| Shrink York Ltd | Other services | 2022 |
| Shuzwan Home & Apparel Ltd | Wholesale & retail | 2025 |
| Siam Secrets Limited | Manufacturing | 2005 |
| Siblaris Ltd | Professional & scientific | 2025 |
| Sibs Catering Ltd | Manufacturing | 2024 |
| Sibsons Consultancy Ltd | Professional & scientific | 2024 |
| SID Brackley Builders Ltd | Construction | 2014 |
| Siddalls Limited | Real estate | 2002 |
| Sideshowbob Limited | Wholesale & retail | 2024 |
| Sidhu's Properties YO1 Ltd | Real estate | 2025 |
| Sidot Ltd | Information & communication | 2012 |
| Sienna&Co Ltd | Hospitality | 2025 |
| Sierra Dirtbike Tours Ltd | Arts & recreation | 2018 |
| Siga Commercial Ltd | Real estate | 2024 |
| Sightline Window Supply Ltd | Construction | 2025 |
| Siglo 8 Property Investment Limited | Real estate | 2024 |
| Sigma Silanus Limited | Hospitality | 2026 |
| Sign and Speak Ltd | Education | 2023 |
| Signalling Integration Specialist Ltd | Professional & scientific | 2024 |
| Signalling Support Services Ltd | Professional & scientific | 2021 |
| Signature Joinery & Carpentry Ltd. | Construction | 2025 |
| Signet Storage Ltd | Transport & logistics | 2024 |
| Signs York Ltd | Manufacturing | 2020 |
| SIGNS4LIFE Limited | Education | 2018 |
| Siham Ltd | Other services | 2012 |
| Silas 7 Ltd | Manufacturing | 2025 |
| Silindro Limited | Administrative & support | 2021 |
| Silk Car Valeting Ltd | Wholesale & retail | 2024 |
| Silk Hand Carwash Ltd | Wholesale & retail | 2026 |
| Silk Horizon Ltd | Administrative & support | 2016 |
| Silkwood Hair Studio Limited | Other services | 2002 |
| Silly Stuff for Sale Ltd | Wholesale & retail | 2025 |
| Siloview Ltd | Extraterritorial | 2025 |
| Silva Hawk Limited | Professional & scientific | 2024 |
| Silva Insolvency & Recovery Services Limited | Financial services | 2014 |
| Silvadale Limited | Construction | 2016 |
| Silvanos York Ltd | Hospitality | 2022 |
| Silver Birches Holdings Ltd | Real estate | 2020 |
| Silver Hill (Preston) Management Company Limited | Households | 2016 |
| Silver Pearl York Ltd | Hospitality | 2025 |
| Silver Spur Saloons Limited | Hospitality | 2025 |
| Silver Summit Property Limited | Real estate | 2019 |
| Silver Trend (UK) Ltd | Wholesale & retail | 2013 |
| Silverdoor Agency Limited | Professional & scientific | 2012 |
| Silverfox Property Maintenance Ltd | Households | 2021 |
| Silverline Travel Limited | Transport & logistics | 2021 |
| Silverpond Capital Limited | Professional & scientific | 2026 |
| Silverwood (Garforth) Management Company Limited | Households | 2022 |
| Simaq Consulting Ltd | Professional & scientific | 2003 |
| Simblemyne Ltd | Construction | 2025 |
| Simexon Limited | Information & communication | 2024 |
| Simon Bristow Transport Limited | Transport & logistics | 2015 |
| Simon Cowton Limited | Hospitality | 2015 |
| Simon Davis Flooring (Aylesbury) Limited | Construction | 2021 |
| Simon Errington Limited | Administrative & support | 2017 |
| Simon Eyles Coaching Limited | Professional & scientific | 2023 |
| Simon Morris Transport Limited | Transport & logistics | 2007 |
| Simon Richardson Handyman Services Ltd | Construction | 2026 |
| Simon Sykes Builders Limited | Construction | 2004 |
| Simon Thomas Jockey Agent Limited | Arts & recreation | 2019 |
| Simons Auto Services Ltd | Wholesale & retail | 2020 |
| Simplebridgeai Ltd | Information & communication | 2026 |
| Simpli Water Ltd | Water & waste | 2024 |
| Simply Better Homes Ltd | Construction | 2020 |
| Simply Cleaning York Limited | Administrative & support | 2023 |
| Simply Formations Limited | Professional & scientific | 2003 |
| Simply LPG Limited | Wholesale & retail | 2021 |
| Simply Roofing Services Limited | Construction | 2018 |
| Simplybeautyaroma Ltd | Wholesale & retail | 2023 |
| Simplygwenifer Ltd | Education | 2022 |
| Simplypro Ltd | Financial services | 2012 |
| Simplypro Medicus Ltd | Health & social care | 2019 |
| Simplypro Technology Ltd | Information & communication | 2017 |
| Simppla Limited | Professional & scientific | 2020 |
| Simpson & Wood Ltd | Construction | 2002 |
| Simpson (Belle House) Limited | Construction | 2021 |
| Simpson (Public Works) Limited | Construction | 2021 |
| Simpson (York) EST Trustee Limited | Extraterritorial | 2020 |
| Simpson (York) Holdings Limited | Construction | 1994 |
| Simpson (York) Limited | Construction | 1965 |
| Simpson Associates Information Services Limited | Information & communication | 1997 |
| Simpson Living Ltd | Health & social care | 2025 |
| Simpson Shopfitting Limited | Extraterritorial | 2000 |
| Simpsonbell Limited | Administrative & support | 2000 |
| Simpsons Bespoke Engineering Ltd | Professional & scientific | 2018 |
| Simur Barber Ltd | Other services | 2014 |
| SIN Miedo Limited | Real estate | 2022 |
| Singing for ALL With Jessa CIC | Arts & recreation | 2020 |
| Singular Constructs. Ltd | Construction | 2016 |
| Sinks-Taps.Com Limited | Wholesale & retail | 2007 |
| Sipnotic Ltd | Wholesale & retail | 2025 |
| SIR Jacobs UK Ltd | Wholesale & retail | 2024 |
| Sirius Business Solutions Limited | Professional & scientific | 2000 |
| Sissons Illegal Gambling Claims Ltd | Information & communication | 2025 |
| Sissons Indemnity Claims Ltd | Professional & scientific | 2024 |
| Sister Luxe Ltd | Wholesale & retail | 2025 |
| Sitc Holdings Limited | Hospitality | 2015 |
| Site Banners Ltd | Manufacturing | 2018 |
| Site Logistic Services Ltd | Transport & logistics | 2024 |
| Site Manuals Direct Ltd | Administrative & support | 2023 |