| Simply Chrono Ltd | Wholesale & retail | 2026 |
| Simply Commercial Kitchens Ltd | Manufacturing | 2024 |
| Simply Comms Ltd | Information & communication | 2024 |
| Simply Covered Limited | Financial services | 2023 |
| Simply Hampers UK Ltd | Wholesale & retail | 2024 |
| Simply Potty Ltd | Hospitality | 2024 |
| Simply Virtuous Bakes. Ltd | Manufacturing | 2020 |
| Simply Virtuous Limited | Information & communication | 2022 |
| Simpson's American Sweets Limited | Wholesale & retail | 2025 |
| Sindlesham Success Ltd | Transport & logistics | 2015 |
| Sinem Ahmet Ltd | Health & social care | 2025 |
| Singletons Transport Limited | Transport & logistics | 2010 |
| Sipsynergy Limited | Information & communication | 2011 |
| Siren Security Limited | Administrative & support | 2025 |
| Sirius House Residents Association Limited | Households | 1980 |
| Sisko Group Ltd | Construction | 2020 |
| Sistematica Holding Limited | Financial services | 2018 |
| Siteline Limited | Professional & scientific | 1995 |
| Siteserv Recycling (EFW) Limited | Water & waste | 2014 |
| Siteserv Recycling (NW) Limited | Water & waste | 2013 |
| Siteserv Recycling (Plant) Limited | Administrative & support | 2013 |
| Sittingbourne Specsavers Hearcare Limited | Wholesale & retail | 2007 |
| Sittingbourne Specsavers Limited | Wholesale & retail | 1997 |
| Sittingbourne Visionplus Limited | Wholesale & retail | 2001 |
| SIX Physio Limited | Professional & scientific | 2007 |
| SIX Point Media Ltd | Information & communication | 2019 |
| Six-O Transport Limited | Transport & logistics | 2001 |
| SIY Couriers Ltd | Transport & logistics | 2024 |
| SJ Cumber Ltd | Health & social care | 2011 |
| SJ Mortgages Ltd | Financial services | 2021 |
| SJ Wilkinson Maintenance Ltd | Manufacturing | 2026 |
| SJA Goalkeeping Limited | Arts & recreation | 2022 |
| SJC Brickwork Ltd | Real estate | 2018 |
| Sjdk Developments Ltd | Real estate | 2025 |
| SJJ Services Ltd | Construction | 2019 |
| SJM Electrical Systems Ltd | Construction | 2022 |
| SJM Wills & Associated Services Limited | Professional & scientific | 2016 |
| Sjp-Cfe Ltd | Financial services | 2017 |
| SJS Advisory Limited | Professional & scientific | 2019 |
| SJS Group Limited | Financial services | 2025 |
| SJS Systems Limited | Professional & scientific | 2014 |
| SJW Avionics Ltd. | Manufacturing | 2017 |
| Skado Limited | Professional & scientific | 2003 |
| Skardex Ltd | Information & communication | 2022 |
| Skayler Ltd | Information & communication | 2025 |
| Skelmersdale Specsavers Limited | Wholesale & retail | 1994 |
| Skelmersdale Visionplus Limited | Wholesale & retail | 1994 |
| SKI 2 Limited | Administrative & support | 2001 |
| Skipsbrickwork. Ltd | Construction | 2018 |
| Skipton Specsavers Limited | Wholesale & retail | 2004 |
| Skipton Visionplus Limited | Wholesale & retail | 2004 |
| SKM Retailer Limited | Wholesale & retail | 2024 |
| Sknhead Ltd | Health & social care | 2017 |
| Sky Five Limited | Professional & scientific | 2015 |
| Sky Investment Properties Ltd | Real estate | 2022 |
| Skybound Financial Planning Limited | Financial services | 1995 |
| Skycloud Ltd | Information & communication | 2020 |
| Skyline Southern Ltd | Construction | 2014 |
| SL Rental Southampton Limited | Real estate | 2013 |
| SLB Machining Ltd | Professional & scientific | 2019 |
| SLC Estates Ltd | Real estate | 2024 |
| Sleaford Specsavers Limited | Wholesale & retail | 2007 |
| Sleaford Visionplus Limited | Wholesale & retail | 2007 |
| Sleeping Bear Hotels Ltd | Hospitality | 2017 |
| Sleeping Bear Notels Ltd | Financial services | 2020 |
| Sleipnir Estates Limited | Real estate | 2025 |
| Slgx Services Ltd | Information & communication | 2014 |
| Slick Access Limited | Wholesale & retail | 2018 |
| SLM Property Management Ltd | Households | 2022 |
| Sloane Gardens CT LLP | | 2024 |
| Sloane Gardens Flat 16 LLP | | 2024 |
| Sloane Residential Limited | Households | 2019 |
| Sloth Ltd | Wholesale & retail | 2018 |
| Slough Specsavers Hearcare Limited | Wholesale & retail | 2025 |
| SLR Property Solutions Limited | Real estate | 2009 |
| Slrs Limited | Administrative & support | 2002 |
| SLS Property Ltd | Real estate | 2018 |
| Sludgebusters Limited | Extraterritorial | 1990 |
| SLW Financial Ltd | Professional & scientific | 2012 |
| SM Konsult Ltd | Administrative & support | 2023 |
| Small Fish Solutions Limited | Professional & scientific | 2026 |
| Smart Choice Consultancy Ltd | Professional & scientific | 2017 |
| Smart Choice Equity Release Ltd | Financial services | 2025 |
| Smart FOX Productions Ltd | Arts & recreation | 2018 |
| Smart Home Contractors Limited | Professional & scientific | 2012 |
| Smart Home IMP Ltd | Construction | 2020 |
| Smart Maintenance & Builds Limited | Construction | 2024 |
| Smart Minded Solutions (SMS) Ltd | Education | 2023 |
| Smart Outsourced Marketing Solutions Ltd | Professional & scientific | 2025 |
| Smart Rudder International Ltd | Wholesale & retail | 2021 |
| Smart Rudder Travel Ltd | Administrative & support | 2023 |
| Smart Search Technical Ltd | Administrative & support | 2024 |
| Smart Stitches Ltd | Other services | 2023 |
| Smart Tech Systems 24 Ltd | Construction | 2025 |
| Smartlouvre Technology Limited | Manufacturing | 1998 |
| SMD Construction Consultancy Limited | Professional & scientific | 2018 |
| SMD Group Manchester Ltd | Wholesale & retail | 2026 |
| SMD Project Management Ltd | Construction | 2022 |
| SMH 2024 Limited | Professional & scientific | 2024 |
| Smile Clearly Limited | Health & social care | 2025 |