| Secum Homes Limited | Real estate | 2021 |
| Secure a Site Limited | Administrative & support | 2024 |
| Secure Courier Post Ltd | Transport & logistics | 2019 |
| Secure Hospital Transport Ltd Limited | Transport & logistics | 2023 |
| Secure OPS Security Services Ltd | Administrative & support | 2024 |
| Secure Start Consulting Ltd | Information & communication | 2025 |
| Secure&Safe Ltd | Administrative & support | 2019 |
| SECURE24 Services Ltd | Administrative & support | 2023 |
| Securenet Security Limited | Administrative & support | 2025 |
| Securetech IT Ltd | Other services | 2023 |
| Security Assist Ltd | Other services | 2025 |
| Security G Ltd | Transport & logistics | 2023 |
| Securus Alarms Ltd | Administrative & support | 2015 |
| Sedete Ltd | Professional & scientific | 2022 |
| Sedland Ltd | Professional & scientific | 2026 |
| SEE Rentals Ltd | Real estate | 2025 |
| Seebeyond Solutions Limited | Information & communication | 2011 |
| Seed Bidco Limited | Health & social care | 2013 |
| Seed Newco Limited | Health & social care | 2013 |
| Seee Services Limited | Administrative & support | 2015 |
| Seehra Orthodontics Ltd | Health & social care | 2013 |
| Seerat Consultancy Limited | Information & communication | 2017 |
| Sees Roofing Ltd | Construction | 2024 |
| Seflo Ltd | Construction | 2014 |
| Sehaj Express Ltd | Transport & logistics | 2026 |
| Sehaj Logistics Ltd | Transport & logistics | 2025 |
| Sehaj Properties Ltd | Real estate | 2022 |
| Sehar Xpress Ltd | Administrative & support | 2022 |
| Sehath Consulting Ltd | Public administration | 2024 |
| Sehra Property Ltd | Real estate | 2025 |
| Sekur Ltd | Wholesale & retail | 2022 |
| Seldom Investments Ltd | Real estate | 2023 |
| Select Car Traders Ltd | Wholesale & retail | 2024 |
| Selectsy Ltd | Wholesale & retail | 2025 |
| Selekt Langley Ltd | Hospitality | 2024 |
| Selekt Motors Ltd | Wholesale & retail | 2023 |
| Self Powered Safety Products Limited | Manufacturing | 2005 |
| Self Smart Ltd | Wholesale & retail | 2025 |
| Selfany Solutions Ltd | Wholesale & retail | 2025 |
| Selig UK Limited | Manufacturing | 2008 |
| Selimi Car Wash Ltd | Administrative & support | 2025 |
| Selimi Valeting Ltd | Administrative & support | 2025 |
| Sell Swift Limited | Wholesale & retail | 2024 |
| Sellrex Trading Limited | Wholesale & retail | 2020 |
| Sellshift Limited | Wholesale & retail | 2025 |
| Sellviix Limited | Wholesale & retail | 2026 |
| Selmakay Ltd | Health & social care | 2018 |
| Seltech Investment Ltd | Real estate | 2015 |
| Seltech Solutions Ltd | Wholesale & retail | 2014 |
| Sembhi Loans Limited | Financial services | 2018 |
| Semina Libertas Ltd | Hospitality | 2021 |
| Seminarium CIC | Education | 2026 |
| Send Success With Katie Ltd | Education | 2023 |
| Senice Properties Ltd | Real estate | 2025 |
| Senior Dental Ltd | Health & social care | 2024 |
| Sensational Quality Products Ltd | Wholesale & retail | 2021 |
| Senseit Limited | Information & communication | 2025 |
| Senta Saas Limited | Information & communication | 2014 |
| Sentinel K9 Security Services Ltd | Administrative & support | 2023 |
| Senturion International Limited | Administrative & support | 2012 |
| Seoni Limited | Wholesale & retail | 1999 |
| Sequence Property Management Ltd | Households | 2021 |
| Sequence Training (UK) Ltd | Administrative & support | 2012 |
| Sequins and Petals Limited | Administrative & support | 2014 |
| Sequoia Joinery & Carpentry Limited | Construction | 2023 |
| Serani Limited | Health & social care | 2025 |
| Serela Ltd | Wholesale & retail | 2025 |
| Serendipity & Co. Consultancy Ltd | Hospitality | 2024 |
| Serene IT Services Limited | Information & communication | 2026 |
| Serene Jewellery Ltd | Wholesale & retail | 2025 |
| Serene Mortgages Limited | Financial services | 2021 |
| Serenita Care Limited | Health & social care | 2020 |
| Serenity SELECTION1 UK Ltd | Wholesale & retail | 2024 |
| SERENITY7 Limited | Real estate | 2016 |
| Serghei R Ltd | Manufacturing | 2023 |
| Serra DA Estrela Ltd | Hospitality | 2015 |
| Serveforce Ltd | Real estate | 2005 |
| Service K&K Ltd | Transport & logistics | 2020 |
| Serviced Stays Limited | Hospitality | 2017 |
| Servier IP UK Limited | Administrative & support | 2006 |
| Servier Laboratories Limited | Wholesale & retail | 1963 |
| Servier Research and Development Limited | Professional & scientific | 1979 |
| Servis Heat Treatment Co.Limited | Manufacturing | 1958 |
| Servitor Sports UK Ltd | Manufacturing | 2023 |
| Servol Limited | Construction | 1992 |
| SES Bifold Ltd | Construction | 2019 |
| SES Installation Limited | Construction | 2026 |
| SES Investments Ltd | Real estate | 2018 |
| Setbeam Lighting Ltd | Manufacturing | 2026 |
| Seth's Recruitment Consultancy Ltd | Professional & scientific | 2024 |
| Sethi Enterprise Limited | Extraterritorial | 2020 |
| Sethi Estates Limited | Real estate | 2026 |
| Setla Ltd | Wholesale & retail | 2021 |
| Seunak Limited | Construction | 2019 |
| Seven Hexagons Ltd | Education | 2016 |
| Seven Ntek Ltd | Information & communication | 2024 |
| Sevenclicks Digital Solutions Ltd | Information & communication | 2022 |
| Sewor Ltd. | Health & social care | 2019 |
| SEX Brand Ltd | Wholesale & retail | 2020 |
| Sfar Technologies Ltd | Information & communication | 2026 |