| Singer Developments Limited | Construction | 2017 |
| Singer Store Ltd | Wholesale & retail | 2025 |
| Singular Films Ltd | Information & communication | 2022 |
| SIR Robert Mcalpine (Holdings) Limited | Professional & scientific | 1992 |
| SIR Robert Mcalpine Capital Ventures (Holdings) Limited | Financial services | 2021 |
| SIR Robert Mcalpine Capital Ventures Group Holdings Limited | Financial services | 2021 |
| SIR Robert Mcalpine Capital Ventures Limited | Construction | 2015 |
| SIR Robert Mcalpine Enterprises Limited | Financial services | 1995 |
| SIR Robert Mcalpine Healthcare (Dawlish) Limited | Health & social care | 1997 |
| SIR Robert Mcalpine Limited | Construction | 1956 |
| SIR Robert Mcalpine Management Contractors Limited | Construction | 1974 |
| SIR Robert Mcalpine Pension Scheme Capital Ventures Limited | Professional & scientific | 2011 |
| Sirrus Financial Planning Ltd | Financial services | 2012 |
| SJ Broadcast Engineering Ltd | Information & communication | 2025 |
| Skipcom Limited | Water & waste | 2020 |
| Skruffs Limited | Other services | 2024 |
| Sky Structures Ltd | Construction | 2012 |
| Skyline Funding UK Limited | Real estate | 2023 |
| Skywood Cars Ltd | Wholesale & retail | 2023 |
| Slater Oakwood Trading Limited | Wholesale & retail | 2026 |
| SLC Chipperfield Ltd | Wholesale & retail | 2020 |
| Sleepless Studios Ltd. | Information & communication | 2011 |
| Sloane Young Limited | Extraterritorial | 2018 |
| SMA Future Consultancy Limited | Professional & scientific | 1987 |
| SMA Pallets Ltd. | Transport & logistics | 2011 |
| SMA Worldwide Ltd | Transport & logistics | 2000 |
| Smart Air Products Ltd | Administrative & support | 2021 |
| Smart International Ltd | Information & communication | 2023 |
| Smart Makers Ltd | Manufacturing | 2021 |
| Smart Travel Services Limited | Administrative & support | 2013 |
| Smart Worldwide Ltd | Wholesale & retail | 2012 |
| Smartbay Golf Limited | Arts & recreation | 2023 |
| Smash Social Limited | Professional & scientific | 2018 |
| Smirthwaite Consultancy Limited | Professional & scientific | 2016 |
| Smith & Latimer Limited | Construction | 1977 |
| Smith Garrett Group Ltd | Administrative & support | 2022 |
| SMS Law Limited | Other services | 2018 |
| SO Soft Designs Limited | Other services | 2015 |
| Soho Comedy Factory Ltd | Arts & recreation | 2025 |
| Solar Slate Limited | Energy | 2009 |
| Solid Work Ltd | Manufacturing | 2022 |
| Solwaybank Energy Limited | Energy | 2014 |
| Something Guitar Limited | Wholesale & retail | 2009 |
| Sorella Sisko Ltd | Wholesale & retail | 2020 |
| SOS Security Management Limited | Administrative & support | 2024 |
| South Sharpley Limited | Energy | 2010 |
| Southern Breeze Limited | Construction | 2016 |
| Southmead Freehold Ltd | Real estate | 2024 |
| Southmead Management Ltd | Real estate | 2026 |
| Spartan Change Champions Community Interest Company | Hospitality | 2023 |
| SPC Property Investments Limited | Real estate | 2022 |
| Speedyright Limited | Manufacturing | 1995 |
| Spennymoor Energy Storage Limited | Energy | 2019 |
| Spice Villege Indian Restaurant Ltd | Hospitality | 2019 |
| Spiral Blue Limited | Administrative & support | 2016 |
| Spot Light Rigging Ltd | Construction | 2021 |
| Squad Security Limited | Administrative & support | 2005 |
| Squawk Luggage Limited | Manufacturing | 2025 |
| SSA Recruitment Limited | Administrative & support | 2009 |
| Ssss Investment 3 Ltd | Real estate | 2013 |
| ST Breock Limited | Energy | 2012 |
| ST. Blaise (1998) Limited | Construction | 1986 |
| Stanley Group Holdings Limited | Financial services | 2021 |
| Stanley Handling Limited | Wholesale & retail | 1969 |
| Stanners Electrical Limited | Professional & scientific | 2012 |
| Star Control Services Ltd | Construction | 2022 |
| Star Magic Estates Ltd | Real estate | 2022 |
| Startcount Property Management Limited | Households | 1988 |
| Stedman Developments Limited | Construction | 2020 |
| Stedman Plumbing & Heating Limited | Construction | 2011 |
| Stedman Property Ltd | Real estate | 2021 |
| Steeple Solar Farm Limited | Energy | 2022 |
| Steeple Wind Farm Limited | Energy | 2023 |
| Stefmarinn Ltd | Transport & logistics | 2018 |
| Step Springfield Village Limited | Construction | 2018 |
| Sterling & Sons Limited | Financial services | 2024 |
| Sterling Accounting Solutions Ltd | Professional & scientific | 2011 |
| Sterling Capital Investment Properties Limited | Real estate | 2021 |
| Sterling Capital Investors Limited | Professional & scientific | 2016 |
| Sterling Construction Projects Limited | Construction | 2019 |
| Sterling Property Network Limited | Real estate | 2005 |
| Sterling Travel and Events Ltd | Administrative & support | 2024 |
| Stoic Sound Limited | Information & communication | 2020 |
| Stortford Fields (Parcel U) Management Company Limited | Households | 2024 |
| Stortford Fields (Parcels B&C) Management Company Limited | Households | 2025 |
| Stortford Fields Apartments (Parcel 8) Residents Managment Company Limited | Households | 2025 |
| Stortford Fields Apartments (Parcel U) Management Company Limited | Households | 2024 |
| Stowe Partners Ltd | Professional & scientific | 2024 |
| STR Investments Limited | Real estate | 2024 |
| Strawberry Pharma Ltd | Administrative & support | 2023 |
| Stream Defence Ltd | Professional & scientific | 2014 |
| Stream Marine Ltd | Energy | 2015 |
| Streamify Ltd | Information & communication | 2020 |
| Street Spice Ltd | Hospitality | 2020 |
| Stuart Mcelroy Limited | Financial services | 2015 |
| SUE Clarke SEN Limited | Education | 2024 |
| Suited Insure Ltd | Financial services | 2021 |
| Summit Structures Contracts Ltd | Construction | 2022 |
| Summit Structures Group Ltd | Construction | 2025 |
| Summit Structures Ltd | Construction | 2016 |