| Simepr Ltd | Information & communication | 2020 |
| Simham Limited | Real estate | 2013 |
| Simi's Bookstore Ltd | Wholesale & retail | 2026 |
| Simmons Technical Limited | Information & communication | 2019 |
| Simmz Ltd | Wholesale & retail | 2026 |
| Simon Rigby Services Limited | Transport & logistics | 2017 |
| Simon Sullivans, Adventures in Learning CIC | Education | 2025 |
| Simparcel Limited | Transport & logistics | 2024 |
| Simphi Limited | Real estate | 2015 |
| Simple IT Distribution Limited | Wholesale & retail | 2015 |
| Simple Platform Work Limited | Administrative & support | 2026 |
| Simple Sites Ltd | Professional & scientific | 2026 |
| Simplecart Ltd | Wholesale & retail | 2026 |
| Simplify Creative Limited | Professional & scientific | 2021 |
| Simplify Social Ltd | Information & communication | 2024 |
| Simplify Solutions Limited | Information & communication | 2012 |
| Simply Divine Products Ltd | Wholesale & retail | 2022 |
| Simply Made Marketing Ltd | Information & communication | 2025 |
| Simply Monitor Ltd | Information & communication | 2022 |
| Simply Online Accounting Ltd | Education | 2019 |
| Simply Residential (Sales & Lettings) Limited | Other services | 2010 |
| Simply Sofas (UK) Limited | Manufacturing | 2002 |
| Simply-Buy-Sale Limited | Wholesale & retail | 2024 |
| Simpoole Consulting Ltd | Professional & scientific | 2024 |
| Simpson Medical and Rehabilitation Limited | Health & social care | 2024 |
| Simpsons Food Mart Ltd | Hospitality | 2025 |
| Sims Solutions UK Ltd | Health & social care | 2022 |
| Simul AB Initio Limited | Administrative & support | 2012 |
| Sina Services Ltd | Health & social care | 2024 |
| Sincere Pathway Recruitments Limited | Administrative & support | 2025 |
| Sinclaire Holdings Ltd | Real estate | 2013 |
| Sinclaire Trading Ltd | Financial services | 2021 |
| Sincorp Property Ltd | Real estate | 2024 |
| Sing Along Waiters Limited | Arts & recreation | 2020 |
| Singh Traders (MCR) Ltd | Wholesale & retail | 2022 |
| Singh Consultants Ltd | Professional & scientific | 2025 |
| Singh Logistics Ltd | Transport & logistics | 2018 |
| Sinha Medical Services Limited | Health & social care | 2011 |
| Sintech Solutions Ltd | Wholesale & retail | 2023 |
| Sintra Property Developments Limited | Construction | 2017 |
| SIP Clinic Ltd | Health & social care | 2022 |
| Siraj Curry House Ltd | Hospitality | 2022 |
| Sircus Limited | Wholesale & retail | 2014 |
| Sirius Capital Contracts Limited | Professional & scientific | 2021 |
| Sirron Limited | Financial services | 2019 |
| Sister HUT Ltd | Manufacturing | 2022 |
| Sisu Project Ltd | Manufacturing | 2024 |
| Sital Holdings (Sale) Limited | Real estate | 2017 |
| Sital Holdings 1 Limited | Real estate | 2021 |
| Sital Holdings Limited | Real estate | 2016 |
| Sital Petroleum Ltd | Wholesale & retail | 2011 |
| Site Management Maesteg Limited | Construction | 2017 |
| Site Nvqs Ltd | Education | 2021 |
| Site Tank Limited | Administrative & support | 2003 |
| Site Testing Services (Nationwide) Ltd | Construction | 2018 |
| Sitriryoma Ltd | Wholesale & retail | 2019 |
| SIU Claims Ltd | Wholesale & retail | 2025 |
| SIU Utilities Ltd | Construction | 2022 |
| SIX Bells (Dorking) Limited | Construction | 2018 |
| SIX Chillies Limited | Professional & scientific | 2023 |
| SIX Shot Golf Limited | Education | 2025 |
| Sixteen Design Limited | Professional & scientific | 2020 |
| Sixty SIX Interiors Ltd | Wholesale & retail | 2024 |
| Sizalendaba Ltd | Other services | 2013 |
| Size House Village Management Limited | Households | 1982 |
| Sizzle Creative Agency Limited | Real estate | 2005 |
| Sizzle Media Ltd | Professional & scientific | 2024 |
| SJ Associates Northwest Ltd | Professional & scientific | 2023 |
| SJ Projects Limited | Information & communication | 2024 |
| SJ Services Group Ltd | Health & social care | 2021 |
| SJ Stars Consultancy Ltd | Professional & scientific | 2022 |
| Sj's Hair & Beauty Limited | Other services | 2013 |
| Sjaelland Holdings Limited | Financial services | 2024 |
| Sjames Transport Ltd | Transport & logistics | 2025 |
| SJB Lancashire Ltd | Transport & logistics | 2015 |
| SJC Property Investments Limited | Real estate | 2019 |
| SJC Referrals Limited | Professional & scientific | 2022 |
| SJF Consultants Limited | Information & communication | 2023 |
| SJF Joinery Limited | Construction | 2026 |
| SJF Venture Holdings Ltd | Real estate | 2024 |
| SJG Executive Travel Ltd | Transport & logistics | 2015 |
| SJH Prosthetics Limited | Health & social care | 2022 |
| SJH Recovery Services Limited | Transport & logistics | 2023 |
| SJM Haulage Limited | Transport & logistics | 2026 |
| SJM Sales Ltd | Wholesale & retail | 2021 |
| SJP Flooring Specialists Ltd | Construction | 2021 |
| SJR Hospitality Ltd | Hospitality | 2020 |
| SJR Trading Ltd | Wholesale & retail | 2022 |
| SJS Healthcare Ltd | Wholesale & retail | 2017 |
| SJS Transport Services Ltd | Transport & logistics | 2023 |
| SJW Driver Services Ltd | Transport & logistics | 2015 |
| SJZ Logistics Limited | Transport & logistics | 2017 |
| SK Business Consulting Ltd | Administrative & support | 2014 |
| SK Deliveries Ltd | Transport & logistics | 2019 |
| SK Driving Services Limited | Transport & logistics | 2024 |
| SK Ices Limited | Hospitality | 2024 |
| SK Investments & Consultants Limited | Administrative & support | 2021 |
| SK Investments (Bolton) Ltd | Real estate | 2023 |
| SK Logistics Solutions Limited | Transport & logistics | 2025 |
| SK Moore Premises Limited | Real estate | 2021 |