| S L Crocker Limited | Wholesale & retail | 2007 |
| S O Miller Ltd | Professional & scientific | 2010 |
| S Rigden Services Limited | Construction | 2009 |
| S&G Risk Solutions Limited | Financial services | 2020 |
| SAA Joinery Solutions Limited | Construction | 2026 |
| SAB Group Ltd | Financial services | 2026 |
| SAB Projects Ltd | Construction | 2025 |
| Sabal Health and Pharma Ltd | Wholesale & retail | 2011 |
| Safety Made Simple Limited | Construction | 2023 |
| Safiyaa Central Services Limited | Professional & scientific | 2025 |
| Safiyaa Ipco Limited | Financial services | 2024 |
| Safiyaa Ltd | Wholesale & retail | 2011 |
| Safiyaa S-M-D Limited | Professional & scientific | 2025 |
| SALESAGENT4U Limited | Other services | 2010 |
| Sally Aungier Bookkeeping Limited | Professional & scientific | 2006 |
| Salmo Steak and Seafood Ltd | Hospitality | 2022 |
| SAM West Fitness Limited | Health & social care | 2019 |
| Samlil Services Ltd | Construction | 2014 |
| Sandbank Properties Limited | Real estate | 2018 |
| Sapphire Mortgages Limited | Financial services | 2025 |
| Saraab Limited | Real estate | 2025 |
| Sarah Smyth Limited | Professional & scientific | 2016 |
| Sarjon Developments Limited | Real estate | 2018 |
| Sash Port Training Services Limited | Education | 2021 |
| Sasjem Futures Limited | Financial services | 2024 |
| Saturn Consult Ltd | Professional & scientific | 2021 |
| Saving Energy Property Services Limited | Real estate | 2023 |
| SBS Orthopaedics Limited | Health & social care | 2015 |
| SC Legal Recruitment Limited | Administrative & support | 2024 |
| Scarlett's Rentals Limited | Real estate | 2023 |
| Scates Audio Services Ltd | Information & communication | 2020 |
| Schwartzbard Sutherland Properties Ltd | Real estate | 2021 |
| Scientific Electro Systems Limited | Professional & scientific | 1986 |
| SCL Contract Lifting Ltd | Construction | 2023 |
| Sconzy Limited | Information & communication | 2006 |
| SD & SH Harper LLP | | 2026 |
| SDM Roofing Limited | Construction | 2016 |
| Sea Watch (Management) Limited | Real estate | 1991 |
| Seaside Clearances Limited | Transport & logistics | 2026 |
| Security Systems GRP Rochford Limited | Administrative & support | 2013 |
| Seedbed Admin Services Limited | Administrative & support | 2025 |
| Seeking Supplements Ltd | Other services | 2022 |
| Select Plant Services Ltd | Construction | 2025 |
| Selliseyespy Ltd | Administrative & support | 2025 |
| Serenitybeautie UK Limited | Other services | 2019 |
| Serious Genius Limited | Information & communication | 2023 |
| Services IT Ltd | Information & communication | 2022 |
| Services Mgmt Limited | Real estate | 2026 |
| Seymour Installations Limited | Manufacturing | 2025 |
| SF11 Properties Limited | Real estate | 2019 |
| SGB Windows and Doors Ltd | Construction | 2021 |
| SGL Solutions Limited | Other services | 2024 |
| Shabash Limited | Information & communication | 2003 |
| Shade'N'Shades Ltd | Wholesale & retail | 2024 |
| Shamink Limited | Other services | 1998 |
| Shihaixie Ltd | Wholesale & retail | 2021 |
| Shireoaks Energy Centre Limited | Energy | 2019 |
| Shoebury Garrison Management Company Limited | Households | 2001 |
| Shumi Services Ltd | Health & social care | 2020 |
| Sidujano Limited | Health & social care | 2015 |
| Sigma Signs Ltd | Professional & scientific | 2025 |
| Silent Studios Productions C.I.C. | Information & communication | 2015 |
| Silkstream Limited | Information & communication | 2004 |
| Silver Birch Lodge RTM Company Limited | Administrative & support | 2010 |
| Silver City Property Holdings Limited | Financial services | 2024 |
| Simon Freese Watchmakers Limited | Professional & scientific | 2017 |
| Simon M Limited | Information & communication | 2015 |
| Simplified Consulting Ltd | Information & communication | 2014 |
| Simptrav Ltd | Information & communication | 2025 |
| Simulator Training Ltd | Education | 2022 |
| SIN Gluten Ltd | Wholesale & retail | 2023 |
| Singing Grass Communications Limited | Professional & scientific | 2013 |
| Sinister Castle Pictures Limited | Information & communication | 2021 |
| Sister Dorothy Limited | Health & social care | 2014 |
| SJ Gillies Ltd | Financial services | 2023 |
| SJS Shopfitters Limited | Construction | 2000 |
| SKA Entertainment Ltd | Information & communication | 2026 |
| Skewer House Rochford Limited | Hospitality | 2017 |
| Skinner & Sons Removals & Storage Ltd | Transport & logistics | 2023 |
| Skinner & White Estates Limited | Real estate | 2023 |
| Skinner & White Limited | Professional & scientific | 2024 |
| SMH Property Services Ltd | Construction | 2015 |
| Smithwood Property Holdings Ltd | Real estate | 2026 |
| SMJ Plumbing & Heating Ltd | Construction | 2015 |
| SMK Commercial Vehicles Limited | Wholesale & retail | 2025 |
| SMK Performance Limited | Wholesale & retail | 2019 |
| Snag Tackle Ltd | Wholesale & retail | 2021 |
| SNK Southend CIC | Education | 2022 |
| Snowflower Estates Limited | Real estate | 2017 |
| Social Fusion Media Limited | Information & communication | 2024 |
| Solo Angel Ltd | Professional & scientific | 2018 |
| Solstar I.T. Services Limited | Administrative & support | 2001 |
| Solutions Fire Safety Limited | Wholesale & retail | 2000 |
| Soncino Press Limited(The) | Wholesale & retail | 1929 |
| Sophic Agility Limited | Professional & scientific | 2018 |
| Sophisticake (Canvey Island) Limited | Wholesale & retail | 2013 |
| Sophisticake (Essex) Limited | Wholesale & retail | 2013 |
| South Cambs Physio Ltd | Health & social care | 2026 |
| South East Crane Services Ltd | Manufacturing | 2021 |
| South East Eco Utilities Limited | Construction | 2014 |