| Soundphonium Limited | Information & communication | 2025 |
| South East Painting Limited | Construction | 2000 |
| South Eastern Warehousing & Distribution Limited | Transport & logistics | 1999 |
| South Essex Care & Health Association Limited | Health & social care | 1994 |
| South Essex Commercial Services Limited | Hospitality | 2003 |
| South Essex Darts Centre Limited | | 1987 |
| South Park Farm Energy Centre Limited | Energy | 2020 |
| South Pole Air Conditioning Ltd | Construction | 2024 |
| South Primrose Hill Management Co. Limited | Administrative & support | 2004 |
| South Wootton Estate Limited | Agriculture & fishing | 2006 |
| Southend Curry House Ltd | Hospitality | 2023 |
| Southend Limited | Real estate | 1998 |
| Southend Masonic Centre Limited | Hospitality | 1956 |
| Southend on Sea Guild of Help and Citizens Advice Bureau | Other services | 2001 |
| Southend Trading Limited | Manufacturing | 1983 |
| Southend Transport Limited | Transport & logistics | 2003 |
| Southend Vineyard | Other services | 1995 |
| Southend-On-Sea Bowls and Social Club Limited | Arts & recreation | 1909 |
| Southern Treats Butchery | | 2006 |
| Southern Tyre Wholesalers Limited | Wholesale & retail | 1992 |
| Southfields Gravel Company Limited | Mining & quarrying | 1964 |
| Southgate Media and Technology Ltd | Information & communication | 2000 |
| Southill Limited | Hospitality | 2017 |
| Southminster Trading Limited | Real estate | 2023 |
| Southwark Place Developments Limited | Real estate | 1971 |
| Southwick Motor Services Ltd | Wholesale & retail | 2023 |
| Sovereign Design Play Systems Limited | Wholesale & retail | 2004 |
| Sovrana Limited | Real estate | 2025 |
| Spa Dental Care Limited | Financial services | 2006 |
| Spa Fish and Chips Ltd | Hospitality | 2018 |
| Spa Sports Limited | Wholesale & retail | 2003 |
| Spacemaker Conversions Limited | | 1992 |
| Spark Gym Clacton on Sea Ltd | Other services | 2024 |
| Spark Tech MEP Limited | Professional & scientific | 2023 |
| Sparkhive Ltd | Wholesale & retail | 2024 |
| Sparkkith Ltd | Information & communication | 2025 |
| Sparktech Electrical Services Ltd | Construction | 2007 |
| Special Accountancy Services Limited | Professional & scientific | 1989 |
| Specialist Floors Limited | Wholesale & retail | 2002 |
| Spectrolite Contracts Limited | Other services | 2006 |
| Spectrum Merchandising Limited | Wholesale & retail | 2007 |
| Spectrum Security Services Limited | Administrative & support | 2001 |
| Speedy Business Services Ltd | Construction | 2000 |
| Speedy Fixings Limited | Administrative & support | 1999 |
| Speedy Invest Limited | Real estate | 2025 |
| Spellweaver Ltd | Wholesale & retail | 2000 |
| Spencer Court (ELM Park) Limited | Real estate | 1994 |
| Spey Control Systems Limited | Manufacturing | 1976 |
| Sphinx Trading Ltd | Manufacturing | 2025 |
| Spice Curry One Ltd | Hospitality | 2024 |
| Spjr Properties Ltd | Real estate | 2024 |
| Sportsignings Ltd | Wholesale & retail | 2021 |
| Spotech Electrical & Security Ltd | Construction | 2025 |
| Spotlime Media Limited | Information & communication | 2022 |
| Spreego Trading Ltd | Wholesale & retail | 2025 |
| Springwell Nursery Limited | Agriculture & fishing | 2003 |
| Sprint Integration Limited | Information & communication | 2001 |
| Sprite Byte Ltd | Information & communication | 1997 |
| SPS Dental Sales Limited | Wholesale & retail | 2003 |
| Spurfreight Limited | | 1989 |
| Squirrel Nutshell Ltd | Wholesale & retail | 2017 |
| Srag Holding Limited | Financial services | 2025 |
| Sreepur Tandoori Ltd | Hospitality | 2025 |
| SRI Tech Limited | Information & communication | 2011 |
| SS Professionals Ltd | Information & communication | 2025 |
| SS Shopping Solutions Ltd | Wholesale & retail | 2025 |
| SS9 Solutions Limited | Professional & scientific | 2007 |
| SSA Business Ltd | Wholesale & retail | 2025 |
| ST Ann's Manufacturing Company Limited | Wholesale & retail | 1908 |
| ST Creation Events Ltd | Arts & recreation | 2024 |
| ST Helens (Brentwood) Wrap Around Care Ltd | Health & social care | 2023 |
| ST James Outfitters Ltd | Professional & scientific | 2002 |
| ST Martins Quarter Management Company Limited | Real estate | 2008 |
| ST Peters Field Green Sward Management Limited | Households | 2007 |
| ST. John's (Billericay) Sports Company Limited | Arts & recreation | 1966 |
| ST. Mary's Park (Dunmow) Management Company Limited | Construction | 2026 |
| ST. Mary's School (Colchester) Limited | Education | 1970 |
| ST. Matthews Christian Spiritualist Church | Other services | 1986 |
| ST. Matthews Christian Spiritualist Church 1999 Limited | Other services | 1999 |
| ST. Monica's Management Company (West) Limited | Real estate | 1974 |
| St.Andrews (Automobiles) Limited | Transport & logistics | 1989 |
| Stablelogic Limited | Administrative & support | 1999 |
| Stace LLP | | 2005 |
| Stace Management Limited | Professional & scientific | 1982 |
| Stafford Young Jones Nominees Limited | Professional & scientific | 1996 |
| Staines & Brights Limited | Wholesale & retail | 2003 |
| Stalanby Engineers Limited | Manufacturing | 1978 |
| Stallion Business Finance UK Ltd | Financial services | 2025 |
| Standard Direct Limited | Real estate | 1996 |
| Stanka Studio Ltd | Wholesale & retail | 2025 |
| Stanley H E Ltd | Education | 2022 |
| Stapleford (USA) Flight Training Organisation Limited | Education | 1992 |
| Staplestock Ltd | Wholesale & retail | 2026 |
| Star Mortgage & Insurance Services Limited | Real estate | 1998 |
| Star Shine Associates Limited | Professional & scientific | 1997 |
| Starks Associates Limited | Information & communication | 2023 |
| Starlight QMD Limited | Professional & scientific | 2006 |
| Starline Developments Limited | | 1985 |
| Starlite (UK) Ltd | Real estate | 2012 |
| Starlite Luggage Limited | Wholesale & retail | 2017 |