| Stowmarket Arts CIC | Education | 2022 |
| Stowmarket B Ltd | Wholesale & retail | 2023 |
| Stowmarket Care Centre 2 Limited | Health & social care | 2019 |
| Stowmarket Chamber of Commerce Ltd. | Other services | 2014 |
| Stowmarket Estates Limited | Administrative & support | 2015 |
| Stowmarket Glass Co. Limited | Construction | 1990 |
| Stowmarket Golf Shop Limited | Arts & recreation | 2014 |
| Stowmarket Luggage Ltd | Wholesale & retail | 2023 |
| Stowmarket Station Ltd | Administrative & support | 2020 |
| STP (Anglia) Limited | Construction | 2021 |
| Strada Services Limited | Administrative & support | 2016 |
| Stradaptive Ltd | Information & communication | 2026 |
| Straightline Transport Consultancy Limited | Transport & logistics | 2025 |
| Strata Stones Limited | Wholesale & retail | 2004 |
| Stratagem 365 Ltd | Wholesale & retail | 2023 |
| Strategic Continuity Limited | Professional & scientific | 2007 |
| Strategic Energy Limited | Professional & scientific | 2019 |
| Strategic Planning (Essex) Ltd | Professional & scientific | 2016 |
| Strategix Comms Ltd | Professional & scientific | 2024 |
| Stratford 47 Limited | Arts & recreation | 2002 |
| Stratis Asset Protection Limited | Construction | 2022 |
| Stratis Fire & Security Limited | Public administration | 2023 |
| Stratus Technology Solutions Limited | Information & communication | 2025 |
| Straw Resource UK Engineering Limited | Manufacturing | 2023 |
| Strawberry Heaven Limited | Agriculture & fishing | 2013 |
| Strawberry Lemon Digital Limited | Professional & scientific | 2022 |
| Strawstone Limited | Construction | 1984 |
| Street Farm Gardens Management Limited | Real estate | 2006 |
| Streetyard Ltd | Information & communication | 2012 |
| Stride Sports Limited | Manufacturing | 2025 |
| Strident Group Limited | Information & communication | 2001 |
| Strident Limited | Information & communication | 2003 |
| Stridex Academy Limited | Education | 2025 |
| Strike a Pose Hire Ltd | Administrative & support | 2020 |
| Strokes Swimschool Limited | Education | 2018 |
| Strong Coaching Ltd | Other services | 2021 |
| Strong Consultancy Limited | Other services | 2026 |
| Stronghold Trading Ltd | Transport & logistics | 2018 |
| Stroud Associates Ltd | Professional & scientific | 2000 |
| Strowger Ltd | Hospitality | 2025 |
| Struan Walker Sports and Media Limited | Professional & scientific | 2024 |
| Structelio Goods Ltd | Wholesale & retail | 2026 |
| Structure Asset Holdings Ltd | Administrative & support | 2025 |
| Strydes of Ipswich Ltd | Wholesale & retail | 2026 |
| STS Haulage Ltd | Transport & logistics | 2012 |
| Stuart James Digital Marketing LP | | 2019 |
| Stuart Morris (Holdings) Ltd | Financial services | 2023 |
| Stuart Morris Design Ltd | Arts & recreation | 2023 |
| Stuart Rodd Limited | Professional & scientific | 2012 |
| Stubborn Theory Ltd | Information & communication | 2024 |
| Studio 47 Hair and Beauty Ltd | Other services | 2023 |
| Studio D Limited | Real estate | 2009 |
| Studio DP Ltd | Professional & scientific | 2024 |
| Studio Onefourfour Limited | Other services | 2024 |
| Study Wise UK Ltd | Education | 2012 |
| Studywise Consultants Ltd | Wholesale & retail | 2024 |
| Sturgeon Builders Limited | Construction | 2011 |
| Stutton Community Shop CIC | Wholesale & retail | 2007 |
| Stutton Investments | Financial services | 2019 |
| Stutton Real Estate Limited | Real estate | 2025 |
| STV Facilities Group Ltd | Information & communication | 2026 |
| Stylentra Identity Flow Ltd | Information & communication | 2026 |
| Stylers Ipswich Limited | Other services | 2015 |
| SU & ME Ltd | Hospitality | 2025 |
| SU Impressions Limited | Professional & scientific | 2015 |
| Subconscious Therapy Ltd | Health & social care | 2024 |
| Subeo (UK) Limited | Professional & scientific | 2003 |
| Subhan Engineering Limited | Manufacturing | 2014 |
| Subhan Properties Limited | Real estate | 2014 |
| Submelya Enquiry Flow Ltd | Information & communication | 2026 |
| Submerge Clothing Ltd. | Manufacturing | 2020 |
| Submiora Format Alignment Ltd | Information & communication | 2026 |
| Success Avenue Ltd | Wholesale & retail | 2024 |
| Success IS NOT Limited | Wholesale & retail | 2025 |
| Success MINDSET365 Ltd | Information & communication | 2021 |
| Success Synergies Ltd | Professional & scientific | 2024 |
| Suckling Electrical Contractors Limited | Construction | 2002 |
| Sudbury T C Limited | Manufacturing | 2003 |
| Sudely Street Ltd | Real estate | 2024 |
| Suffolk & Essex Snagging Limited | Construction | 2022 |
| Suffolk & Norfolk Cladding Ltd | Wholesale & retail | 2009 |
| Suffolk 4X4 Limited | Wholesale & retail | 2008 |
| Suffolk Academy of Dance & Performing Arts Ltd | Education | 2025 |
| Suffolk Advanced Glazing Limited | Construction | 2022 |
| Suffolk Agricultural Association | Education | 1983 |
| Suffolk Apiaries Ltd | Agriculture & fishing | 2024 |
| Suffolk Asbestos Solutions Limited | Construction | 2022 |
| Suffolk Asset Management Ltd | Professional & scientific | 2004 |
| Suffolk Bar and Club Ltd | Hospitality | 2023 |
| Suffolk Beet Company Ltd | Agriculture & fishing | 2019 |
| Suffolk Best Kebab Ltd | Hospitality | 2025 |
| Suffolk Books Limited | Professional & scientific | 2023 |
| Suffolk Building and Construction Services Ltd | Construction | 2018 |
| Suffolk Building Control Limited | Professional & scientific | 1993 |
| Suffolk Building Group Limited | Construction | 2016 |
| Suffolk Business Agency Limited | Administrative & support | 2001 |
| Suffolk Business Consultancy Ltd | Professional & scientific | 2019 |
| Suffolk Business Park Management Company (Zone 1) Limited | Households | 2019 |
| Suffolk Business Park Management Company (Zone 2) Limited | Households | 2025 |
| Suffolk Busy Bees Ltd | Professional & scientific | 2025 |