| Siennarome Limited | Financial services | 2026 |
| Sierra Midlands Property Development Limited | Construction | 2023 |
| Sifa Accounting Limited | Professional & scientific | 2025 |
| SIG ST Augustine Ltd | Real estate | 2020 |
| Sigil Consulting Limited | Professional & scientific | 2023 |
| Sigma Cold Ltd | | 2002 |
| Sigma Construction Ltd | Administrative & support | 2024 |
| Sign Windows Limited | Manufacturing | 2022 |
| Signage Factory Ltd | Wholesale & retail | 2024 |
| Signage Fashion UK Limited | Manufacturing | 2024 |
| Signal and Noise AI Ltd | Professional & scientific | 2026 |
| SIGNAL58 Ltd | Information & communication | 2019 |
| Signant Tax Limited | Professional & scientific | 2025 |
| Signature Bars Ltd | Wholesale & retail | 2020 |
| Signature Drinks Ltd | Wholesale & retail | 2020 |
| Signature Estates (U.K) Limited | Real estate | 2026 |
| Signature Exteriors Ltd. | Professional & scientific | 2017 |
| Signature Fleet Limited | Transport & logistics | 2026 |
| Signature Hair & Skin Clinic Leicester Ltd | Health & social care | 2026 |
| Signature Int'L Trading Company Ltd | Professional & scientific | 2020 |
| Signature Kitchens (Leicester) Ltd | Construction | 2024 |
| Signature Nursing Ltd | Health & social care | 2019 |
| Signature Plus Studio Ltd | Information & communication | 2024 |
| Signature Textiles Ltd | Manufacturing | 2018 |
| Signaturecare Services Ltd | Health & social care | 2026 |
| Signbuzz Limited | Extraterritorial | 2015 |
| Signet Cctv Ltd | Administrative & support | 2014 |
| Signfab (UK) Limited | Manufacturing | 2000 |
| Signing Network CIC | Administrative & support | 2011 |
| Signum Communications Limited | Extraterritorial | 2006 |
| Signum Corporate Communications Limited | Information & communication | 2002 |
| Signware System Ltd | Manufacturing | 2006 |
| SIH Properties Ltd | Real estate | 2026 |
| Sihra Enterprises Limited | Wholesale & retail | 2003 |
| Sihra Limited | Real estate | 2005 |
| Siil Consulting Ltd | Financial services | 2012 |
| Siiya Investments Limited | Real estate | 2023 |
| SIJ Computing Services Limited | Information & communication | 2012 |
| SIK Solutions Ltd | Real estate | 2024 |
| Sikaa Holdco Limited | Real estate | 2025 |
| Sikaa Holdings Limited | Real estate | 2021 |
| Sikandar Retailers Limited | Wholesale & retail | 2025 |
| Sikh Community Centre Limited | Other services | 2006 |
| Sikh Living Ltd | Real estate | 2024 |
| Sikh Motorcycle Club UK Ltd | Other services | 2022 |
| Sikna Ecomm Ltd | Wholesale & retail | 2025 |
| Sikotar Investments Ltd | Real estate | 2025 |
| Sikotar Ltd | Hospitality | 2026 |
| Sikotar Trading Ltd | Wholesale & retail | 2025 |
| SIL Ventures Ltd | Financial services | 2024 |
| Sila Consultancy Ltd | Information & communication | 2025 |
| Sila Strategic Consulting Ltd | Professional & scientific | 2021 |
| Silbury Homes Limited | Real estate | 2025 |
| Sildar Ltd | Administrative & support | 2016 |
| Sildorex Company Limited | Professional & scientific | 1987 |
| Sileby Cottage 2024 Ltd | Hospitality | 2024 |
| Sileby Fish Bar Limited | Hospitality | 2012 |
| Sileby Mill Boatyard Limited | Arts & recreation | 2007 |
| Sileby Town Rugby Football Club Limited | Other services | 2015 |
| Silica Infotech Limited | Information & communication | 2016 |
| Silicon Realtech Ltd | Real estate | 2023 |
| Silk and Spice Collective Limited | Wholesale & retail | 2025 |
| Silk Catering Ltd | Hospitality | 2022 |
| Silk Fashionwear Ltd | Manufacturing | 2019 |
| Silk Petals Boutique Ltd | Wholesale & retail | 2025 |
| Silk Route Project Management Limited | Construction | 2024 |
| Silks Investments Ltd | Real estate | 2021 |
| Silkstone Environmental Limited | Professional & scientific | 2000 |
| Sillett and Co Limited | Wholesale & retail | 2021 |
| Silo Sports Limited | Information & communication | 2025 |
| Silva Orthodontics Ltd | Health & social care | 2025 |
| Silver Birch Design Studio Ltd | Professional & scientific | 2025 |
| Silver Care 16 Plus Ltd | Health & social care | 2025 |
| Silver Clock Holdings Limited | Financial services | 2019 |
| Silver Cloud Accounting Ltd | Professional & scientific | 2010 |
| Silver Compass Consultancy Services Limited | Professional & scientific | 2025 |
| Silver Girl Ltd | Manufacturing | 2017 |
| Silver Globe Investments Ltd | Real estate | 2017 |
| Silver Guard Security Ltd | Administrative & support | 2025 |
| Silver Inc (Leic) Ltd | Manufacturing | 2017 |
| Silver Lady Cleaning Products Limited | Manufacturing | 2021 |
| Silver Line Auto Motors Ltd | Wholesale & retail | 2023 |
| Silver Maple Properties Ltd | Real estate | 2016 |
| Silver Plaza Ltd | Wholesale & retail | 2023 |
| Silver Ruby Limited | Manufacturing | 2017 |
| Silver Sapphire Property Ltd | Real estate | 2017 |
| Silver Spirits Limited | Wholesale & retail | 1993 |
| Silver Spoon Foods Limited | Hospitality | 2018 |
| Silver Star Garages Limited | Manufacturing | 2007 |
| Silver Star Global Investments Ltd | Real estate | 2019 |
| Silverback Sponsorship Ltd | Arts & recreation | 2020 |
| Silverbeck Properties Limited | Hospitality | 2000 |
| Silverfoks Ltd | Manufacturing | 2024 |
| Silverfox Building Consultancy Ltd | Construction | 2020 |
| Silverhurst Films Limited | Professional & scientific | 2024 |
| Silverkey Residentials Ltd | Real estate | 2024 |
| Silverleaf Healthcare Ltd | Public administration | 2026 |
| Silverline Admin Services Ltd | Administrative & support | 2017 |
| Silverline Auto Group Ltd | Wholesale & retail | 2025 |
| Silverside Healthcare Ltd | Health & social care | 2022 |