| Simic Advisory Limited | Professional & scientific | 2025 |
| Simken LLP | | 2011 |
| Simlyst Limited | Administrative & support | 2022 |
| Simon Birnie Construction Limited | Construction | 2015 |
| Simon Cooke Plumbing Ltd | Construction | 2023 |
| Simon Creeber Financial Planning Limited | Financial services | 2010 |
| Simon Ellis Estates Limited | Real estate | 2017 |
| Simon Gledhill Consulting Limited | Professional & scientific | 2001 |
| Simon Smiles Limited | Health & social care | 2014 |
| Simonh Consulting Services Limited | Information & communication | 2023 |
| Simple Fast Mortgage Ltd | Financial services | 2020 |
| Simplifi Solutions (EOT) Limited | Financial services | 2023 |
| Simplifi Solutions Limited | Information & communication | 2008 |
| Simplifinancials Limited | Professional & scientific | 2017 |
| Simply Compliant Ltd | Professional & scientific | 2026 |
| Simply Financial Control and Reporting Limited | Professional & scientific | 2022 |
| Simply Orthodontics Ltd | Health & social care | 2010 |
| Simply SAZ Creative Limited | Professional & scientific | 2026 |
| Simply Tutors Limited | Information & communication | 2023 |
| Simply TV UK Limited | Information & communication | 2025 |
| Simplyhestia Ltd | Wholesale & retail | 2021 |
| Simplytajweed Ltd | Education | 2021 |
| Simrah Ltd | Real estate | 2014 |
| Sims Real Estate Limited | Real estate | 2019 |
| Sinematic the Show Limited | Arts & recreation | 2025 |
| Sinergy Consultants Ltd | Professional & scientific | 2024 |
| Sinergy Group Ltd | Administrative & support | 2017 |
| Singhal Enterprises UK Ltd | Real estate | 2021 |
| Sini BI Limited | Information & communication | 2024 |
| Sinolo Management Services Ltd | Real estate | 2015 |
| Sinuous Limited | Professional & scientific | 2018 |
| SIP and Sush Ltd | Hospitality | 2025 |
| SIP Consulting Limited | Information & communication | 2025 |
| Sirgartan Holdings Ltd | Professional & scientific | 2022 |
| Sirgartan Therapeutics Limited | Professional & scientific | 2020 |
| SIS (Cheshire) Ltd | Arts & recreation | 2012 |
| Site-Pro.App Ltd | Information & communication | 2023 |
| Sitetracker UK Limited | Information & communication | 2018 |
| Siva Neurophysiology Consulting Ltd | Health & social care | 2023 |
| Sivasai Estates Ltd | Real estate | 2020 |
| SIX Five Zero Limited | Hospitality | 2014 |
| SIX Recruitment Limited | Administrative & support | 2006 |
| SIX Sided Development Limited | Professional & scientific | 2022 |
| SIX Stories Limited | Wholesale & retail | 2019 |
| SIX10 Project Services Limited | Professional & scientific | 2025 |
| SJ Ball Ltd | Wholesale & retail | 2020 |
| SJ Blankstone Limited | Wholesale & retail | 2015 |
| SJ Griffin Limited | Hospitality | 2025 |
| SJ Wilton Ltd | Health & social care | 2022 |
| SJC Financial Services Contracting Ltd | Professional & scientific | 2015 |
| SJF80 Engineering Limited | Professional & scientific | 2023 |
| SJH Data Services Limited | Administrative & support | 2017 |
| SJM Developments Limited | Construction | 1997 |
| Sjmm Premier Investments Limited | Financial services | 2019 |
| SJS Payrolls Limited | Professional & scientific | 2025 |
| SJW Instruments Limited | Professional & scientific | 2018 |
| SJW Orthodontics Ltd | Health & social care | 2018 |
| SK Calcio Limited | Professional & scientific | 2026 |
| SK PPT Management Ltd | Financial services | 2025 |
| SK1 Refuel Limited | Wholesale & retail | 2024 |
| SK13 Ltd | Real estate | 2019 |
| SK1N Dash Ltd | Other services | 2026 |
| Sk:Inspire Ltd | Health & social care | 2019 |
| SKA Green House Limited | Information & communication | 2024 |
| SKC Homes Ltd | Real estate | 2020 |
| Skelgill Professional Services Limited | Professional & scientific | 2026 |
| Skelton Garage Ltd | Wholesale & retail | 1979 |
| Sketch Design Flow Ltd | Information & communication | 2022 |
| Skina Laser Ltd | Health & social care | 2021 |
| Skinkis TM Ltd | Construction | 2025 |
| Skinny DAD Media Ltd | Information & communication | 2016 |
| Skinny Revolution Ltd | Other services | 2017 |
| Sklep Pieniazek Limited | Wholesale & retail | 2024 |
| Skmax Limited | Professional & scientific | 2025 |
| SKN Luxe Ltd | Other services | 2026 |
| Skouted Holdings Limited | Information & communication | 2023 |
| Sky Blue Financial Investments Limited | Financial services | 2017 |
| Sky Engineering Consulting Limited | Professional & scientific | 2026 |
| Sky Group Holdings Ltd | Financial services | 2026 |
| Sky Mavis UK PTE. Ltd | Information & communication | 2023 |
| Sky Trading Company Limited | Transport & logistics | 1993 |
| Skydogg Ltd | Real estate | 2020 |
| Skye & Co. UK Limited | Construction | 2007 |
| Skye Brownhill Limited | Wholesale & retail | 2025 |
| Skyline Block Management Limited | Real estate | 2021 |
| Skynet BI Ltd | Information & communication | 2011 |
| Skypaper Ltd | Professional & scientific | 2016 |
| Skypro Medical Products UK Ltd | Administrative & support | 2020 |
| Skyreach Technologies Ltd | Information & communication | 2026 |
| SL Talent Source Ltd | Professional & scientific | 2026 |
| Slate and Stone Gallery Ltd | Construction | 2024 |
| Slate Medicines UK Limited | Professional & scientific | 2026 |
| Slater Hogg & Howison Limited | Professional & scientific | 2004 |
| Slater Surveys Ltd | Professional & scientific | 2024 |
| Slatters Development Limited | Construction | 2014 |
| SLB Risk Consulting Limited | Professional & scientific | 2018 |
| SLD Optics Limited | Health & social care | 2024 |
| Sleepers Point (Nantwich) Management Company Limited | Administrative & support | 2006 |
| Sleepless (UK) Limited | Health & social care | 2013 |
| Slenderrapide UK Ltd | Health & social care | 2017 |