| SIL Care Services Ltd | Health & social care | 2025 |
| SIL Traders Limited | Administrative & support | 2025 |
| Sila 26 Ltd | Transport & logistics | 2026 |
| Sila Accounting & Finance Limited | Professional & scientific | 2019 |
| Sila Leeds Ltd | Transport & logistics | 2023 |
| Sila Northern Limited | Real estate | 2021 |
| Silasons Ltd | Wholesale & retail | 2011 |
| Silatec.Com Limited | Information & communication | 2000 |
| Silavita Ltd | Health & social care | 2018 |
| Silbprop Limited | Extraterritorial | 2021 |
| Silchrome Holdings Limited | Manufacturing | 2008 |
| Silencz Ltd | Wholesale & retail | 2026 |
| Silent Equity Ltd | Education | 2025 |
| Silent Industries Ltd | Wholesale & retail | 2024 |
| Silentlight Works Ltd | Wholesale & retail | 2025 |
| Silentzound Limited | Arts & recreation | 2022 |
| Siletti Studios Ltd | Wholesale & retail | 2026 |
| Silex World Ltd | Professional & scientific | 2022 |
| Silflo Limited | Administrative & support | 2024 |
| Silhouette Films International Limited | Information & communication | 1995 |
| Silhouette Pilates Ltd | Arts & recreation | 2026 |
| Silicon Infotech Limited | Information & communication | 2025 |
| Silicon Yorkshire Ltd | Administrative & support | 2020 |
| Silicone Sister Ltd | Real estate | 2019 |
| Silidur Ltd | Wholesale & retail | 2005 |
| Silk and Paddock Clothing Limited | Wholesale & retail | 2026 |
| Silk Delta Trading Ltd | Financial services | 2021 |
| Silk Mews Management Company Limited | Real estate | 2017 |
| Silk Road Supermarket Ltd | Hospitality | 2025 |
| Silkpoint Limited | Extraterritorial | 1980 |
| Silks Developments Ltd | Construction | 2024 |
| Silks Estates (Yorkshire) Ltd | Real estate | 2016 |
| Silkscreen Europe Limited | Wholesale & retail | 1994 |
| Silkstan Ltd | Administrative & support | 2024 |
| Silkstone Property Group Limited | Real estate | 2024 |
| Silkstone Residential Limited | Real estate | 2025 |
| Silkwood Motor Group Ltd | Wholesale & retail | 2024 |
| Silly Chef Ltd | Professional & scientific | 2025 |
| Silly Fish Learning Ltd | Education | 2018 |
| Silly Lemon Limited | Other services | 2007 |
| Silly Salmon Sports Ltd | Professional & scientific | 2023 |
| Silmen Ltd | Wholesale & retail | 2023 |
| Silv Business Limited | Administrative & support | 2025 |
| Silva Home Solutions Limited | Construction | 2019 |
| Silver Birch Developments Group Limited | Construction | 2017 |
| Silver City Investments Ltd | Real estate | 2016 |
| Silver FAN Limited | Extraterritorial | 2003 |
| Silver Grey Foliage Limited | Wholesale & retail | 2024 |
| Silver Grill Leeds Ltd | Hospitality | 2021 |
| Silver Horizon Foods Ltd | Hospitality | 2026 |
| Silver Hub Leeds Limited | Wholesale & retail | 2017 |
| Silver Hub Limited | Wholesale & retail | 2017 |
| Silver Lane Garage (Leeds) Limited | Wholesale & retail | 2012 |
| Silver Lattice Ltd | Information & communication | 2026 |
| Silver Lined AI Ltd | Information & communication | 2025 |
| Silver Oak Marketing Limited | Extraterritorial | 2016 |
| Silver QI Ltd | Arts & recreation | 2026 |
| Silver Recovery 24/7 Ltd | Transport & logistics | 2026 |
| Silver Sky (UK) Limited | Professional & scientific | 2013 |
| Silver Star Auto Services Ltd | Wholesale & retail | 2024 |
| Silver Tree Capital UK Limited | Real estate | 2024 |
| Silverback Capital Limited | Real estate | 2023 |
| Silverback Empire Ltd | Real estate | 2021 |
| Silverback Martial Arts Ltd | Arts & recreation | 2023 |
| Silverback Solution Consult Ltd | Education | 2026 |
| Silverbirch Outdoor Activities Ltd | Arts & recreation | 2019 |
| Silvercrest Estates Limited | Construction | 2014 |
| Silverdale Care Homes Limited | Health & social care | 2004 |
| Silverdale Complex Care Ltd | Health & social care | 2023 |
| Silverkey Investments Ltd | Real estate | 2023 |
| Silverlight & Copperpen Ltd | Health & social care | 2020 |
| Silverlinings Support Ltd | Health & social care | 2025 |
| Silvermere Haven Limited | Water & waste | 1987 |
| Silvers Deli Ltd | Hospitality | 2023 |
| Silversand Properties Ltd | Real estate | 2019 |
| Silverseam Holdings Ltd | Real estate | 2022 |
| Silverseam Ltd | Wholesale & retail | 2021 |
| Silverspring Properties Limited | Real estate | 2014 |
| Silverstone Building Consultancy (Leeds) Ltd | Administrative & support | 2018 |
| Silverstone Holdings Ltd | Financial services | 2023 |
| Silverstone Marketing Ltd | Professional & scientific | 2026 |
| Silvervase Ltd | Hospitality | 2020 |
| Silviocarvalho Limited | Transport & logistics | 2026 |
| Sima RAY Ltd | Arts & recreation | 2014 |
| Simanalytica Limited | Professional & scientific | 2019 |
| Simba & Co Creations Ltd | Real estate | 2025 |
| Simba Homes Limited | Construction | 2017 |
| Simba Living Ltd | Real estate | 2025 |
| Simba XV Ltd | Real estate | 2024 |
| Simco NO. 85 Limited | | 1982 |
| Simfit Limited | Arts & recreation | 2020 |
| Simian Ventures Limited | Administrative & support | 2009 |
| Simkaaa Ltd | Professional & scientific | 2025 |
| Simmer & Soak Kitchens & Bathrooms Limited | Wholesale & retail | 2010 |
| Simmonds Wakeman Developments Ltd | Construction | 2020 |
| Simmons Developments Limited | Real estate | 2004 |
| Simms Cardiology Limited | Health & social care | 2020 |
| Simo Law Firm Ltd | Professional & scientific | 2026 |
| Simon & Viliam Ltd | Construction | 2018 |
| Simon Bickler KC Limited | Professional & scientific | 2015 |