| SD Railtech Ltd | Manufacturing | 2026 |
| SD Wadsworth Limited | Construction | 2017 |
| SD22 Ltd | Construction | 2025 |
| Sdcl Consultants Ltd | Real estate | 2025 |
| SDG Supply Chain Consultancy Limited | Information & communication | 2019 |
| SDH23 Limited | Administrative & support | 2023 |
| SDJ Music Ltd | Wholesale & retail | 2023 |
| SDM Fitters Ltd | Manufacturing | 2024 |
| Sdpmc Ltd | Real estate | 2024 |
| SDR Solutions Ltd | Transport & logistics | 2026 |
| SE 100-109 Limited | Real estate | 2025 |
| SE Drinks Limited | Wholesale & retail | 2022 |
| SE Events Limited | Administrative & support | 2024 |
| Sea Shell Gaming Limited | Arts & recreation | 2023 |
| Sea Shell Holdings Limited | Professional & scientific | 2020 |
| Sea Smile Limited | Administrative & support | 2018 |
| Seaburne Limited | Construction | 2020 |
| Seagull (Derby) Fish Bar Limited | Hospitality | 2017 |
| Seal of Excellence Limited | Real estate | 2004 |
| Seals R US Ltd | Wholesale & retail | 2019 |
| Sealy Shaw Accountants Limited | Professional & scientific | 2006 |
| Sealy Shaw Bookkeeping Limited | Professional & scientific | 2024 |
| Sean O'Brien Limited | Manufacturing | 2017 |
| Sean Transports Ltd | Transport & logistics | 2025 |
| Sear Engineering Services Limited | Manufacturing | 1998 |
| Seathan Ltd | Health & social care | 2025 |
| Seaview Apartments Cornwall Ltd | Hospitality | 2018 |
| Seaview Bricklaying Ltd | Construction | 2016 |
| SEB Leheup-Jones Consultancy Ltd | Professional & scientific | 2023 |
| Seb-Pol Ltd | Transport & logistics | 2017 |
| Sebaa DON Limited | Wholesale & retail | 2025 |
| Sebara Ventures Ltd | Real estate | 2019 |
| Sebcorp Limited | Administrative & support | 2016 |
| Second Sitting Restaurants Limited | Hospitality | 2026 |
| Second Steps Day Nursery Limited | Education | 2011 |
| Secondchance Recruitment Ltd | Administrative & support | 2025 |
| Secretpower Ltd | Wholesale & retail | 2020 |
| Section 5 Airsoft Ltd | Arts & recreation | 2026 |
| Secura Hosting Ltd | Information & communication | 2001 |
| Secure Integration Engineering Ltd | Information & communication | 2016 |
| Secure Perimeter Ltd | Information & communication | 2024 |
| Secure Self Ltd | Health & social care | 2021 |
| Secure the Slay Ltd | Other services | 2023 |
| Secure-Plan Logistics Limited | Transport & logistics | 2025 |
| Security Alert UK Limited | Other services | 2002 |
| Security and Fire Engineering Limited | Administrative & support | 2022 |
| Security and Training Network Ltd | Administrative & support | 2026 |
| Security Gates 'R' US Limited | Manufacturing | 2020 |
| Security Holdings Limited | Financial services | 2003 |
| Security Revised Ltd | Extraterritorial | 2022 |
| SED Assured Care Limited | Health & social care | 2026 |
| Sedcaz Fashion Limited | Manufacturing | 2026 |
| SEE - Engagement Limited | Professional & scientific | 2017 |
| SEE Cars Nottingham Ltd | Wholesale & retail | 2015 |
| Seebun Property Group Ltd | Real estate | 2024 |
| Seeker Ecology Limited | Professional & scientific | 2022 |
| Seelath Property Services Ltd | Real estate | 2024 |
| Seerah Hajj and Umrah Limited | Administrative & support | 2024 |
| SEG3 Ltd | Information & communication | 2023 |
| Seguro Healthcare Ltd | Health & social care | 2026 |
| SEH Salon Ltd | Other services | 2015 |
| Sekhon Brothers Limited | Transport & logistics | 2019 |
| Sekhon Haulage Group Ltd | Financial services | 2024 |
| Sekhon Haulage Limited | Transport & logistics | 2016 |
| Sekhon Property Holdings Ltd | Real estate | 2024 |
| Sekhon Vehicles Ltd | Administrative & support | 2024 |
| Sekispeaks Limited | Education | 2018 |
| Sekna Ltd | Information & communication | 2024 |
| SEL Solutions Ltd | Transport & logistics | 2003 |
| Sela Engineering Limited | Professional & scientific | 2004 |
| Selah Giftware Ltd | Manufacturing | 2020 |
| Select LAB Services Ltd | Health & social care | 2026 |
| Select Midlands Limited | Wholesale & retail | 2026 |
| Selective Solutions Consultancy Limited | Other services | 2016 |
| Self Address Limited | Hospitality | 2009 |
| Self and Team Consulting Limited | Professional & scientific | 2012 |
| Self Exclusion Limited | Public administration | 2023 |
| Self Worth Care Ltd | Health & social care | 2022 |
| Selina Properties Management Ltd | Real estate | 2024 |
| Sellar Services Limited | Extraterritorial | 2001 |
| Sellars Farms Ltd | Agriculture & fishing | 1997 |
| Sellek Hairdressing Limited | Other services | 2018 |
| Selloo Ltd | Information & communication | 2011 |
| Selric Ltd | Real estate | 2026 |
| SEM Consultancy Ltd | Professional & scientific | 2024 |
| Semantic Minds Ltd | Information & communication | 2025 |
| Semper Primus Ltd | Health & social care | 2023 |
| Semplete Ltd | Wholesale & retail | 2021 |
| SEN Support Ltd | Education | 2022 |
| Sen-Fit CIC | Education | 2022 |
| Senad Community Limited | Health & social care | 1998 |
| Senad Holdings Limited | Education | 2004 |
| Senad Investments Limited | Administrative & support | 2006 |
| Senad Limited | Education | 1974 |
| Senator International Freight Forwarding Limited | Transport & logistics | 1994 |
| Send From Abroad Ltd | Wholesale & retail | 2021 |
| Sendacar Ltd | Transport & logistics | 2023 |
| Sendik Ltd | Information & communication | 2017 |
| Sendisco CIC | Other services | 2022 |
| Seniorman Network CIC | Information & communication | 2025 |