| Softwerx Ltd | Information & communication | 1999 |
| Soho Editor Limited | Information & communication | 2003 |
| Solar RTM Company Limited | Households | 2017 |
| SOLUTIONS95 Ltd | Information & communication | 2013 |
| Something Green Ltd | Construction | 2019 |
| Sourcing Resourcing Ltd | Administrative & support | 2011 |
| South East Plant Services Ltd | Other services | 2022 |
| South Essex Building Preservation Trust | Health & social care | 1978 |
| South Essex Electrical Limited | Construction | 2001 |
| South Essex Interiors & Exteriors Ltd | Construction | 2022 |
| Southash House Limited | Real estate | 2025 |
| Southern Building, Maintenance & Environmental Services Ltd | Construction | 2019 |
| Southern Counties Property Co Ltd | Real estate | 2020 |
| Southfields Ventures Ltd | Real estate | 2018 |
| Sowerby Keene Limited | Construction | 2014 |
| SP Construction Essex Ltd | Construction | 2023 |
| SP Residential Ltd | Real estate | 2004 |
| Sparks Electrical Services Ltd | Energy | 2018 |
| Sparoh Ltd | Administrative & support | 2021 |
| Spartan Demolition Limited | Construction | 2022 |
| Speak the Speech Limited | Administrative & support | 2005 |
| Speakeasybar Ltd | Hospitality | 2007 |
| SPG P1 Ltd | Real estate | 2025 |
| Spice HUT SS6 Ltd | Hospitality | 2016 |
| SPM Essex Limited | Households | 2022 |
| Spot Storage Ltd | Transport & logistics | 2025 |
| Sprg Electrical Ltd | Construction | 2019 |
| SPS Mortgages Ltd | Administrative & support | 2016 |
| Spuddies & Sweet Cravings Limited | Hospitality | 2025 |
| SQT Limited | Wholesale & retail | 2012 |
| Square Key Developments Ltd | Construction | 2025 |
| Square-Biz Ltd | Wholesale & retail | 2021 |
| SRD Furniture Ltd | Wholesale & retail | 2025 |
| SS Airport Travel Limited | Transport & logistics | 2023 |
| SS22 Services Ltd | Other services | 2022 |
| SSS Consultancy Services Ltd | Professional & scientific | 2023 |
| ST George Sports Ltd | Wholesale & retail | 2015 |
| ST Helens RTM Company Limited | Real estate | 2010 |
| ST Johns Estate Management (Rayleigh) Limited | Professional & scientific | 2020 |
| ST Raphael's Place Brentwood (Freehold) Limited | Households | 2011 |
| Stack House Gym Ltd | Arts & recreation | 2017 |
| Stadium Way Management Limited | Real estate | 2018 |
| Staffordshire Holdings Limited | Hospitality | 2016 |
| Stanway Partnership Ltd | Real estate | 2017 |
| Star Class Spares Ltd | Wholesale & retail | 2021 |
| Stark Capital Limited | Financial services | 2024 |
| Stateside Trucks Limited | Wholesale & retail | 2012 |
| Station Garage (Rayleigh) Limited | Wholesale & retail | 2001 |
| Steeltronics Limited | Administrative & support | 2005 |
| Steggles & Co Limited | Financial services | 2004 |
| STEP2INNOVATE Ltd | Wholesale & retail | 2018 |
| Stephen Cornwell Ltd | Manufacturing | 2019 |
| Steps Estate Agents Limited | Real estate | 2003 |
| Steps Property Services Limited | Real estate | 2014 |
| Sterling Install Limited | Professional & scientific | 2026 |
| Steve Bennett Consulting Ltd | Professional & scientific | 2017 |
| Stewarts Property Group Ltd | Financial services | 2025 |
| Stewarts Roofing Services Ltd | Construction | 2023 |
| Stickerman Studios Ltd | Professional & scientific | 2019 |
| Stitch Town Limited | Wholesale & retail | 2018 |
| Stone Cast Solutions Ltd | Water & waste | 2020 |
| Stone Properties Group Limited | Real estate | 2018 |
| Storvite Flooring Ltd | Construction | 2005 |
| Storvite Group Ltd | Administrative & support | 2025 |
| Storvite Services Ltd | Water & waste | 2025 |
| Stour Hospitality Ltd | Wholesale & retail | 2020 |
| Stoveweld Ltd | Construction | 2009 |
| Stradcom Ltd | Information & communication | 2022 |
| Strang Aviation Ltd | Manufacturing | 2018 |
| Stranten Limited | Administrative & support | 2019 |
| Strong World Limited | Administrative & support | 2021 |
| Stuart Asher Services Ltd | Professional & scientific | 2025 |
| Stuart Medcraft Consultancy Limited | Professional & scientific | 2020 |
| Stuarts of Rayleigh Ltd | Wholesale & retail | 2014 |
| Studio 6 Plus 1 Ltd | Information & communication | 2024 |
| Studio Alma Limited | Arts & recreation | 2025 |
| Studio NOA Limited | Professional & scientific | 2016 |
| STUDIO80SIX Ltd | Professional & scientific | 2016 |
| Sturge East Residential Ltd | Real estate | 2018 |
| Subvision Holdings Ltd | Administrative & support | 2016 |
| Subvision Limited | Administrative & support | 2016 |
| Subvision Surveying Group Ltd | Administrative & support | 2016 |
| Subvision Surveying Ltd | Administrative & support | 2016 |
| Subvision Surveying Services Ltd | Extraterritorial | 2015 |
| Subvision Surveys Group Ltd | Administrative & support | 2016 |
| Subvision Surveys Ltd | Professional & scientific | 2013 |
| Subvision Surveys Solutions Ltd | Extraterritorial | 2015 |
| Subvision UAV Ltd | Administrative & support | 2016 |
| Sumro Plumbing & Heating Limited | Construction | 2022 |
| SUN2SUN Ltd | Extraterritorial | 2025 |
| Sunjade Limited | Transport & logistics | 1995 |
| Sunshine Scooters Limited | Arts & recreation | 2019 |
| Sunshine Yellow MEP Limited | Construction | 2024 |
| Supercar Concierge Ltd | Other services | 2013 |
| Supplies 2 Office Ltd | Administrative & support | 2007 |
| Supporting Carers and Families Together | Health & social care | 2009 |
| Supreme 3D Print Ltd | Manufacturing | 2026 |
| Supreme Coatings Limited | Manufacturing | 2022 |
| Supreme Enterprises Limited | Real estate | 1994 |
| Sureminded Limited | Health & social care | 2010 |