| Simple Roofing & Cleaning Ltd | Construction | 2025 |
| Simply Bathrooms Peterborough Limited | Wholesale & retail | 2008 |
| Simply Produce Ltd | Wholesale & retail | 2011 |
| Simply Roofing Cleaning Services Ltd | Construction | 2026 |
| Simstan Limited | Transport & logistics | 2015 |
| Sinclair Knight Capital Ltd | Financial services | 2025 |
| Singlesole Farm Limited | Financial services | 2021 |
| Sinilo Trans Ltd | Transport & logistics | 2017 |
| Sisson Refrigeration Services Limited | Extraterritorial | 2021 |
| Site Pulse Ltd | Professional & scientific | 2026 |
| Site Watch Group Limited | Administrative & support | 2024 |
| Siuntos TT Ltd | Transport & logistics | 2024 |
| SIX Oaks Ltd | Agriculture & fishing | 2017 |
| Siyoto Cares Ltd | Health & social care | 2018 |
| SJC Stanberry Limited | Construction | 2021 |
| SJJ Electrical Services | | 1992 |
| SJM Auto Services Limited | Wholesale & retail | 2009 |
| SJS Marine Consultants Ltd | Professional & scientific | 2023 |
| SJS Multitrade Ltd | Administrative & support | 2019 |
| SK Electrical Solutions Ltd | Professional & scientific | 2003 |
| SK Roofing and Guttering Ltd | Construction | 2024 |
| SK UK Trans Ltd | Transport & logistics | 2023 |
| SKD Building Services Limited | Construction | 2007 |
| Skegy Ltd | Transport & logistics | 2018 |
| SKH Innovations Limited | Financial services | 2025 |
| Skin-Nav Ltd | Wholesale & retail | 2026 |
| Skippers Piece Close Management Company Limited | Households | 2024 |
| Skoulikas Bedford Limited | Wholesale & retail | 1990 |
| Skwpa Ltd | Transport & logistics | 2021 |
| Sky Roofing 1 Ltd | Construction | 2026 |
| Skycraft Limited | Wholesale & retail | 1990 |
| Skyedrip Ltd | Wholesale & retail | 2025 |
| Skyforge Holdings Ltd | Professional & scientific | 2025 |
| Skylark HGV Ltd | Transport & logistics | 2018 |
| SLA K Transport Ltd | Transport & logistics | 2025 |
| Slack Holdings Ltd | Financial services | 2023 |
| Slator Bros.(Farms)Limited | Agriculture & fishing | 1959 |
| Slator Creative Ltd | Arts & recreation | 2023 |
| Slavi Trans Limited | Transport & logistics | 2015 |
| Slawomir Chrzanowski Ltd | Transport & logistics | 2019 |
| Sledzik Ltd | Transport & logistics | 2024 |
| Sleeping Disorders Centre Harley Street Limited | Health & social care | 2014 |
| Sleeping Disorders Centre Limited | Health & social care | 2009 |
| Sleeping Disorders Centre London Limited | Health & social care | 2014 |
| Sleight Energy Limited | Construction | 2019 |
| Slice of Life Photography Limited | Professional & scientific | 2026 |
| Slice&Ice Ltd | Hospitality | 2024 |
| Slimming World With Alex Ltd | Other services | 2026 |
| Slingshot Buyout Limited | Administrative & support | 2013 |
| Slip MAT Heaven Limited | Wholesale & retail | 2025 |
| Slir LLP | | 2020 |
| SLM Interior Furnishings Ltd | Professional & scientific | 2023 |
| Slsuk Limited | Administrative & support | 2025 |
| SLW Property Ltd | Real estate | 2020 |
| SLW Property Services Limited | Real estate | 2010 |
| SLY Bros. (Potatoes) Limited | Agriculture & fishing | 1955 |
| Smalley Hot TUB Services Ltd | Manufacturing | 2020 |
| Smart Autoworx Limited | Wholesale & retail | 2024 |
| Smart Homes Property Maintenance Ltd | Construction | 2022 |
| Smart Homes Roof Cleaning Ltd | Construction | 2023 |
| Smart Protection Ltd | Administrative & support | 2019 |
| Smart Tax and Business Consulting Ltd | Professional & scientific | 2018 |
| Smart Tech (Nottingham) Ltd | Construction | 2019 |
| SMB Fire Safety Limited | Wholesale & retail | 2008 |
| Smith & Munson Limited | Agriculture & fishing | 1949 |
| Smith Bros Holdings Ltd | Real estate | 2026 |
| Smiths Solutions Ltd | Wholesale & retail | 2025 |
| Smiths Transport (Spalding) Ltd | Transport & logistics | 2013 |
| SMS Autospray Ltd | Wholesale & retail | 2021 |
| SMT Wood Burning Stoves Ltd | Wholesale & retail | 2012 |
| Smth Solutions Ltd | Professional & scientific | 2010 |
| Smudge Fitness Limited | Arts & recreation | 2020 |
| Snais Group Ltd | Wholesale & retail | 2026 |
| Snaith Flowers Limited | Agriculture & fishing | 2022 |
| Snaith Holdings Limited | Financial services | 2025 |
| Snak Trans Ltd | Wholesale & retail | 2015 |
| Snarskis Capital Ltd | Real estate | 2019 |
| Snarskis Media Ltd | Professional & scientific | 2021 |
| Sneath's Mill Trust Ltd | Arts & recreation | 2007 |
| SO Prop Ltd | Real estate | 2025 |
| Socius Limited | Administrative & support | 2016 |
| Soft Rock Living Limited | Real estate | 2025 |
| Software Everything Limited | Information & communication | 2016 |
| Software Primitives Limited | Information & communication | 2014 |
| Solafide Healthcare Ltd | Health & social care | 2019 |
| Solarcap Limited | Energy | 2012 |
| Solohead Maintenance Ltd | Construction | 2026 |
| Solution 61 Ltd | Wholesale & retail | 2020 |
| Solwing Cargo Ltd | Transport & logistics | 2013 |
| Sonder House Creative Ltd | Information & communication | 2024 |
| Sophia Services Ltd | Transport & logistics | 2018 |
| Sophia Thain Ltd | Other services | 2024 |
| Sorin Haulage Services (SHS) Ltd | Transport & logistics | 2021 |
| Sorin Santa Ltd | Transport & logistics | 2017 |
| Sorin Transport Ltd | Transport & logistics | 2014 |
| Sorina Limited | Transport & logistics | 2018 |
| South Downs Sporting Club Ltd | Arts & recreation | 2021 |
| South East Lincolnshire Hydrotherapy and Grooming Limited | Professional & scientific | 2021 |
| South Holland Air Conditioning Ltd | Construction | 2023 |
| South Holland Brewing Company Ltd | Wholesale & retail | 2026 |