| Sirkular Ltd | Information & communication | 2024 |
| Sirocco Hospitality Limited | Real estate | 2022 |
| Sirocco Services Ltd | Information & communication | 2024 |
| Sirs Only Ltd | Other services | 1997 |
| Sisdit Ltd | Manufacturing | 2017 |
| Sish.Ai Ltd | Information & communication | 2025 |
| Sissta Sissta Hair Care Ltd | Wholesale & retail | 2024 |
| Sistars Emporium Ltd | Wholesale & retail | 2018 |
| Sisu Reformer Pilates Limited | Other services | 2025 |
| Site Social Ltd | Information & communication | 2026 |
| Site Solutions Specialist Contractors Limited | Construction | 2019 |
| Site Trading Company (Fermanagh) Limited | Real estate | 2013 |
| Sitelines UK Limited | Construction | 2003 |
| Siterexx Limited | Public administration | 2019 |
| Sites for Business Limited | Professional & scientific | 2014 |
| Sitesolved Rubbish & House Clearance Limited | Water & waste | 2018 |
| Sitestone Surveying Ltd | Professional & scientific | 2026 |
| SIV Estates Ltd | Real estate | 2026 |
| Siva Cafe Ltd | Hospitality | 2026 |
| Siva Group Holdings Limited | Financial services | 2022 |
| Siva Group Ltd | Construction | 2025 |
| Siva Logistics Ltd | Construction | 2025 |
| Siva Property Investments Limited | Real estate | 2024 |
| Sivo Enterprises Ltd | Public administration | 2024 |
| Siwy Paint Ltd | Wholesale & retail | 2025 |
| Sixsess Ltd | Professional & scientific | 2020 |
| Sixth Sense Marketing Ltd | Professional & scientific | 2014 |
| Siyah Limited | Hospitality | 2020 |
| Sizzleasia Ltd | Manufacturing | 2025 |
| SJ Cladding&Carpentry Ltd | Construction | 2022 |
| SJ Consultancyb Ltd | Professional & scientific | 2023 |
| SJ Electric Ltd | Construction | 2022 |
| SJ Exotic Store Ltd | Wholesale & retail | 2023 |
| SJ Holdings & Maintenance Ltd | Real estate | 2026 |
| SJ Imaging and Eyewear Limited | Wholesale & retail | 2025 |
| SJ Marine Services Ltd | Transport & logistics | 2023 |
| SJ Savage Building & Property Maintenance Ltd | Construction | 2018 |
| SJ Walsh Limited | Administrative & support | 2017 |
| SJB Brickwork Ltd | Construction | 2019 |
| SJB Heating & Plumbing Ltd | Energy | 2017 |
| SJB P&H Ltd | Construction | 2018 |
| SJD Communications Limited | Other services | 2015 |
| SJD Electrical Solutions Limited | Construction | 2026 |
| SJE Consulting Ltd. | Professional & scientific | 2007 |
| SJG Container Handling Limited | Transport & logistics | 2020 |
| SJG Containers Limited | Transport & logistics | 2021 |
| SJG Haulage Limited | Manufacturing | 2006 |
| SJG Properties South Limited | Households | 2021 |
| SJK Furness Building Contractors Limited | Construction | 2011 |
| SJL Dragon Ltd | Hospitality | 2023 |
| SJM Consultancy Ltd | Professional & scientific | 2024 |
| SJM Deliveries Ltd | Transport & logistics | 2025 |
| SJM Spice Limited | Hospitality | 2024 |
| SJN Transport Ltd | Transport & logistics | 2018 |
| SJT Services (Southampton) Limited | Construction | 2015 |
| SJU Equine Ltd | Arts & recreation | 2024 |
| SJV Services Ltd | Transport & logistics | 2022 |
| SJW GAS Services Limited | Construction | 2018 |
| SK Barber Hamble Ltd | Other services | 2023 |
| SK Bros Logistics Ltd | Transport & logistics | 2025 |
| SK Dalyan Ltd | Other services | 2023 |
| SK Global Trade Ltd | Wholesale & retail | 2024 |
| SK Property Services 01 Ltd | Construction | 2021 |
| SK Sholing Ltd | Other services | 2024 |
| SK South Properties Ltd | Real estate | 2025 |
| SK Store Front Ltd | Wholesale & retail | 2025 |
| SK Taxi Hire Ltd | Transport & logistics | 2018 |
| Sk/N Brows & Beauty Ltd | Other services | 2021 |
| SK108 Limited | Hospitality | 2025 |
| Skaadams Solutions Ltd | Health & social care | 2017 |
| Skaiy Limited | Information & communication | 2025 |
| Skale Properties Limited | Real estate | 2024 |
| Skamp Hospitality Limited | Other services | 2020 |
| Skarriotplus Ltd | Health & social care | 2024 |
| Skclub Ltd | Hospitality | 2026 |
| Skeptron Properties Inc Ltd | Real estate | 2017 |
| Skerdilaid Property Limited | Real estate | 2020 |
| Skerrols Property Company Limited | Real estate | 1972 |
| Sketchbox Group Ltd | Wholesale & retail | 2020 |
| SKI Composites Ltd | Manufacturing | 2021 |
| Skill Build Construction Ltd | Construction | 2015 |
| Skill Guardian Training Ltd | Education | 2026 |
| Skill Scaffolding Limited | Construction | 1992 |
| Skilllynk Consulting Ltd | Information & communication | 2025 |
| Skills for Business Training Limited | Administrative & support | 2009 |
| Skillworks Learning Ltd | Education | 2026 |
| Skilton Group Limited | Financial services | 2020 |
| Skiltoncourt Limited | Real estate | 1978 |
| Skin & Strands Limited | Wholesale & retail | 2024 |
| Skin Aesthetics & Academy Ltd | Health & social care | 2025 |
| Skin Deep Rejuvenation Therapies Ltd | Health & social care | 2019 |
| Skin Marshall Ltd | Health & social care | 2025 |
| Skincare Inc Ltd | Other services | 2021 |
| Skinny KID Ltd | Information & communication | 2019 |
| Skintastic Aesthetic Lasers Limited | Education | 2024 |
| Skintastic Aesthetic Supplies Ltd | Other services | 2017 |
| Skkop Ltd | Transport & logistics | 2025 |
| Skma Martial Arts Limited | Education | 2020 |
| Skoroda Ltd | Construction | 2018 |
| Skpm Investments Ltd | Real estate | 2024 |