| Sighthound Ltd | Professional & scientific | 2025 |
| Sigma Homes (Angmering) Limited | Construction | 2016 |
| Sigma Homes (Cuckfield) Limited | Construction | 2017 |
| Sigma Homes (Fittleworth) Ltd | Construction | 2016 |
| Sigma Homes (Haywards Heath) Limited | Construction | 2016 |
| Sigma Homes (Horsham) Limited | Construction | 2017 |
| Sigma Homes (Investments) Ltd | Real estate | 2026 |
| Sigma Homes (Maresfield) Ltd | Construction | 2020 |
| Sigma Homes (Thames Ditton) Ltd. | Construction | 2017 |
| Sigma Homes Limited | Construction | 2012 |
| Sigma Strategic Land Limited | Real estate | 2019 |
| Sigmatiqa Ltd | Manufacturing | 2024 |
| Signal Communications Limited | Administrative & support | 2017 |
| Signal Hill Partnership Ltd. | Administrative & support | 2017 |
| Signals Data Group Limited | Information & communication | 2026 |
| Signatia Ltd | Arts & recreation | 2024 |
| Signature Crest Homes Ltd | Construction | 2024 |
| Signet Interiors Ltd | Professional & scientific | 2024 |
| Signify Commercial UK Limited | Manufacturing | 1934 |
| Signseen Limited | Manufacturing | 2000 |
| Signseen Sign Services Limited | Manufacturing | 2025 |
| Sikani Ltd | Real estate | 2023 |
| Silent Kitchen Ltd | Wholesale & retail | 2026 |
| Silicon Gene Ltd | Information & communication | 2016 |
| Silicon Heath Ltd | Administrative & support | 2025 |
| Silver Bridge Education Limited | Education | 2026 |
| Silver Curve Limited | Information & communication | 2010 |
| Silver Link Haulage Ltd | Transport & logistics | 2026 |
| Silver Sun Music Ltd | Information & communication | 2026 |
| Silver Telecom Limited | Manufacturing | 1997 |
| Silverbridge Investments and Trading Limited | Wholesale & retail | 2016 |
| Silvergreen Energy Consultancy Ltd | Professional & scientific | 2014 |
| Silverleaf Spaces Ltd | Construction | 2020 |
| Simc Consultancy Ltd | Professional & scientific | 2021 |
| Simmons Court Management Company Limited | Households | 2019 |
| Simon Alexander Estates Ltd | Real estate | 2025 |
| Simon Best Associates Limited | Professional & scientific | 2015 |
| Simon Property Solution Ltd | Construction | 2014 |
| Simon-Building Construction Ltd | Construction | 2018 |
| Simple Eats Limited | Hospitality | 2024 |
| Simple Revolution Limited | Professional & scientific | 2018 |
| Simpli Technology Group Ltd | Information & communication | 2023 |
| Simplified Services Ltd | Administrative & support | 2020 |
| Simply Commercial Vehicles Ltd | Wholesale & retail | 2023 |
| Simply Interim Consulting Limited | Professional & scientific | 2009 |
| Simply Orthodontics Guildford Ltd | Health & social care | 2016 |
| Simply Vinyl Records Limited | Wholesale & retail | 2023 |
| Simplylet.Net (Guildford) Ltd | Real estate | 2018 |
| Simpson Studio Ltd | Professional & scientific | 2013 |
| Sinclair Energy Limited | Professional & scientific | 2013 |
| Sinclair Johnston & Partners Limited | Professional & scientific | 2003 |
| Singh Collaborative Ltd | Health & social care | 2021 |
| Singh Concrete Ltd | Manufacturing | 2014 |
| Singhtech Limited | Information & communication | 2017 |
| Sink Emporium Limited | Wholesale & retail | 2016 |
| Sips & Giggles Ltd | Hospitality | 2023 |
| Sirius Cleaning Services Ltd | Administrative & support | 2017 |
| Sirus U.K. Limited | Professional & scientific | 2020 |
| Sisaf Ltd | Professional & scientific | 2006 |
| Sisupeople. Limited | Administrative & support | 2020 |
| Sivast Limited | Administrative & support | 2011 |
| Siviter & Studio Ltd | Professional & scientific | 2026 |
| SIX Stages Framework Limited | Real estate | 2022 |
| SJ Walmsley Consultancy Ltd | Other services | 2025 |
| SJA Digital Solutions Ltd | Other services | 2018 |
| SJP International Ltd | Other services | 2017 |
| SJR Accounting Ltd | Professional & scientific | 2018 |
| SJR Building Ltd | Construction | 2017 |
| SK Building & Landscaping Ltd | Construction | 2026 |
| Sketch Force Ltd | Information & communication | 2024 |
| SKI Coach Ltd | Education | 2014 |
| Skin Farm Limited | Wholesale & retail | 2023 |
| Skipping Events Ltd | Education | 2026 |
| Skqs Limited | Professional & scientific | 2009 |
| Skullcandy UK Limited | Other services | 2017 |
| Sky Expert Witness Limited | Health & social care | 2024 |
| Sky High Solutions Property Ltd | Real estate | 2017 |
| Skylar International Ltd | Financial services | 2015 |
| Skylar Mauritius Investments LLP | | 2015 |
| Skylife Pro Ltd | Information & communication | 2015 |
| Skymax Containers Ltd | Wholesale & retail | 2025 |
| Skyout Limited | Real estate | 2016 |
| Skypostal UK Limited | Professional & scientific | 2006 |
| SL97 Limited | Other services | 2019 |
| SL97 Properties Ltd | Real estate | 2023 |
| Slades Farm BNG Limited | Professional & scientific | 2024 |
| Slaidburn 52 Limited | Construction | 2015 |
| Slate to Summit Limited | Information & communication | 2025 |
| Slice of PIE Limited | Hospitality | 2013 |
| Slightly MAD Studios Limited | Information & communication | 2008 |
| Slightly Pretty Limited | Information & communication | 2016 |
| Slim Line Drain Ltd | Wholesale & retail | 2026 |
| Slowave Therapeutics Ltd | Professional & scientific | 2020 |
| Slowburn Interactive Ltd | Information & communication | 2023 |
| SLS Advisory Limited | Administrative & support | 2018 |
| SLS Fusion Ltd | Hospitality | 2021 |
| SLV Holdings Limited | Financial services | 2016 |
| Smallpablo Creative Limited | Professional & scientific | 2025 |
| Smallthorne Properties Limited | Real estate | 2013 |
| Smart Bunny Media Ltd | Information & communication | 2007 |