| South East Fabrication Ltd | Manufacturing | 2006 |
| South Shelter Limited | Information & communication | 2025 |
| Southquay Enterprises Limited | Real estate | 2005 |
| Sovereign Turf (Wholesale) Ltd | Wholesale & retail | 2009 |
| Sovereign Turf Limited | Agriculture & fishing | 1993 |
| Sparrows Nest (Holdings) Limited | Extraterritorial | 2013 |
| Sparrows Nest Properties Limited | Real estate | 2005 |
| Speak Office Interiors Ltd | Wholesale & retail | 2024 |
| Spectrum Screen Inks Limited | Manufacturing | 2010 |
| Speed Health Solutions Limited | Administrative & support | 2023 |
| Spencer WIX Stone Mason Ltd | Other services | 2012 |
| Sphere 10 Ltd | Arts & recreation | 2019 |
| Sports Class Ltd. | Manufacturing | 1996 |
| Spring Tide Fish Limited | Other services | 2003 |
| Springle Pubs Ltd | Hospitality | 2018 |
| Springwater Capital Limited | Financial services | 2023 |
| Springwater Limited | Households | 1978 |
| Springwater Property Limited | Real estate | 2009 |
| Squashed Grapes Limited | Extraterritorial | 2000 |
| Squirrell Development Group Ltd | Construction | 2025 |
| SRH Allen Ltd | Wholesale & retail | 2021 |
| SSE Homes Ltd | Construction | 2018 |
| ST Audrys Golf Club Limited | Hospitality | 2021 |
| ST Industrial Access Ltd | Construction | 2021 |
| ST James's Property Company Limited | Construction | 2002 |
| ST Peters Close Management Company Ltd | Real estate | 2021 |
| ST. Gusto's Limited | Manufacturing | 2004 |
| STA Technical Ltd | Wholesale & retail | 2015 |
| Stakka Change Consultancy Ltd | Professional & scientific | 2023 |
| Standout Digital Solutions Limited | Information & communication | 2020 |
| Star & Plus Handyman Service Ltd | Construction | 2022 |
| Star Tandoori Indian Take-Away & Restaurant Ltd | Hospitality | 2019 |
| Static Caravan Finder Limited | Information & communication | 2000 |
| Staverton Projects Limited | Real estate | 2001 |
| Steadingscakeandcoffee Ltd | Hospitality | 2025 |
| Stealth Brands Limited | Wholesale & retail | 2010 |
| Stearman Ltd | Real estate | 1997 |
| Steel Consult Limited | Other services | 2023 |
| Steleo Ltd | Information & communication | 2025 |
| Stephen Caulfield & SON Limited | Wholesale & retail | 2001 |
| Stephen Fletcher Associates Ltd | Administrative & support | 2010 |
| Stephenson Bros Ltd | Agriculture & fishing | 2003 |
| Steve Cooper Consulting Ltd | Professional & scientific | 2025 |
| Steve Elvin Plumbing & Heating Limited | Construction | 2014 |
| Steventon Investments Ltd | Financial services | 2024 |
| Stevoconsult Ltd | Professional & scientific | 2020 |
| Steward Farms Ltd | Agriculture & fishing | 2025 |
| Stitchworks Limited | Other services | 2022 |
| Stokes Executive Travel Ltd | Transport & logistics | 2025 |
| Stokes Sauces Ltd | Manufacturing | 2004 |
| Store Secure Suffolk Ltd | Transport & logistics | 2016 |
| Storm Business Consulting Limited | Professional & scientific | 2010 |
| Storm Robotics Limited | Information & communication | 2009 |
| Story Vigar & Partners Limited | Professional & scientific | 2024 |
| Stowe Bespoke Joinery Ltd | Manufacturing | 2023 |
| Stowe Building Contractors Limited | Construction | 2010 |
| Stowe Hyam Scaffolding Limited | Construction | 2018 |
| Street Farm Barns Management Company Limited | Real estate | 2014 |
| Strong Marketing Ltd | Wholesale & retail | 2009 |
| Stuart Beer & Co Limited | Wholesale & retail | 2005 |
| Stuart Farley Transport Limited | Transport & logistics | 2017 |
| Stubborn Mule Travel Ltd | Administrative & support | 2011 |
| Studio Callaghan Limited | Professional & scientific | 1998 |
| Studio Collis Ltd | Information & communication | 2015 |
| Studio Markot Ltd | Information & communication | 2020 |
| Studio Mesh Digital Ltd | Information & communication | 2024 |
| Subcity Pumps Limited | Administrative & support | 2023 |
| Sudbourne Management Company Limited | Households | 2018 |
| Sudbourne Park Residents Association Limited | Other services | 1984 |
| Sudbourne Shoot Syndicate Limited | Extraterritorial | 2018 |
| Suffolk Classic Services Ltd | Wholesale & retail | 2020 |
| Suffolk Coastal CIC | Professional & scientific | 2014 |
| Suffolk Coastal Farmers Limited | Extraterritorial | 2012 |
| Suffolk Coastal Properties Ltd | Households | 2024 |
| Suffolk Coastal Trading Ltd | Wholesale & retail | 2023 |
| Suffolk Content Creators Limited | Professional & scientific | 2023 |
| Suffolk Farm Machinery Ltd | Wholesale & retail | 2015 |
| Suffolk Fwag Limited | Professional & scientific | 2011 |
| Suffolk Heating (Ipswich) Limited | Construction | 2009 |
| Suffolk Heating Ltd | Construction | 2025 |
| Suffolk Heritage Lime Limited | Construction | 2024 |
| Suffolk Horse Society(The) | Agriculture & fishing | 1891 |
| Suffolk Horse Transport Ltd | Transport & logistics | 2021 |
| Suffolk Lotus Limited | Wholesale & retail | 2015 |
| Suffolk Millwright Ltd | Construction | 2025 |
| Suffolk MOT and Service Centre Ltd | Wholesale & retail | 2024 |
| Suffolk Open Air Cinema Limited | Information & communication | 2024 |
| Suffolk Pickleball Company Ltd | Education | 2026 |
| Suffolk Produce Limited | Agriculture & fishing | 2004 |
| Suffolk Property Developments Ltd | Construction | 2025 |
| Suffolk Punch Construction Ltd | Construction | 2005 |
| Suffolk Radiators Ltd | Wholesale & retail | 2023 |
| Suffolk Repair Shed Ltd | Other services | 2022 |
| Suffolk Retreats Ltd | Professional & scientific | 2021 |
| Suffolk River Trips Limited | Transport & logistics | 2020 |
| Suffolk Saucery Limited | Manufacturing | 2004 |
| Suffolk Seed Stores,Limited(The) | Construction | 1919 |
| Suffolk Self Storage Limited | Real estate | 2014 |
| Suffolk Stove Enamellers Limited | Manufacturing | 2015 |
| Suffolk Straw Limited | Agriculture & fishing | 2020 |