| Simply Serviced Ltd | Wholesale & retail | 2025 |
| Simply Students Essex Limited | Other services | 2022 |
| Simply Trans Limited | Transport & logistics | 2019 |
| Simpson & Summers Construction Limited | Construction | 2019 |
| Simpson Medico-Legal Limited | Professional & scientific | 2016 |
| Sindh Holding UK GLA Limited | Arts & recreation | 2023 |
| Sing IT Entertainments Limited | Arts & recreation | 2015 |
| Singerkach Views Limited | Information & communication | 2024 |
| Singnasium Ltd | Arts & recreation | 2022 |
| Singula VOW Limited | Financial services | 2025 |
| Sinochem Cargill Fertilizer Import Export Co., Ltd | Manufacturing | 2025 |
| Sinsere Limited | Wholesale & retail | 2026 |
| SIR Isaac's Artisan Coffee Ltd | Hospitality | 2020 |
| SIR John Lyon House Management Limited | Households | 2007 |
| Siri IT Consultancy Limited | Information & communication | 2015 |
| Sirius Casting Agency Ltd | Arts & recreation | 2018 |
| Sirmani Foods Ltd | Hospitality | 2019 |
| Sisters Nails & Beauty Limited | Other services | 2018 |
| Site Fabrications Hire Ltd | Administrative & support | 2022 |
| Site Fabrications Limited | Construction | 2009 |
| Site Safe Medicals Ltd | Health & social care | 2023 |
| Site Specific Limited | Professional & scientific | 2000 |
| Site Training Inspection & Compliance Service Limited | Construction | 2015 |
| Sitemarketeer Limited | Information & communication | 2004 |
| Siteone Property Services Ltd | Construction | 2024 |
| Sitescanner Ltd | Construction | 2020 |
| SIX Sigma IT Solutions Limited | Information & communication | 2009 |
| Sixty-Ten Arts Management Consulting Limited | Arts & recreation | 2021 |
| Siya Education Ltd | Education | 2018 |
| Siyyaras Ltd | Wholesale & retail | 2025 |
| Sizzling Thyme Events Ltd | Hospitality | 2025 |
| SJ Carter Transport Ltd | Transport & logistics | 2025 |
| SJ Childminder Ltd | Health & social care | 2026 |
| SJ Groundworks Limited | Construction | 2016 |
| SJ Riley Limited | Information & communication | 2017 |
| SJ Roberts Consultants Ltd | Professional & scientific | 2024 |
| Sjafitness Ltd | Arts & recreation | 2018 |
| SJB Media Ltd | Professional & scientific | 2021 |
| SJC Financial Planning Limited | Financial services | 2019 |
| SJH Homes Ltd | Real estate | 2025 |
| SJJ Investment Portfolio Ltd | Real estate | 2020 |
| SJM (Suffolk) Limited | Administrative & support | 2012 |
| SJM W & D Solution Consultants Limited | Information & communication | 2023 |
| SJP Mechanical Services Ltd | Construction | 2016 |
| SJP Properties (2021) Limited | Administrative & support | 2021 |
| SJR Garden Machinery Limited | Other services | 2023 |
| SJR Group Ltd | Construction | 2022 |
| SJT Carpentry Ltd | Construction | 2021 |
| SJW Independent Financial Management Limited | Financial services | 2018 |
| SK Bakes Ltd | Manufacturing | 2024 |
| SK Colchester Limited | Hospitality | 2022 |
| SK Procurement Limited Limited | Wholesale & retail | 2025 |
| SK Tiptree Ltd | Wholesale & retail | 2014 |
| SK68 Property Ltd | Real estate | 2025 |
| SKB Pharma Services Ltd | Wholesale & retail | 2022 |
| Skeels Brothers Limited | Construction | 2011 |
| SKG Active Care Ltd | Health & social care | 2022 |
| Skill Nexus Ltd | Administrative & support | 2025 |
| Skills and Training Engagement Programme (Step) CIC | Other services | 2022 |
| Skills Pathway Limited | Education | 2025 |
| SKILLS2MATCH Ltd | Information & communication | 2026 |
| Skin Envy Advanced Aesthetics Ltd | Health & social care | 2024 |
| Skin Envy Colchester Ltd | Other services | 2023 |
| Skin Principles Limited | Health & social care | 2024 |
| Skinrenewal Limited | Health & social care | 2019 |
| SKIP25 Ltd | Water & waste | 2025 |
| Skipper Companies Ltd | Professional & scientific | 2018 |
| Skirret Developments Limited | Construction | 2025 |
| Skirret Holdings Limited | Financial services | 2025 |
| Skirret Investments Limited | Real estate | 2025 |
| Sknspired Ltd | Other services | 2026 |
| SKRATCH18 Ltd | Arts & recreation | 2021 |
| SKS Procurement Limited | Wholesale & retail | 2024 |
| SKT Care Agency Ltd | Health & social care | 2025 |
| Sky Leasing Ltd | Administrative & support | 2023 |
| Sky Promotions Ltd | Administrative & support | 2025 |
| Skyandsandtravel Ltd | Administrative & support | 2025 |
| Skye Green Solutions Ltd | Administrative & support | 2022 |
| Skye Holiday Chalets Limited | Hospitality | 2018 |
| Skye Leisure Limited | Hospitality | 2021 |
| Skye Lodging Ltd | Hospitality | 2024 |
| Skye River Property Group Ltd | Real estate | 2025 |
| Skye's the Limit Tea Room Ltd | Hospitality | 2018 |
| Skyfront Limited | Financial services | 2019 |
| Skyhigh Snkrs & Clothing Ltd | Wholesale & retail | 2024 |
| Skylark Social Limited | Wholesale & retail | 2022 |
| Skylarks (Botesdale) Residents Management Company Limited | Households | 2023 |
| Skyline Real Estate Properties Ltd | Real estate | 2026 |
| Skymeadow Gallery Limited | Wholesale & retail | 2021 |
| Skysaver Flights Limited | Administrative & support | 2025 |
| Skyton Solutions Ltd | Real estate | 2025 |
| Skyz Stones UK Limited | Wholesale & retail | 2021 |
| SL Executive Limited | Other services | 2008 |
| SL41 Ltd | Real estate | 2023 |
| Slammed UK Events Limited | Administrative & support | 2015 |
| Slammeduk Ltd. | Administrative & support | 2014 |
| SLB Roads Ltd | Construction | 2019 |
| SLD Events Limited | Arts & recreation | 2021 |
| SLD Groundwork Ltd | Construction | 2019 |
| Sleek Fashion House Limited | Wholesale & retail | 2024 |