| SI Motorsports Ltd | Transport & logistics | 2025 |
| Significant Shine Ltd | Administrative & support | 2018 |
| SIH Sales Ltd | Wholesale & retail | 2025 |
| Silfield Bloodstock Ltd | Agriculture & fishing | 2003 |
| Silva & Silva Limited | Transport & logistics | 2011 |
| Silverark IT Solutions Ltd | Information & communication | 2014 |
| Simmonds Ellis & Co Ltd | Professional & scientific | 2004 |
| Simon Long Removals Limited | Transport & logistics | 1999 |
| Simphonica Ltd | Information & communication | 2022 |
| Sims Flooring Ltd | Construction | 2018 |
| Simstar Concepts Ltd | Information & communication | 2006 |
| Siyabend Limited | Hospitality | 2020 |
| SJS Trading and Supplies Limited | Professional & scientific | 2014 |
| Sjwd Ltd | Professional & scientific | 2024 |
| SK Accountancy & Business Ltd | Professional & scientific | 2013 |
| Skatoskalo International Limited | Manufacturing | 2000 |
| Skatoskalo Limited | Manufacturing | 1992 |
| Skin Memory Limited | Wholesale & retail | 2025 |
| Skyloft Vape Ltd | Wholesale & retail | 2018 |
| Skywing Foods Ltd | Hospitality | 2024 |
| Slinn Flint Ltd | Manufacturing | 2025 |
| Smart ABC East Anglia Ltd | Wholesale & retail | 2017 |
| Smart Garage and MOT Centre Ltd | Wholesale & retail | 2017 |
| Smart IT Control Ltd | Information & communication | 2025 |
| Smart Skin Expert Skin & Laser Clinic Limited | Other services | 2022 |
| Smart Traffic Ltd | Construction | 2024 |
| Smart Under Ltd | Wholesale & retail | 2024 |
| Smartco Ltd | Real estate | 2026 |
| SMF Precision Engineering Ltd | Professional & scientific | 2024 |
| Smudge Films Limited | Information & communication | 2000 |
| SNP Business Ltd | Wholesale & retail | 2026 |
| SNP Retail Ltd | Hospitality | 2025 |
| Snpd Ltd | Real estate | 2015 |
| Soapbox Motorsport Limited | Administrative & support | 2022 |
| Social, Water Access, Network (Swan) CIC | Other services | 2025 |
| SOF Energy Ltd | Construction | 2025 |
| Solo Contract Services Ltd | Construction | 2025 |
| Sopris Business Services Limited | Administrative & support | 1997 |
| Souls Choice Ltd | Wholesale & retail | 2019 |
| Southall Driver Hire Ltd | Transport & logistics | 2023 |
| Southall Group Limited | Financial services | 2024 |
| Space Recruitment Ltd | Administrative & support | 2023 |
| Spaced ENS Publishing Services Limited | Information & communication | 2013 |
| Spacemax Storage Ltd | Construction | 2023 |
| Spark Plug Marketing Limited | Professional & scientific | 2022 |
| Speedbird Promotions Limited | Wholesale & retail | 2008 |
| Speedbird Supplies Ltd | Manufacturing | 2013 |
| Speedy Interiors Ltd | Construction | 2023 |
| Spencer Sales Ltd | Arts & recreation | 2024 |
| Spindrive LGV Ltd | Administrative & support | 2025 |
| Spinney Productions Ltd | Arts & recreation | 2025 |
| Splendour JC Limited | Other services | 2020 |
| Springfield Care Ltd | Health & social care | 2026 |
| SPS A&M Cleaning Services Ltd | Administrative & support | 2024 |
| SQ Food Market Ltd | Wholesale & retail | 2025 |
| SR Survey Support Ltd | Professional & scientific | 2021 |
| SSF 25 Ltd | Hospitality | 2026 |
| ST Cuthbert's Church (Thetford) Cafe Limited | Hospitality | 2019 |
| ST Edmundsbury Homes Ltd | Construction | 2023 |
| ST George's View Management Company Limited | Administrative & support | 1997 |
| ST Leonard's Mead (Residents Management Company) Limited | Households | 2009 |
| ST Mary's Close Heacham Management Company Limited | Households | 2018 |
| ST Neots Property Co Limited | Real estate | 2018 |
| Stag Developments Norfolk Limited | Construction | 2020 |
| Stag Estates Norfolk Ltd | Real estate | 2019 |
| Stannard Builders Limited | Real estate | 2016 |
| Star OK Kebab Ltd | Hospitality | 2017 |
| Star-Jenn Limited | Information & communication | 1995 |
| Starlighteros Technologies Ltd | Information & communication | 2025 |
| Stars N Jars (Thetford) Ltd | Wholesale & retail | 2022 |
| Starworks (Norfolk) Limited | Extraterritorial | 2014 |
| Stedora Ltd | Wholesale & retail | 2024 |
| Stephen Walker Associates Limited | Construction | 2014 |
| Steve Medler Limited | Professional & scientific | 2015 |
| Stirling Service Limited | Construction | 2012 |
| Stirrup & Stone Ltd | Manufacturing | 2021 |
| Stonebridge Green Management Company Limited | Households | 2018 |
| Stop Quick Ltd | Wholesale & retail | 2025 |
| Stove Art Ltd | Construction | 2019 |
| Stratton Haus Limited | Construction | 2025 |
| Strides IT Solutions Ltd | Information & communication | 2022 |
| Strivelink Ltd | Information & communication | 2024 |
| Stuart Marketing Ltd | Information & communication | 2024 |
| Sturgeon International Limited | Professional & scientific | 2021 |
| STV International Limited | Manufacturing | 1994 |
| Stvtech Limited | Construction | 2025 |
| Styella Hair Ltd | Other services | 2004 |
| Su-Bridge Brands Limited | Manufacturing | 2022 |
| Su-Bridge Properties Limited | Real estate | 2019 |
| Suffolk Coins & Collectables Limited | Wholesale & retail | 2026 |
| Sugarbush Consultancy Ltd | Professional & scientific | 2023 |
| Summer Sky Investments Limited | Professional & scientific | 2017 |
| Sun Wind and Power Ltd | Energy | 2007 |
| Sunnah Wear Ltd | Wholesale & retail | 2023 |
| Sunny Hunny Limited | Hospitality | 2026 |
| Sunnyside Construction Training Limited | Education | 2025 |
| Sure Professionals Limited | Administrative & support | 2018 |
| Surfacing UK Limited | Construction | 2024 |
| Sustainable Plastic Solutions Ltd. | Professional & scientific | 2016 |
| Swaffham Glass Limited | Construction | 2002 |