| Seen Forever Ltd | Wholesale & retail | 2025 |
| Self Financial Services Ltd | Financial services | 2018 |
| Selwyn Consultancy Ltd | Professional & scientific | 2017 |
| Sensorcom Limited | Manufacturing | 2000 |
| Sentio Consulting Ltd | Professional & scientific | 2024 |
| Seostatix Limited | Professional & scientific | 2025 |
| SEP Painters Limited | Construction | 2025 |
| Sequent Solutions Ltd | Administrative & support | 2016 |
| Serenity Therapy Sudbury Limited | Health & social care | 2025 |
| Seven Hunters Ltd | Arts & recreation | 2021 |
| Sewing Machine World Limited | Wholesale & retail | 2009 |
| Shaaji Limited | Real estate | 2025 |
| Shabbey Road Ltd | Wholesale & retail | 1994 |
| Sharma Business Development Ltd | Information & communication | 2026 |
| Sharman Restaurant Holdings Limited | Hospitality | 2021 |
| Sharon Wayve Bennett Limited | Public administration | 2025 |
| Sharpe Event Management Ltd | Administrative & support | 2017 |
| Shattered Design Ltd | Professional & scientific | 2014 |
| Shaw Rentals and Development Ltd | Construction | 2024 |
| SHE Bills Them Ltd | Information & communication | 2026 |
| Shine on HCW Ltd | Other services | 2014 |
| Shoesmith Entertainment Limited | Arts & recreation | 2011 |
| Shoreside Groundworks & Landscapes Ltd | Construction | 2017 |
| Siiger Holding Limited | Financial services | 2017 |
| Silk & Maple Ltd | Wholesale & retail | 2020 |
| Silver Branch Consultancy Limited | Administrative & support | 2023 |
| Silver Drive Limited | Real estate | 2018 |
| Silver Lining Suffolk Limited | Health & social care | 2025 |
| Silver Monkey Marketing Limited | Administrative & support | 2023 |
| Silver Rain Games Ltd | Information & communication | 2019 |
| Silvicultural Systems Limited | Agriculture & fishing | 2005 |
| Simitree Ltd | Wholesale & retail | 2019 |
| Simnett Consulting Ltd | Information & communication | 2010 |
| Simon Greene Associates Limited | Information & communication | 2005 |
| Simon Lovejoy and Associates Limited | Professional & scientific | 2004 |
| Simonswhiteweddingcars Ltd | Transport & logistics | 2018 |
| Simplexability Ltd | Information & communication | 2021 |
| Simply Funky Food Limited | Hospitality | 2020 |
| Simply Sourcing Ltd | Administrative & support | 2006 |
| Sims Construction Limited | Construction | 2003 |
| Singer Interactive Limited | Information & communication | 1998 |
| Sisterlane Ltd | Wholesale & retail | 2026 |
| Sitemind Ltd | Professional & scientific | 2026 |
| SJB Mobile Motor Services Ltd | Wholesale & retail | 2023 |
| SJB Safety Consultants Ltd | Health & social care | 2015 |
| SJC Accountants Ltd | Professional & scientific | 2026 |
| SJO Electrical Ltd | Construction | 2021 |
| SJP Risk Management Ltd | Professional & scientific | 2025 |
| Skalka Property Holdings Limited | Real estate | 2023 |
| Skalka Property Investments Limited | Financial services | 2023 |
| Skepsis Learning Ltd | Professional & scientific | 2019 |
| Skillother Limited | Transport & logistics | 1987 |
| Sky Meadows Ltd | Administrative & support | 2023 |
| Sky Windows (U.K.) Limited | Construction | 2003 |
| Slingersuk Ltd | Hospitality | 2026 |
| SM Sudbury Food Ltd | Hospitality | 2025 |
| SM Unified Solutions Limited | Wholesale & retail | 2024 |
| SM2 Construction Limited | Construction | 2019 |
| SMA Plastics Limited | Professional & scientific | 2021 |
| Smart Holistics Limited | Health & social care | 2005 |
| Smart Thinking Electrical Ltd | Construction | 2018 |
| Smcc Limited | Construction | 2005 |
| Smith & Ransome Limited | Hospitality | 2025 |
| Smith’S Construction Services Ltd | Construction | 2023 |
| Smoke and Poke Ltd | Administrative & support | 2026 |
| Snow Union Limited | Administrative & support | 2012 |
| Social Worker Direct Limited | Professional & scientific | 2008 |
| Softpure Life Ltd | Construction | 2025 |
| Solar Works Limited | Construction | 2001 |
| SOLE2SANCTUARY Ltd | Wholesale & retail | 2026 |
| Sophie Bird Beauty & Aesthetics Ltd | Other services | 2022 |
| Sorge Enterprises Ltd | Financial services | 2017 |
| Sorokin Pictures Limited | Information & communication | 2021 |
| Sorrelle Holdings Limited | Professional & scientific | 2003 |
| Sorrelle Services Limited | Wholesale & retail | 2017 |
| Sorrelle Transport Ltd | Transport & logistics | 2018 |
| Sorrelle Vehicle Sales Limited | Wholesale & retail | 2003 |
| Sosso Ltd | Information & communication | 2010 |
| Soultribe Music Ltd | Wholesale & retail | 2023 |
| Sound Research Laboratories Ltd | Extraterritorial | 2011 |
| Soundunit Limited | Manufacturing | 1988 |
| South East Blue Group Limited | Professional & scientific | 2015 |
| South Staffs Surveys Limited | Professional & scientific | 2003 |
| South Suffolk Developments Ltd | Real estate | 2016 |
| Southwold (High Street) Management Company Limited | Real estate | 2001 |
| Spa Court (Freehold) Limited | Real estate | 2008 |
| Spa Court Management (Block a) Limited | Households | 1990 |
| Spa Court Management (Block B) Limited | Households | 1990 |
| Sparktakular Ltd | Information & communication | 2009 |
| Specshop Limited | Wholesale & retail | 1982 |
| Spectrum Electrical (Sudbury) Limited | Construction | 2009 |
| Spiderhire Ltd | Extraterritorial | 2014 |
| Spingold Design & Print Ltd | Professional & scientific | 2013 |
| Splendid Productions Limited | Professional & scientific | 2013 |
| Splinters Caterers Ltd | Hospitality | 2026 |
| Sports Capture Limited | Arts & recreation | 2024 |
| Sports Mentoring Limited | Arts & recreation | 2011 |
| Sportsmat Ltd | Wholesale & retail | 2015 |
| Spray-Pro Smart Repairs Limited | Wholesale & retail | 2013 |
| Spraybake Limited | Manufacturing | 2004 |