007 |
| SEE Patterns Limited | Information & communication | 2016 |
| SEE Speak Hear Limited | Professional & scientific | 2016 |
| Seed Cycle Limited | Manufacturing | 2024 |
| Seedar Finance Limited | Financial services | 2024 |
| Seeds Foundation | Education | 2012 |
| Seek Appliances Ltd. | Wholesale & retail | 2024 |
| Seek Care Limited | Public administration | 2026 |
| Seek Innovation Consulting Ltd | Information & communication | 2024 |
| Seerfel Limited | Construction | 2002 |
| Seerfel Services Limited | Extraterritorial | 2006 |
| Seery Homes Ltd | Real estate | 2015 |
| Seery's Landscapes Limited | Administrative & support | 2007 |
| Seevar Convenience Ltd | Wholesale & retail | 2026 |
| Seeview Blinds Limited | Wholesale & retail | 2001 |
| Sefe Place C.I.C | Health & social care | 2009 |
| Seferi Trading Limited | Hospitality | 2024 |
| Sefton Park DC Ltd | Real estate | 2025 |
| Segensworth Business Centre (Management) Limited | Real estate | 2006 |
| SEH Accountancy Services Limited | Professional & scientific | 2013 |
| SEH Enterprise Partners Ltd | Professional & scientific | 2025 |
| Sehria Ltd | Health & social care | 2024 |
| Seiken Energy Ltd | Energy | 2026 |
| Seine Studios Ltd | Arts & recreation | 2025 |
| Seiun Solutions Limited | Information & communication | 2016 |
| SEK Developments Limited | Construction | 2018 |