| Simon Bidco Limited | Financial services | 2015 |
| Simon Burnett Property Investments Limited | Real estate | 1999 |
| Simon C Worthington Financial Consulting Limited | Professional & scientific | 2024 |
| Simon Courier Ltd | Transport & logistics | 2025 |
| Simon FBA Retail Ltd | Wholesale & retail | 2025 |
| Simon Fearon Consultants Limited | Administrative & support | 2018 |
| Simon Gurney & Co Limited | Professional & scientific | 2011 |
| Simon LY Properties Ltd | Real estate | 2019 |
| Simon Mckeown Limited | Information & communication | 2006 |
| Simon Midco Limited | Financial services | 2015 |
| Simon Moran Properties Limited | Real estate | 1999 |
| Simon Pighills Limited | Information & communication | 2004 |
| Simon Rawson Travel Limited | Administrative & support | 2023 |
| Simon's Doors & Windows Ltd | Manufacturing | 2015 |
| Simona Barbulescu Healthcare Limited | Health & social care | 2018 |
| Simona's Cake City Ltd | Manufacturing | 2015 |
| Simonedserdriver Ltd | Transport & logistics | 2017 |
| Simpatico Investments Ltd | Financial services | 2022 |
| Simple & Sweet Kitchen Ltd | Manufacturing | 2025 |
| Simple Business Accounting Ltd | Professional & scientific | 2023 |
| Simple Displays Limited | Manufacturing | 2013 |
| Simple Foundry Ltd | Information & communication | 2025 |
| Simple Living Solutions Ltd | Extraterritorial | 2024 |
| Simple Logistics Group Ltd | Transport & logistics | 2025 |
| Simple Web & SEO Ltd | Information & communication | 2014 |
| Simplegirlmarketing Ltd | Professional & scientific | 2024 |
| Simply AI Ltd | Information & communication | 2019 |
| Simply Candy Ltd | Wholesale & retail | 2019 |
| Simply Capital Limited | Information & communication | 2023 |
| Simply Commerce Group Ltd | Professional & scientific | 2014 |
| Simply Commerce Recruitment Ltd | Administrative & support | 2013 |
| Simply Eyecare Ltd | Health & social care | 2019 |
| Simply Hearing Ltd | Wholesale & retail | 2017 |
| Simply K2 Limited | Education | 2011 |
| Simply Ladies Inc Limited | Other services | 2017 |
| Simply Lettings Leeds Ltd | Extraterritorial | 2009 |
| Simply Lifetime Mortgages Ltd | Financial services | 2019 |
| Simply Playgrounds Limited | Construction | 2012 |
| Simply Smiles Limited | Education | 2014 |
| Simply Swales Ltd | Real estate | 2025 |
| Simply VTS Ltd | Other services | 2019 |
| Simplybuzzybees Limited | Administrative & support | 2024 |
| Simplyperfectionxo Ltd | Wholesale & retail | 2025 |
| Simplyweight Ltd | Other services | 2009 |
| Simpson and Associates Limited | Professional & scientific | 2012 |
| Simpson Circle Ltd | Real estate | 2022 |
| Simpson Construction Management Ltd | Construction | 2025 |
| Simpson Millar LLP | | 2005 |
| Simpson Millar Trust Corporation Limited | Extraterritorial | 2016 |
| Simpson Roofing Ltd | Construction | 2021 |
| Simpson Templar Ltd | Professional & scientific | 2013 |
| Simpson's Auto Care Ltd | Wholesale & retail | 2025 |
| Simpsons Fold East RTM Company Limited | Households | 2024 |
| Simpsons Fold Management Company Limited | Real estate | 1996 |
| Simpsons Fold West RTM Company Limited | Households | 2024 |
| Simpsons Group Leeds Ltd | Transport & logistics | 2014 |
| Sims Corp Ltd | Real estate | 2020 |
| Sims Sourcing Ltd | Real estate | 2021 |
| Simspace Cyber UK Ltd | Information & communication | 2022 |
| Simspring Ltd | Real estate | 2025 |
| Simtab Ltd | Health & social care | 2021 |
| Simto LLP | | 2018 |
| Simtrack DPC Limited | Manufacturing | 2018 |
| Simurgh Engineering Solutions Ltd | Professional & scientific | 2018 |
| Simwool Property Management Limited | Real estate | 2019 |
| SIN Fitness Ltd | Other services | 2025 |
| Sinai Synagogue, Leeds | Other services | 2012 |
| Sinani Enterprise Ltd | Hospitality | 2025 |
| Sincere Digital Ltd | Administrative & support | 2021 |
| Sincere Psychotherapy Ltd | Health & social care | 2024 |
| Sinclair Estate Management Ltd | Construction | 2025 |
| Sindhavai Ltd | Hospitality | 2025 |
| Sindhu DEB UK Limited | Health & social care | 2013 |
| Sinergia Solutions Ltd | Information & communication | 2022 |
| Sing KEE Group Limited | Real estate | 2004 |
| Sing KO Limited | Wholesale & retail | 2015 |
| Sing Sing (Bakery) Ltd | Hospitality | 2021 |
| Sing Sing (Cash Carry) Ltd | Wholesale & retail | 2020 |
| Sing Wong Limited | Wholesale & retail | 2010 |
| Sing&K Ltd. | Hospitality | 2016 |
| Singh Construction and Property Developers Ltd | Construction | 2022 |
| Singh Financial Services Ltd | Administrative & support | 2017 |
| Singh News (Liverpool) Ltd | Wholesale & retail | 2016 |
| Singh's Indian Street Food Ltd | Hospitality | 2019 |
| Singh's Transport Ltd | Transport & logistics | 2024 |
| Singhato Ltd | Hospitality | 2018 |
| Single Minded Restaurants Ltd. | Hospitality | 2000 |
| Singsbury's Ltd | Extraterritorial | 2025 |
| Singularities Ltd | Information & communication | 2022 |
| SIP Global Limited | Wholesale & retail | 2025 |
| SIP IT Wine Ltd | Hospitality | 2016 |
| Siplinks Ltd | Information & communication | 2023 |
| Sipta Limited | Information & communication | 2024 |
| Sipwoks & Co Ltd | Manufacturing | 2019 |
| SIR Alexander Fleming Public House Limited | Hospitality | 2014 |
| SIR English Ltd | Information & communication | 2018 |
| SIR James Hill & Sons,Limited | | 1922 |
| SIR Peter Vardy Partnership KCP 1 L.P. | | 2007 |
| SIR Robert Ogden Estates Ltd | Real estate | 1964 |
| SIR William Craven Ltd | Hospitality | 2022 |