| Shipnectic Ltd | Wholesale & retail | 2025 |
| Shipp Builders Limited | Construction | 2005 |
| Shipyard Tattoo Ltd | Other services | 2026 |
| Shivim Ltd | Health & social care | 2013 |
| Shkodra Transport Ltd | Transport & logistics | 2019 |
| SHL Group Services Ltd | Construction | 2015 |
| Shlope Limited | Manufacturing | 2007 |
| Shock of the Lightning Ltd | Construction | 2015 |
| Shoeless JOE Limited | Wholesale & retail | 1984 |
| Shoesmith Logistics Limited | Transport & logistics | 2025 |
| Shogun Practical Karate LLP | | 2018 |
| SHOOTEE4 Limited | Health & social care | 2019 |
| Shop Smart World Ltd | Wholesale & retail | 2025 |
| Shopshivy Ltd | Wholesale & retail | 2025 |
| Shopwise Venture Limited | Real estate | 2024 |
| Shore Lane Limited | Real estate | 2012 |
| Short Snout Media Ltd | Information & communication | 2021 |
| Short Wyre Street Property Management Limited | Households | 2025 |
| Shotgate Garage Ltd | Wholesale & retail | 2011 |
| Shouksmith Financial Planning Ltd | Financial services | 2016 |
| Showcases UK Limited | Wholesale & retail | 2006 |
| Showme Collective Ltd | Wholesale & retail | 2026 |
| Showme Resources Limited | Wholesale & retail | 2021 |
| SHP Food Machinery Ltd | Wholesale & retail | 2011 |
| Shree Sainath Ltd | Education | 2023 |
| Shrewd Consulting Limited | Professional & scientific | 2023 |
| Shukru Properties Limited | Households | 2024 |
| SI Consultancy Services Ltd | Construction | 2019 |
| Si-Cu Designs Ltd | Professional & scientific | 2024 |
| Sibbons (Alresford) Limited | Construction | 1964 |
| Sibley Electrical Limited | Construction | 2000 |
| Sick Monkey Ltd | Manufacturing | 2026 |
| Sidecar Productions Limited | Arts & recreation | 2022 |
| Sidekick Agent Limited | Information & communication | 2025 |
| Sidex Rehab & Fitness Ltd | Health & social care | 2025 |
| Sidhusand Limited | Health & social care | 2024 |
| Sidlin Ltd | Administrative & support | 2016 |
| Sidmar Electrical Ltd | Construction | 2020 |
| Siebho Ltd | Professional & scientific | 2025 |
| Sigma Technology Services Limited | Professional & scientific | 2020 |
| Signace (Colchester) Limited | Administrative & support | 2011 |
| Signace Limited | Administrative & support | 2011 |
| Signal Rate Limited | Information & communication | 2025 |
| Signals Hall Street Chelmsford Limited | Households | 2013 |
| Signature Spice Ltd | Hospitality | 2026 |
| Signed Memorabilia Shop Ltd | Wholesale & retail | 2011 |
| Silent Financial Limited | Financial services | 2024 |
| Silikal UK Limited | Wholesale & retail | 2011 |
| Silk Marketing Limited | Information & communication | 2021 |
| Silk Pearce Group Limited | Arts & recreation | 2020 |
| Silk Pearce Limited | Arts & recreation | 1985 |
| Silky Barbers Ltd | Other services | 2025 |
| Silostop Agri Limited | Wholesale & retail | 1938 |
| Silva's Spices Ltd | Wholesale & retail | 2023 |
| Silver Corp UK Ltd | Wholesale & retail | 2026 |
| Silver Fang Software Ltd | Information & communication | 2024 |
| Silver FOX Tech Services Ltd | Manufacturing | 2016 |
| Silver Street Clinic Ltd | Health & social care | 2013 |
| Silverlink Care Agency Ltd | Administrative & support | 2025 |
| Silverlink Consultancy Ltd | Administrative & support | 2022 |
| Silveroak Care Group Ltd | Health & social care | 2026 |
| Silversands Limited | Information & communication | 1987 |
| Silverswap Ltd | Information & communication | 2026 |
| Silvertip Consultancy Ltd | Professional & scientific | 2025 |
| Silverwhale Limited | Hospitality | 2024 |
| Simaffexs Solutions Limited | Transport & logistics | 2025 |
| Simbiis Limited | Information & communication | 2013 |
| Simcott Group Limited | Extraterritorial | 2010 |
| Simex Ltd | Wholesale & retail | 2024 |
| Simhasya Properties Limited | Real estate | 2025 |
| Simion Finishing Ltd | Construction | 2019 |
| Simmons Building Services (Developments) Limited | Administrative & support | 2016 |
| Simmons Building Services (South East) Limited | Administrative & support | 2016 |
| Simmply Active Group CIC | Education | 2024 |
| Simmply Active Ltd | Education | 2025 |
| Simon Bacon Ltd | Health & social care | 2008 |
| Simon Baker Films Limited | Professional & scientific | 2011 |
| Simon Fisher Surgery Limited | Health & social care | 2016 |
| Simon Hope Ltd | Manufacturing | 2013 |
| Simon Jones CBT Limited | Administrative & support | 2015 |
| Simon Kleyn Limited | Health & social care | 2007 |
| Simon Mccabe Ltd | Arts & recreation | 2026 |
| Simon Morris (Ipswich) Limited | Wholesale & retail | 2007 |
| Simon Morris (Thorpe) Limited | Wholesale & retail | 2008 |
| Simon Reed Development Ltd | Information & communication | 2012 |
| Simon's Kitchens Ltd | Construction | 2009 |
| Simora Digital Ltd | Information & communication | 2025 |
| Simoss Ltd | Wholesale & retail | 2023 |
| Simple Beer Necessities Ltd | Wholesale & retail | 2022 |
| Simple Van Hire Ltd | Administrative & support | 2020 |
| Simplicit Ltd | Professional & scientific | 2015 |
| Simplive Ltd | Construction | 2025 |
| Simply Carpets and Flooring Limited | Construction | 2022 |
| Simply Drywall Limited | Construction | 2010 |
| Simply Easy Ltd | Information & communication | 2019 |
| Simply FCS Limited | Professional & scientific | 2022 |
| Simply Fixings Ltd | Wholesale & retail | 2025 |
| Simply Flourish Limited | Professional & scientific | 2026 |
| Simply Living Limited | Wholesale & retail | 2001 |
| Simply Practical Ltd | Professional & scientific | 2014 |