| Smart-Medic Limited | Health & social care | 2014 |
| Smartgrid Electrical Ltd | Construction | 2017 |
| Smartwash Laundry Ltd | Real estate | 2019 |
| Smartz Executive Ltd | Transport & logistics | 2025 |
| SME Serve Ltd | Professional & scientific | 2024 |
| Smileshore Ltd | Health & social care | 2025 |
| Smith Global Services UK Ltd | Wholesale & retail | 2022 |
| Smiths Concrete Limited | Mining & quarrying | 1957 |
| SMJ Innovation Ltd | Professional & scientific | 2017 |
| SMK Works Limited | Information & communication | 2026 |
| Smook Ltd | Information & communication | 2024 |
| Smooth Pictures Ltd | Professional & scientific | 2012 |
| Smoothstride Ltd | Manufacturing | 2025 |
| SMT Products Limited | Wholesale & retail | 2016 |
| SMW Slough Limited | Wholesale & retail | 2022 |
| SN Sohi Ltd | Extraterritorial | 2012 |
| Snail Porridge Limited | Information & communication | 2005 |
| Snap Vision Ltd | Professional & scientific | 2020 |
| Snaptax Limited | Professional & scientific | 2022 |
| SNB Consulting Ltd | Information & communication | 2019 |
| Snigdha Ltd | Information & communication | 2012 |
| Snodas Estates Ltd | Real estate | 2022 |
| Snodas Trading Ltd | Wholesale & retail | 2021 |
| Snow Leopard Cloud Consulting Limited | Information & communication | 2017 |
| SO Financial Ltd | Professional & scientific | 2025 |
| Social Climbers Collective Ltd | Professional & scientific | 2024 |
| Social Essence Media Ltd | Professional & scientific | 2025 |
| Sofanni Ltd | Wholesale & retail | 2025 |
| Sofia Cars Services Ltd | Wholesale & retail | 2022 |
| Soficas Limited | Professional & scientific | 2024 |
| Softools Limited | Information & communication | 1998 |
| Softspark Ltd | Information & communication | 2025 |
| Software Outsourcing Services SOS Limited | Information & communication | 2017 |
| Softworks Computing (UK) Limited | Information & communication | 2000 |
| Sogo Europe Limited | Professional & scientific | 2018 |
| Sojo Fitness Ltd | Extraterritorial | 2020 |
| Sojo Property Limited | Real estate | 2022 |
| Soka Gakkai International - UK | Other services | 2004 |
| Solaegis Group Ltd | Health & social care | 2025 |
| Solar Technics Limited | Construction | 2004 |
| Solar-Tech Scaffolding Ltd | Construction | 2026 |
| Solarfire Group Limited | Public administration | 2024 |
| Solario Enterprises Ltd | Manufacturing | 2008 |
| Sole Purpose Podiatry Limited | Health & social care | 2025 |
| Solenvis Limited | Professional & scientific | 2010 |
| Solid Property Maintenance Ltd | Construction | 2019 |
| Solid Software Solutions Limited | Information & communication | 2012 |
| Solidliquidity Ltd | Information & communication | 2025 |
| Solrec Limited | Professional & scientific | 1989 |
| Soltech Systems Limited | Administrative & support | 1999 |
| Solve Consulting Services Ltd | Professional & scientific | 2021 |
| Solved With Technology (SWT) Ltd | Information & communication | 2012 |
| Solves Travel Ltd | Administrative & support | 2020 |
| Somaomnia Ltd | Health & social care | 2008 |
| Somerlea Freehold Limited | Households | 2018 |
| Somersby Property Limited | Real estate | 2026 |
| Something Inc Limited | Professional & scientific | 2015 |
| Something Inc Ventures Limited | Professional & scientific | 2021 |
| Something Personal Limited | Wholesale & retail | 2010 |
| Soni Solutions Limited | Information & communication | 2007 |
| Sonia Cleans Ltd | Administrative & support | 2026 |
| Sonic Star Limited | Real estate | 2001 |
| Sonmar OC Ltd | Wholesale & retail | 2026 |
| Sonney Ltd | Information & communication | 2022 |
| Soothsayer Games Limited | Information & communication | 2014 |
| Sope UK CIC | Education | 2026 |
| Sorted Art Ltd | Arts & recreation | 2020 |
| SOS Clinic (Slough) Limited | Health & social care | 2018 |
| Sospel Consultants Ltd | Professional & scientific | 2021 |
| Sotira Trading LLP | | 2009 |
| Soulcal Ltd | Information & communication | 2016 |
| Sound and Song CIC | Education | 2022 |
| Sound Identity Ltd | Arts & recreation | 1987 |
| Sound Impressions Ltd | Administrative & support | 1996 |
| Soundly Grounded Ltd | Wholesale & retail | 2024 |
| Soundwire Ltd | Information & communication | 2016 |
| South African Sunshine Limited | Wholesale & retail | 2006 |
| South Bucks Services Limited | Administrative & support | 2013 |
| South Central Transfers Limited | Transport & logistics | 2024 |
| South Central Vehicles Limited | Administrative & support | 2024 |
| South East Consulting Limited | Administrative & support | 2007 |
| South East Land Holdings Limited | Real estate | 2024 |
| South Isle Consulting Limited | Professional & scientific | 2025 |
| South of Sahara Imports Ltd | Wholesale & retail | 2024 |
| South West Coffee Ltd. | Hospitality | 2008 |
| South Western Property Services Ltd | Construction | 2014 |
| Southern North Estates Ltd | Real estate | 2019 |
| Southern West Estates Ltd | Real estate | 2019 |
| Southern Yard Co Ltd | Real estate | 2025 |
| Southside Electrical Solutions Limited | Construction | 2018 |
| Sovereign Electrical Services Limited | Construction | 2000 |
| Sovrano Consultancy Limited | Professional & scientific | 2020 |
| SP Films Ltd | Information & communication | 2014 |
| SP Innovations Management Limited | Information & communication | 2022 |
| SP247 Ltd | Information & communication | 2015 |
| Spacebar Media Limited | Professional & scientific | 2005 |
| Spark Analysis Limited | Information & communication | 2020 |
| Spark TCG Ltd | Wholesale & retail | 2025 |
| Sparkbay Limited | Financial services | 2019 |
| Sparkle Berkshire Limited | Administrative & support | 2025 |