| Sonner Plant & Agricultural Contractors Limited | Construction | 1975 |
| Sora Holdings Limited | Financial services | 2025 |
| Sound Decision Consulting Ltd | Professional & scientific | 2014 |
| Soundbyte Solutions (UK) Ltd | Manufacturing | 1998 |
| Soundsabre Limited | Extraterritorial | 2014 |
| South Coast Auto Solutions Limited | Wholesale & retail | 2014 |
| South Coast Car &Commercial Valeting Service Ltd | Administrative & support | 2025 |
| South Coast Hot Tubs Ltd | Administrative & support | 2023 |
| South Drive Cattistock Limited | Real estate | 2024 |
| South Drive House Cattistock Management Company Limited | Households | 1998 |
| South West Dorset Multicultural Network | Education | 2011 |
| South West IT Ltd | Information & communication | 2016 |
| South Western Scaffolding Limited | Construction | 1977 |
| Southbalt Consulting Limited | Professional & scientific | 2024 |
| Southby Limited | Administrative & support | 2012 |
| Southby Productions LLP | | 2013 |
| Southcoast Powerhouse Ltd | Arts & recreation | 2015 |
| Southern Electronic Services Limited | Wholesale & retail | 1986 |
| Southern Manufacturing Electronics Limited | Manufacturing | 2015 |
| Southern Medical Gases Limited | Construction | 2013 |
| Southern Motocross Club-Smx Limited | Arts & recreation | 2018 |
| Southern Renewables Ltd | Construction | 2022 |
| Southern Reservoir Engineering Limited | Mining & quarrying | 1996 |
| Southern Steel Detailing Ltd | Professional & scientific | 2025 |
| Southover Events Limited | Hospitality | 2017 |
| Southover Holidays Ltd | Hospitality | 2025 |
| Southwest Taxi Contracts Ltd | Other services | 2017 |
| Southwest Woodburners Limited | Construction | 2024 |
| Southwood Secure Storage Ltd | Other services | 2020 |
| Souvlaki and More Ltd | Hospitality | 2020 |
| Sovereign House Property Management Limited | Households | 2017 |
| SP Group of Overseas Education and Staffing Solution Ltd | Administrative & support | 2022 |
| Spaceflight Academy Limited | Transport & logistics | 2007 |
| Spansix Ltd | Extraterritorial | 2012 |
| Spark Energy Consultants Ltd | Professional & scientific | 2023 |
| Sparktex Ltd | Construction | 2025 |
| Sparrowbush Livery Ltd | Agriculture & fishing | 2025 |
| Sparrowbush Properties Limited | Agriculture & fishing | 2008 |
| Spase Ltd. | Professional & scientific | 2015 |
| Spea Properties Limited | Real estate | 2024 |
| Specialist Electro Technical Services Limited | Construction | 2006 |
| Specialist Video Services Limited | Information & communication | 2003 |
| Speech to Text Limited | Information & communication | 2014 |
| Spendhire Limited | Construction | 1997 |
| Sphere 24 Ltd | Administrative & support | 2010 |
| Sphere 24 Services Limited | Administrative & support | 2017 |
| Spirare Limited | Professional & scientific | 2012 |
| Spires Landscaping Limited | Administrative & support | 2018 |
| Sportarm at Wlss Ltd | Wholesale & retail | 2019 |
| Sportarm Limited | Wholesale & retail | 2000 |
| Sportfishing Charters Limited | Transport & logistics | 2024 |
| Sports Medical Consultants Ltd | Health & social care | 2023 |
| Sports Rights Consulting Group Ltd | Professional & scientific | 2018 |
| Spotzeroeu Limited | Manufacturing | 2022 |
| Springwood Farms Limited | Agriculture & fishing | 2004 |
| Sprint Signs Dorchester Ltd | Manufacturing | 2019 |
| SPRINT3D Ltd | Manufacturing | 2022 |
| SPS Energy Systems Ltd | Wholesale & retail | 2023 |
| Square Newsagent Limited | Wholesale & retail | 2012 |
| SRB Connect Limited | Professional & scientific | 2023 |
| SRS Dorset Ltd | Construction | 2025 |
| Ssae Holdings Ltd | Real estate | 2026 |
| SSC Leisure Group Ltd | Transport & logistics | 2020 |
| SSF Site Works Limited | Construction | 2015 |
| SSF Small Works Ltd | Manufacturing | 2013 |
| ST Hildas 52 Victoria Grove Bridport Management Limited | Households | 2004 |
| ST John Way Management Limited | Administrative & support | 2010 |
| ST Mary Elite Estates (Smee) Ltd | Real estate | 2025 |
| ST Mary Stratton Ltd | Households | 2018 |
| ST. Catherines Flint Products Limited | Mining & quarrying | 2002 |
| ST. Cecilia Care Dorset Limited | Health & social care | 2010 |
| ST. Christopher Developments Ltd | Construction | 2015 |
| ST. John's Court Residents Association Limited | Households | 1983 |
| ST. John's Place Management Limited | Households | 2002 |
| ST. Lucia EYE Services Ltd | Health & social care | 2025 |
| Stackd Productions Ltd | Manufacturing | 2023 |
| Stacks (Dorset) Limited | Administrative & support | 2017 |
| Staffordshire Urology Clinic LLP | | 2011 |
| Stag Build (Dorset) Ltd | Construction | 2020 |
| Stag Domestic & Commercial Fencing Ltd | Construction | 2024 |
| Stag Sheds & Garden Building Ltd | Administrative & support | 2024 |
| Stand: Save the Area North of Dorchester | Other services | 2021 |
| Stanley Street Management Company Limited | Households | 2007 |
| Stanton Court (Greenhill) Management Company Limited | Households | 2001 |
| Starmaker Personal Security Systems Ltd | Administrative & support | 2016 |
| Starmaker Records Limited | Arts & recreation | 2001 |
| Starry Clover Ltd | Other services | 2024 |
| Startline Stories Limited | Arts & recreation | 2026 |
| Startpoint Property Limited | Real estate | 2015 |
| Steeple Holdings Limited | Financial services | 2018 |
| Steigens UK Ltd | Extraterritorial | 2013 |
| Stelar London Limited | Professional & scientific | 2017 |
| Step Ahead Technology Limited | Information & communication | 1995 |
| Stephen Packer Golf Limited | Arts & recreation | 2011 |
| Stephen Sheldon Limited | Professional & scientific | 2002 |
| Sterba DE Vescy Communication Management Ltd. | Administrative & support | 1996 |
| Steve Bane Fabrics Limited | Wholesale & retail | 2002 |
| Steve Bendon Limited | Professional & scientific | 2011 |
| Steve Dando Ltd | Construction | 2014 |
| Steve Green Property Maintenance Ltd | Construction | 2021 |