| SDL (Rochford) Ltd | Construction | 2014 |
| SDM Ductwork Limited | Construction | 2020 |
| SDS Fencing Company Limited | Construction | 2007 |
| Sds-Digital-Services Ltd | Information & communication | 2026 |
| Seacrest Group Limited | Hospitality | 2017 |
| Seaend Limited | Other services | 2017 |
| Seafront Business Company Ltd | Hospitality | 2025 |
| Sealand Services Ltd | Wholesale & retail | 2018 |
| Sean Thomas Ltd | Construction | 2025 |
| Seao Limited | Professional & scientific | 2026 |
| Seaside Movers Ltd | Transport & logistics | 2023 |
| Seasider Skate School Ltd | Education | 2022 |
| Seasons in Thyme Catering Limited | Other services | 2015 |
| Seaview Care Ltd | Health & social care | 2019 |
| Seaview Property Group Ltd | Real estate | 2017 |
| Seaway Southend Limited | Real estate | 1992 |
| Seawing Flying Club Limited | Other services | 1979 |
| Sech Limited | Construction | 2006 |
| Second First Love Ltd | Information & communication | 2022 |
| Second Management Consultancy Ltd | Professional & scientific | 2023 |
| Secret Greenhouse Ltd | Agriculture & fishing | 2026 |
| Securasoft Limited | Information & communication | 2025 |
| Secure Measures Marine Limited | Water & waste | 2013 |
| Securedigital Limited | Information & communication | 2025 |
| Sedna Professional Ltd | Administrative & support | 2019 |
| Seed Secured Ltd | Information & communication | 2021 |
| Seed&Bloom Limited | Administrative & support | 2020 |
| Sejal Patel Limited | Health & social care | 2026 |
| Selby's Catering Ltd | Hospitality | 2024 |
| Select Supported Care Limited | Health & social care | 2016 |
| Self Storage Solutions Ltd | Real estate | 2020 |
| Sell Fish Southend Ltd | Hospitality | 2025 |
| Semper Anticus Limited | Information & communication | 2014 |
| Send More Media Limited | Other services | 2025 |
| Senkoun Healthcare Wakering Ltd | Administrative & support | 2023 |
| Sensas Distribution UK Ltd | Wholesale & retail | 2020 |
| Sentra Security Protection Ltd | Administrative & support | 2024 |
| SEO Paradise Ltd | Professional & scientific | 2025 |
| Sepry Limited | Construction | 2026 |
| Serene Effect Ltd | Professional & scientific | 2024 |
| Serenity Haven Limited | Health & social care | 2026 |
| Sergey Ksaveryev Limited | Financial services | 2023 |
| Service Garage MOT & Repair Centre Limited | Wholesale & retail | 2000 |
| Service LED Approach Ltd | Administrative & support | 2017 |
| SES Electrical Contractors Ltd | Construction | 2005 |
| Seven Day Care (Essex) Limited | Health & social care | 2019 |
| Seven Day Healthcare Training Ltd | Education | 2024 |
| Seven Seas Investments Ltd | Real estate | 2020 |
| Seven VA Support Ltd | Administrative & support | 2022 |
| SG Assured Limited | Professional & scientific | 2023 |
| SGA Realisations (2026) Ltd | Administrative & support | 2018 |
| SGE Group Ltd | Professional & scientific | 2020 |
| SGT Building Services Limited | Construction | 1983 |
| SHA Life Wrestling Ltd | Arts & recreation | 2026 |
| Shadow Estates Ltd | Real estate | 2014 |
| Shadow Property 1 Ltd | Households | 2020 |
| Shahid Ventures Ltd | Wholesale & retail | 2025 |
| Shala Holdings Limited | Real estate | 2025 |
| Shamrock Leones Ltd | Real estate | 2005 |
| Shan 2020 Limited | Hospitality | 2020 |
| Shanahan Electrical Limited | Construction | 2015 |
| Shangami Ltd | Manufacturing | 2026 |
| Shannon Building Solutions Limited | Construction | 2012 |
| Shannon Lansdown Limited | Health & social care | 2007 |
| Sharkey Structural Design Ltd | Professional & scientific | 2013 |
| Sharp Aerospace Limited | Wholesale & retail | 2004 |
| Shattered Stone Forge Limited | Administrative & support | 2026 |
| Shayon Ltd | Wholesale & retail | 2015 |
| Shazmart UK Ltd | Wholesale & retail | 2025 |
| Shears Court (West Mersea) Management Co. Limited | Households | 1979 |
| Shelly Care Services Ltd | Health & social care | 2020 |
| Sherpur Enterprise Ltd | Hospitality | 2024 |
| Sherwin Homes Ltd | Real estate | 2018 |
| Shift Workers Fitness Club Ltd | Wholesale & retail | 2025 |
| Shinecastle Limited | Professional & scientific | 1981 |
| Shinra Corporation Limited | Administrative & support | 2017 |
| Shiny Happy Studios 1 Ltd | Information & communication | 2016 |
| Shipping and Commercial Legal Costs Ltd | Professional & scientific | 2022 |
| Shiramed Limited | Administrative & support | 2026 |
| Shirleys Tyres Limited | Wholesale & retail | 1993 |
| Shisha World Market Ltd | Wholesale & retail | 2026 |
| Shoebury Coastal Community Interest Company | Arts & recreation | 2016 |
| Shoebury Confectionery Limited | Manufacturing | 1991 |
| Shoebury Plumbing & Heating Ltd | Construction | 2013 |
| Shoeburyness Property Management Company Limited | Households | 2011 |
| Shoeburyness Sushi Ltd | Hospitality | 2020 |
| Shols Investment Ltd | Real estate | 2015 |
| Shoreditch Design Ltd | Wholesale & retail | 2013 |
| Shoreline Leisure Limited | Arts & recreation | 2026 |
| Shoreline M&E Ltd | Professional & scientific | 2022 |
| Shoreline Securities Limited | Real estate | 2012 |
| Show First Digital Ltd | Professional & scientific | 2026 |
| Shri Communications Limited | Information & communication | 2010 |
| Shri Enterprises Limited | Wholesale & retail | 2010 |
| Shsc Handrails Limited | Manufacturing | 2012 |
| Shuka Studio Limited | Information & communication | 2021 |
| Shun's Restaurant Ltd | Hospitality | 2024 |
| Sicca Holdings Limited | Real estate | 2022 |
| Sienna Rose Holdings Limited | Real estate | 2025 |
| Sierra Auto Group Ltd | Wholesale & retail | 2024 |