| Second Chance Retail Ltd | Administrative & support | 2017 |
| Secret Source Talent Solutions Ltd | Administrative & support | 2024 |
| Sector Cars Limited | Wholesale & retail | 2022 |
| Secure Access Solutions Limited | Construction | 2012 |
| Secure Development Insights Ltd | Professional & scientific | 2024 |
| Secure Entrance Systems Limited | Administrative & support | 2021 |
| Secure Prints Limited | Professional & scientific | 2008 |
| Secure Properties Group Ltd | Real estate | 2025 |
| Secure Storage by Anji’S Limited | Real estate | 2010 |
| Secure Vending Limited | Manufacturing | 2022 |
| Secure Xpress Logistics Ltd | Transport & logistics | 2023 |
| Secured Solutions Ltd | Wholesale & retail | 2022 |
| Secureit Plus Services Ltd | Administrative & support | 2018 |
| Secureit Services (MCR) Ltd | Other services | 2021 |
| Securesmartly Ltd | Administrative & support | 2019 |
| Securi Network Limited | Real estate | 2020 |
| Security in Focus Ltd | Professional & scientific | 2022 |
| Security Solutions (Northern) Ltd | Manufacturing | 2003 |
| Security Solutions (Southern) Limited | Construction | 2005 |
| Security Task Force UK Limited | Administrative & support | 2025 |
| Securyze Limited | Other services | 2025 |
| Sedao Consultancy Ltd | Professional & scientific | 2020 |
| Seddon Building Limited | Extraterritorial | 2013 |
| Seddon Care Partnerships Limited | Construction | 2010 |
| Seddon Comprop Limited | Real estate | 2025 |
| Seddon Construction Limited | Construction | 1998 |
| Seddon Developments Limited | Construction | 2000 |
| Seddon Electrical Ltd | Construction | 2017 |
| Seddon Energy Limited | Extraterritorial | 2011 |
| Seddon Energy Solutions Limited | Extraterritorial | 2011 |
| Seddon Engineering Finance Limited | Financial services | 2024 |
| Seddon Engineering Holdings Limited | Professional & scientific | 2013 |
| Seddon Engineering Services Ltd | Construction | 2011 |
| Seddon Estates Limited | Extraterritorial | 2013 |
| Seddon Grasscroft (Foxdenton) Limited | Construction | 2011 |
| Seddon Green Energy Limited | Extraterritorial | 2011 |
| Seddon Group Limited | Professional & scientific | 2013 |
| Seddon Housing Partnerships Limited | Construction | 2013 |
| Seddon Investments Limited | Real estate | 2016 |
| Seddon Maintenance Limited | Extraterritorial | 2013 |
| Seddon Painting & Maintenance Limited | Construction | 2013 |
| Seddon Painting Limited | Extraterritorial | 2015 |
| Seddon Properties Limited | Extraterritorial | 2013 |
| Seddon Property Services Limited | Construction | 2013 |
| Seddon RDP Limited | Construction | 2011 |
| Seddon Renewables Limited | Extraterritorial | 2011 |
| Seddon Securities Limited | Extraterritorial | 2013 |
| Seddon Solar Limited | Extraterritorial | 2013 |
| Seddon Solutions Limited | Extraterritorial | 2014 |
| Seddons (Plant and Engineers) Limited | Wholesale & retail | 1951 |
| Seddons Construction Limited | Extraterritorial | 2011 |
| Sedrick Limited | Administrative & support | 2023 |
| SEE BEE DEE Limited | Wholesale & retail | 2026 |
| SEE Mediah Limited | Professional & scientific | 2020 |
| SEE the Bigger Picture Limited | Other services | 2018 |
| SEE U Optical Ltd | Construction | 2024 |
| SEE Whats Possible Limited | Professional & scientific | 2023 |
| Seeb Appliances Limited | Wholesale & retail | 2025 |
| Seed and Solace Limited | Information & communication | 2022 |
| Seekers Apparel Limited | Wholesale & retail | 2025 |
| Seekers IP Ltd | Administrative & support | 2022 |
| Seep Limited | Information & communication | 2014 |
| Seepenny Ltd | Hospitality | 2018 |
| Sehnaz Natha Limited | Real estate | 2016 |
| Seiber Limited | Information & communication | 2017 |
| Seicos Courier Ltd | Transport & logistics | 2025 |
| Seilawelding Ltd | Manufacturing | 2025 |
| Selby Court Management Company Limited | Households | 2004 |
| Selby Decorators Ltd | Construction | 2015 |
| Seld Marketing Limited | Administrative & support | 2021 |
| Select and Save Services Limited | Administrative & support | 2017 |
| Select and Save Superstore Burnley Limited | Wholesale & retail | 2019 |
| Select Consultancy Limited | Professional & scientific | 2022 |
| Select Design Publishing Limited | Professional & scientific | 2011 |
| Select Interiors NW Ltd | Construction | 2026 |
| Select Motor Company Ltd | Wholesale & retail | 2025 |
| Select NW Limited | Professional & scientific | 2025 |
| Select Travel Media Limited | Professional & scientific | 1997 |
| Select Valeting Limited | Administrative & support | 2002 |
| Selectavan Ltd | Wholesale & retail | 2024 |
| Selfless Cosmetics Ltd | Other services | 2021 |
| Sell Your Machines Ltd | Wholesale & retail | 2024 |
| Seller UNI Ltd | Professional & scientific | 2024 |
| SELLER711 Ltd | Wholesale & retail | 2025 |
| Sellerbuzz Ltd | Transport & logistics | 2019 |
| Sellert UK Ltd | Wholesale & retail | 2024 |
| Sellertree Ltd | Wholesale & retail | 2019 |
| Sellgorithms Ltd | Wholesale & retail | 2026 |
| Selling IT ALL Ltd | Wholesale & retail | 2023 |
| Sellistra Limited | Wholesale & retail | 2025 |
| Selot & Sons Ltd | Wholesale & retail | 2020 |
| Seltej Services Limited | Health & social care | 2015 |
| Selwyn Jans Ltd | Information & communication | 2017 |
| Sema Advisory Ltd | Information & communication | 2019 |
| Semamed Ltd | Wholesale & retail | 2022 |
| Semimakeovers Limited | Construction | 2013 |
| Semiseke Health Ltd | Health & social care | 2022 |
| Sempertech Ltd | Manufacturing | 2026 |
| Sempoi Foods Ltd | Wholesale & retail | 2026 |
| SEN2GETHERUK CIC | Health & social care | 2026 |