| Sameb Consulting Ltd | Construction | 2025 |
| Sandy Lane Partners Ltd | Professional & scientific | 2021 |
| Sandy Lodge Tenants' Association Limited | Households | 1984 |
| SAO Learning Ltd | Other services | 2017 |
| Sapphire Blue Energy LLP | | 2022 |
| Sapphire Events & Consultancy Limited | Administrative & support | 2026 |
| Sapphire Insight Limited | Administrative & support | 2011 |
| Sarah&David Ltd | Manufacturing | 2020 |
| Sarah's Pampered Poochies Limited | Other services | 2016 |
| Sareez London Ltd | Wholesale & retail | 2024 |
| Saxon Chauffeur Services Ltd | Transport & logistics | 2018 |
| Saxon Court (South Benfleet) Management Company Limited | Households | 1989 |
| Saxon Court (South Benfleet) RTM Company Limited | Households | 2013 |
| SAY Safety Limited | Professional & scientific | 2023 |
| SBR Supplies Ltd | Wholesale & retail | 2024 |
| Scaff AID Ltd | Information & communication | 2025 |
| Scale UP Ltd | Professional & scientific | 2018 |
| Schools for Every Child | Education | 2013 |
| Schwarz Logistics Limited | Health & social care | 2013 |
| Scjg Consultants Limited | Professional & scientific | 2022 |
| SCL Rail Limited | Construction | 2020 |
| Scopes Asbestos Analysis Services Limited | Professional & scientific | 2004 |
| Scorpion Utility Services Ltd | Construction | 2025 |
| Scotts of Rayleigh Ltd | Hospitality | 2024 |
| Screedafloor Limited | Construction | 2011 |
| Scrubbydo Services Ltd | Administrative & support | 2025 |
| SDA Property Rentals Limited | Real estate | 2020 |
| Seduce Social Ltd | Other services | 2025 |
| Seeco (Holdings) Limited | Financial services | 2002 |
| Seeco (Single PLY) Limited | Construction | 1993 |
| Segadi Limited | Other services | 2019 |
| Segadi Marketplace Ltd | Wholesale & retail | 2021 |
| Select Office Services Limited | Administrative & support | 1998 |
| Select Property Options Limited | Financial services | 2012 |
| Self Storage Property Holdings Ltd | Real estate | 2025 |
| Selkirk Property Investments Ltd | Real estate | 2017 |
| Sellwood Planning Limited | Administrative & support | 2007 |
| Serin Creative Limited | Other services | 2016 |
| Serloe Ltd | Transport & logistics | 2020 |
| Service Radar Limited | Professional & scientific | 2012 |
| Setom Limited | Financial services | 2011 |
| Setom Management Limited | Real estate | 2020 |
| Setom Property Limited | Real estate | 2017 |
| Sevenseat Printing Limited | Administrative & support | 2016 |
| SEVENTY6 Building Services Ltd | Construction | 2019 |
| Severin House Ltd | Real estate | 2021 |
| SG Padel Group Ltd | Administrative & support | 2019 |
| SGT Carpentry and Building Ltd | Construction | 2015 |
| Shared Energy Ltd | Other services | 2021 |
| Sharon Griffiths Ltd | Other services | 2021 |
| Sharp Leisure Consultancy and Bar Services Ltd | Hospitality | 2018 |
| Shining Stars Education Ltd | Education | 2025 |
| Shivelight Ltd | Arts & recreation | 2025 |
| Shore Scaffolding Holdings Limited | Financial services | 2017 |
| Shore Taylor Holdings Limited | Financial services | 2025 |
| Shorehouse Design Ltd | Construction | 2009 |
| Show Film First (USA) Ltd | Arts & recreation | 2019 |
| Showtime Solutions Limited | Arts & recreation | 2025 |
| Shrubbro Installations Limited | Construction | 2014 |
| Shuchan Limited | Professional & scientific | 2022 |
| Signal Pharma Experts (UK) Limited | Professional & scientific | 2023 |
| Signal Research Ltd | Manufacturing | 2023 |
| Silika Limited | Construction | 2012 |
| Simon Britten Dentures Limited | Manufacturing | 2015 |
| Simon Ellis Consulting Services Ltd | Professional & scientific | 2024 |
| Simon Skinner Limited | Professional & scientific | 2016 |
| Simplicity Works Ltd | Professional & scientific | 2023 |
| Simplifying Finance Ltd | Financial services | 2025 |
| Simply Stunning Flowers Ltd | Wholesale & retail | 2015 |
| Simpsons of London Limited | Extraterritorial | 2011 |
| Sinai Boat Ltd | Wholesale & retail | 2017 |
| Sinew Limited | Professional & scientific | 2016 |
| Site AID Ltd | Information & communication | 2025 |
| Site Mechanical Ltd | Construction | 2024 |
| Sixtyone Create Ltd | Professional & scientific | 2025 |
| SJ Holding Group Limited | Financial services | 2025 |
| SJK Carpentry & Sons Ltd | Manufacturing | 2021 |
| SJO Enterprises Limited | Financial services | 2010 |
| SJR Consulting Services Ltd | Professional & scientific | 2024 |
| SJR Essex Limited | Financial services | 2020 |
| SJW Energy Limited | Professional & scientific | 2019 |
| Skapari Ltd | Information & communication | 2025 |
| Skay Property Rentals Ltd | Real estate | 2025 |
| Skin Boss Ltd | Other services | 2016 |
| Skso Ltd | Transport & logistics | 2019 |
| Sky Vision Surveys Ltd | Administrative & support | 2016 |
| SL Hair Benfleet Limited | Other services | 2018 |
| SL Hair Leigh Limited | Education | 2020 |
| Slumberfleece Limited | Manufacturing | 1988 |
| SM Locks and Security Limited | Administrative & support | 2010 |
| Smallholdings Mews Management Ltd | Real estate | 2024 |
| Smart Integrity Ltd | Information & communication | 2023 |
| Smart Scaffolding & Safety Netting Limited | Professional & scientific | 2022 |
| Smart Scaffolding Ltd | Construction | 2011 |
| Smartflow AI Ltd | Information & communication | 2026 |
| Smith's Asphalt & Flat Roofing Ltd | Construction | 2022 |
| Smooth Botanica Ltd | Manufacturing | 2025 |
| Snag AID Ltd | Information & communication | 2025 |
| Snooker and Pool Table Company Limited | Wholesale & retail | 1983 |
| Snooker Sports (Manufacturing) Limited | Manufacturing | 2012 |