| Siralex Limited | Transport & logistics | 2018 |
| Siren Sounds Events UK Ltd | Arts & recreation | 2026 |
| Sirha Consultancy Ltd | Professional & scientific | 2026 |
| Sirhind Ltd | Health & social care | 2022 |
| Sirhowy Enterprise Way (Holdings) Limited | Professional & scientific | 2003 |
| Sirhowy Enterprise Way Limited | Construction | 2003 |
| Siri Cars Limited | Wholesale & retail | 2026 |
| Sirius Growth Global Ltd | Real estate | 2018 |
| Sirius Model Making Limited | Arts & recreation | 2012 |
| Sirius Technology Ltd | Information & communication | 2019 |
| Sirvan Chicos Ltd | Hospitality | 2023 |
| Siscon Global Ltd | Construction | 2026 |
| Sison Artisan Limited | Hospitality | 2025 |
| Sisonke Global Transport Consultancy(Sgtc) Ltd | Transport & logistics | 2022 |
| Sispal Design Limited | Information & communication | 2021 |
| Sissons Depot Holdings Limited | Real estate | 2015 |
| Sissons Depot Limited | Real estate | 2015 |
| Sissons Estates Limited | Real estate | 2018 |
| Sissons Limited | Real estate | 2015 |
| Sissons of Sherburn Holdings Limited | Financial services | 2015 |
| Sissons Properties Limited | Financial services | 2015 |
| Sissy & Co Properties Ltd | Real estate | 2025 |
| Sista Hood Aesthetics Ltd | Health & social care | 2020 |
| Sistacare Ltd | Health & social care | 2021 |
| Sister Print Limited | Manufacturing | 2019 |
| Sistren Developments Limited | Construction | 2024 |
| Sisu Holdings Limited | Real estate | 2017 |
| SIT Consulting Services Ltd | Information & communication | 2024 |
| Site Data Specialists Limited | Professional & scientific | 2020 |
| Site Electrics (Leeds) Limited | Construction | 2006 |
| Site Rescue Limited | Health & social care | 2015 |
| Site Safety Construction Products Ltd | Wholesale & retail | 2008 |
| Sitech LLC Limited | Information & communication | 2025 |
| Sitecherish Ltd | Information & communication | 2026 |
| Sitekey Solutions Limited | Administrative & support | 2016 |
| Sitelogic Limited | Information & communication | 2025 |
| Sithuthe Health Care Ltd | Health & social care | 2019 |
| Sivaraj Consulting Services Ltd | Professional & scientific | 2015 |
| SIX Acre House Management Limited | Households | 2016 |
| SIX CS Care Agency Ltd | Transport & logistics | 2018 |
| Sixc Limited | Professional & scientific | 2013 |
| Sixpoint Motors Ltd | Wholesale & retail | 2024 |
| Sixrock Limited | Real estate | 2025 |
| Sixteennine Ltd | Other services | 2023 |
| Sixth Dimension Properties (Leeds) Limited | Real estate | 2019 |
| Sixty Five Consult Ltd | Professional & scientific | 2011 |
| Sixx Beauty Ltd | Other services | 2024 |
| Siya RAM Properties Ltd | Real estate | 2024 |
| Sizenet International Limited | Financial services | 2010 |
| Sizzling Ste's Limited | Hospitality | 2024 |
| SJ Cubed Consulting Ltd | Professional & scientific | 2021 |
| SJ Health and Aesthetics Ltd | Other services | 2024 |
| SJ Investment Properties Limited | Real estate | 2021 |
| Sj's Property Maintenance Ltd | Administrative & support | 2016 |
| SJ18 Limited | Real estate | 2018 |
| SJA Construction Solutions Limited | Administrative & support | 2023 |
| Sjal Limited | Financial services | 2015 |
| Sjam Consultancy Limited | Professional & scientific | 2017 |
| SJB Property Solutions Limited | Real estate | 2025 |
| SJB Urocare Ltd | Health & social care | 2015 |
| Sjcg Limited | Real estate | 2022 |
| SJD Goods Limited | Manufacturing | 1987 |
| Sjdg Ltd | Hospitality | 2024 |
| SJE Systems Limited | Information & communication | 2014 |
| SJH Recovers Ltd | Other services | 2024 |
| SJH Upholstery Ltd | Other services | 2024 |
| SJI Developments Limited | Construction | 2019 |
| SJI7 Sports Management Limited | Arts & recreation | 2007 |
| Sjjm Lifts Limited | Professional & scientific | 2020 |
| SJK Networks Ltd | Information & communication | 2018 |
| SJK Private Hire Limited | Transport & logistics | 2011 |
| SJM Assets Limited | Financial services | 2012 |
| SJM Groundworks Limited | Construction | 2006 |
| SJM Properties (Yorkshire) Limited | Administrative & support | 2018 |
| Sjmann Consulting Ltd | Wholesale & retail | 2023 |
| SJP Medical Locums Ltd | Health & social care | 2021 |
| SJP Transport Limited | Transport & logistics | 2020 |
| Sjpubco Ltd | Hospitality | 2026 |
| SJR Bioconsulting Ltd | Professional & scientific | 2023 |
| SJR Commercial Finance Ltd | Financial services | 2019 |
| SJR Reporting Limited | Professional & scientific | 2026 |
| Sjrt Properties Ltd | Real estate | 2023 |
| SJS Alliance Ltd | Arts & recreation | 2024 |
| SJT Health & Wellbeing Ltd | Other services | 2022 |
| SJV Consulting (Leeds) Limited | Extraterritorial | 2015 |
| SJW Solutions in Partnership Limited | Professional & scientific | 2012 |
| Sjzm Ltd | Wholesale & retail | 2024 |
| SK & Sons Property Management Ltd | Financial services | 2023 |
| SK 133 Ltd | Hospitality | 2026 |
| SK Autoparts & Used Cars Ltd | Wholesale & retail | 2023 |
| SK Business Services Ltd | Wholesale & retail | 2019 |
| SK Consultancy (UK) Limited | Information & communication | 2013 |
| SK Daily Ltd | Wholesale & retail | 2024 |
| SK Education Consulting Limited | Administrative & support | 2023 |
| SK Electrician and Mechanic Limited | Wholesale & retail | 2026 |
| SK Environmental Consultants Limited | Real estate | 2014 |
| SK Fitness Ltd | Arts & recreation | 2014 |
| SK Food Private Limited | Hospitality | 2025 |
| SK Harehills Ltd | Wholesale & retail | 2023 |
| SK Immediate Local Labour Solutions Ltd | Professional & scientific | 2023 |