| Sdaniel Real Estate Ltd | Real estate | 2023 |
| SDB Drilling Services Limited | Construction | 2019 |
| SDC Propinvest Limited | Real estate | 2017 |
| SDI Properties Limited | Real estate | 2005 |
| SE7ENTEN Ltd | Information & communication | 2014 |
| Sea and Mountain (Europe) Limited | Real estate | 2014 |
| Sea and Mountain LLP | | 2023 |
| Seal Island Media Limited | Information & communication | 2011 |
| Seamless Conference and Events Limited | Administrative & support | 2012 |
| Seangi Electrical Ltd | Construction | 2023 |
| Seann Walsh Limited | Arts & recreation | 2011 |
| Seansadvertisements Ltd | Information & communication | 2024 |
| Seasons Grounds Care Limited | Other services | 2014 |
| Seawood House Ltd | Hospitality | 2026 |
| Second ARC Ltd | Arts & recreation | 2023 |
| Second Broom Barns Management Company Limited | Real estate | 1976 |
| Sectra Limited | Health & social care | 2002 |
| Sectra Products UK Limited | Information & communication | 2006 |
| Secugi Security Services UK Ltd. | Administrative & support | 2016 |
| Secure Engineering Limited | Administrative & support | 1995 |
| Secure Glaze & Locks Ltd | Construction | 2026 |
| Security Focus Limited | Administrative & support | 2007 |
| Seecom Limited | Administrative & support | 2012 |
| Seeka Limited | Professional & scientific | 2021 |
| Segcom Ltd | Construction | 2015 |
| SEH Supply & Hire Ltd | Administrative & support | 2016 |
| SEJ1986 Limited | Wholesale & retail | 2025 |
| SEL Subsidiary Limited | Extraterritorial | 2012 |
| Selcy Investments Limited | Real estate | 1955 |
| Select Design Interiors Limited | Construction | 1998 |
| Select Scaffolding Services Limited | Construction | 2015 |
| Selectatest Limited | Professional & scientific | 2010 |
| Selector Media Ltd | Professional & scientific | 2025 |
| Selekt (Hitchin) Limited | Administrative & support | 2019 |
| Selyer Technician Ltd | Manufacturing | 2019 |
| Sema Media Ltd | Professional & scientific | 2016 |
| Semota Limited | Real estate | 2023 |
| Send Angels | Transport & logistics | 2023 |
| Send Operative Solutions Ltd | Administrative & support | 2023 |
| Send Yogis CIC | Education | 2023 |
| Sensorstack Ltd | Extraterritorial | 2024 |
| Sentry Court Hitchin Ltd | Real estate | 2011 |
| Sentrya Payroll Ltd | Professional & scientific | 2026 |
| Seoai Digital Ltd | Professional & scientific | 2025 |
| SEP & Poore Ltd | Administrative & support | 2015 |
| Sequential Care Limited | Health & social care | 2017 |
| Serenity Health & Care Services Ltd | Public administration | 2020 |
| Serenity Locums Limited | Administrative & support | 2019 |
| Sermo Mediation and Legal Services Ltd | Professional & scientific | 2026 |
| Serpable Holdings Limited | Financial services | 2021 |
| Serpable Ltd | Information & communication | 2017 |
| Serper Ltd | Financial services | 2026 |
| Serve First Group Ltd | Health & social care | 2024 |
| Serve Home Care Ltd. | Health & social care | 2019 |
| Serve Property Management Ltd | Real estate | 2025 |
| Serverchoice Holdings Ltd | Financial services | 2024 |
| Serverchoice Ltd | Information & communication | 2021 |
| Servicetec Airport Services International Limited | Information & communication | 2000 |
| Servicetec Employee Share Scheme Company Limited | Financial services | 1998 |
| Servicetec Global Services Limited | Information & communication | 2003 |
| SET FIX Ltd | Construction | 2022 |
| Seva Realty Ltd | Real estate | 2019 |
| Seventhree (73) Camera Support Limited | Arts & recreation | 2014 |
| Sewardstone Road(Block B)Management Company Limited | Households | 1985 |
| Seyvee Ltd | Health & social care | 2022 |
| SF Imaging Ltd | Health & social care | 2022 |
| SF Voice & Accent Limited | Arts & recreation | 2019 |
| SG Artists Ltd | Arts & recreation | 2016 |
| SG Country Contractors Ltd | Agriculture & fishing | 2024 |
| SG Healthcare Ltd | Health & social care | 2012 |
| SG Launderette Services Limited | Other services | 2025 |
| SG Medical GP Services Limited | Health & social care | 2026 |
| SG Records Limited | Other services | 2020 |
| SG1 K9 Services Limited | Agriculture & fishing | 2022 |
| SG1SCOMMS Ltd | Information & communication | 2017 |
| SG2 Estates Ltd | Real estate | 2023 |
| SGA Construct Ltd | Construction | 2022 |
| Sgbl Limited | Arts & recreation | 2016 |
| Sgblb Events Limited | Other services | 2022 |
| Sggp Locum Limited | Health & social care | 2022 |
| SGV Trans Limited | Transport & logistics | 2019 |
| SHA Social Ltd | Information & communication | 2026 |
| Shadel Private Ltd | Financial services | 2025 |
| Shades of LDN Ltd | Wholesale & retail | 2019 |
| Shahfy Limited | Professional & scientific | 2022 |
| Shail Aesthetics Limited | Health & social care | 2016 |
| Shamrock Agencies Ltd | Professional & scientific | 2005 |
| Shanakill Limited | Real estate | 2013 |
| Shankara Investments Limited | Real estate | 2020 |
| Sharman's Legal Consultancy Limited | Professional & scientific | 2023 |
| Sharpstack Hosting Limited | Information & communication | 2016 |
| Shaughnessy Electrical Ltd | Construction | 2026 |
| Shcf LLP | | 2006 |
| She's a REC' Ltd | Arts & recreation | 2021 |
| Shedfield Services Ltd | Health & social care | 2015 |
| Shefford Footcare Limited | Health & social care | 2017 |
| Shel Solutions Limited | Construction | 2021 |
| Shelby Consulting Ltd | Professional & scientific | 2019 |
| Shelkov Consulting Limited | Information & communication | 2022 |
| Shellco Ltd | Construction | 2023 |