| Sleeper Benches Limited | Manufacturing | 2019 |
| SLH Projects Ltd | Construction | 2023 |
| SLK Sunshine Limited | Health & social care | 2018 |
| SLM Home Improvements Ltd | Construction | 2024 |
| Slotstake Residents Management Limited | Real estate | 1988 |
| SLS Recruitment Ltd | Administrative & support | 2012 |
| Sltc Maintenance Limited | Construction | 2024 |
| SLV20 Ltd | Transport & logistics | 2020 |
| SLW Legal Limited | Professional & scientific | 2023 |
| SM Socials Ltd | Information & communication | 2025 |
| Smajo UK Limited | Information & communication | 2018 |
| Small Business Geek Limited | Professional & scientific | 2021 |
| Small Thorn Place Management Company Limited | Households | 2019 |
| Smart Automotive Repairs Limited | Manufacturing | 2015 |
| Smart Bodyworkz Limited | Wholesale & retail | 2011 |
| Smart Building Control Services Ltd | Professional & scientific | 2022 |
| Smart Computex Ltd | Information & communication | 2025 |
| Smart Design and Build Essex Ltd | Construction | 2017 |
| Smart Dojos Ltd | Education | 2022 |
| Smart Group Holdings Limited | Construction | 2024 |
| Smart Heat Limited | Administrative & support | 2016 |
| Smart Life Solutions Ltd | Information & communication | 2015 |
| Smart Minds Youth Support & Mentoring Services Ltd | Education | 2022 |
| Smart Motor Service Ltd | Wholesale & retail | 2021 |
| Smart Move Logistics Limited | Transport & logistics | 2025 |
| Smart Networked Environments Ltd | Information & communication | 2010 |
| Smart Scuffs 2015 Limited | Wholesale & retail | 2015 |
| Smart Services (London) Limited | Professional & scientific | 2011 |
| Smart&Christopher Limited | Information & communication | 2013 |
| Smartadvance Property Management Limited | Households | 1992 |
| Smarter Travel Limited | Professional & scientific | 2015 |
| Smarter Way Mentors Limited | Professional & scientific | 2020 |
| Smartresilience Ltd | Information & communication | 2018 |
| Smartsteph Ltd | Health & social care | 2024 |
| Smartt Technologies Limited | Information & communication | 2015 |
| Smashed CHELMSFORD1 Ltd | Hospitality | 2025 |
| Smashed Essex Ltd | Hospitality | 2024 |
| Smashed Wivenhoe Limited | Hospitality | 2025 |
| SMB HR Services Limited | Administrative & support | 2017 |
| Smd-Eagle Ltd | Transport & logistics | 2023 |
| Smdl Properties Ltd | Real estate | 2024 |
| Smile Healthcare Services Ltd | Administrative & support | 2022 |
| Smiley Car and Commercial Limited | Wholesale & retail | 2002 |
| SMILEZ121 Ltd | Health & social care | 2024 |
| Smith and Coulson Limited | Information & communication | 2022 |
| Smith and SON Gardens Ltd | Administrative & support | 2026 |
| Smith Build Construction Limited | Construction | 2022 |
| Smith Family Ltd | Wholesale & retail | 2021 |
| Smith Group Developments Ltd | Real estate | 2021 |
| Smith Kerins Ltd | Information & communication | 2024 |
| Smith Medical Limited | Health & social care | 2010 |
| Smiths Healthcare Limited | Wholesale & retail | 2007 |
| Smjd Nexus Limited | Wholesale & retail | 2025 |
| SMK Enterprises Limited | Health & social care | 2025 |
| SML GAS Ltd | Construction | 2020 |
| SMM Indigo Services and Investments Ltd | Information & communication | 2025 |
| Smoke and Fire Events Limited | Arts & recreation | 2020 |
| Smoke Ventilation Consultancy Ltd | Professional & scientific | 2018 |
| Smooth Finish GRP Ltd | Manufacturing | 2014 |
| Smooth Pebble Properties Ltd | Real estate | 2018 |
| Smooth Tune (Colchester) Limited | Wholesale & retail | 2016 |
| SMP Contractors Ltd | Administrative & support | 2021 |
| SMR Refrigeration Limited | Other services | 2002 |
| Smrk Limited | Information & communication | 2018 |
| SMS Grounds & Property Maintenance Ltd | Administrative & support | 2024 |
| SMS Tree Services Ltd | Administrative & support | 2018 |
| Smugglers Gold Limited | Extraterritorial | 2011 |
| Smugglers Wharf Freehold Limited | Households | 2021 |
| SMW Financial Planning Ltd | Financial services | 2011 |
| Smwhitehead Ltd | Professional & scientific | 2025 |
| Smyth Trading Ltd | Financial services | 2013 |
| Snag Savy Limited | Construction | 2020 |
| Snaggedit Ltd | Information & communication | 2025 |
| Snake IT Europe Limited | Manufacturing | 2012 |
| Snapper Productions Limited | Information & communication | 2012 |
| Snatchd House Ltd | Professional & scientific | 2016 |
| Snell Consulting Ltd | Professional & scientific | 2026 |
| Snifora Limited | Wholesale & retail | 2025 |
| Snoopies Ltd | Professional & scientific | 2008 |
| Snowdon GAS & Heating Services Ltd | Construction | 2009 |
| Snows Collectables Ltd | Wholesale & retail | 2025 |
| Snusway Ltd | Wholesale & retail | 2022 |
| Snvk Cafe Ltd | Hospitality | 2026 |
| SO Fresh Cleaning Service Ltd | Administrative & support | 2025 |
| SO Green Property Ltd | Real estate | 2024 |
| SO Medical Aesthetics Ltd | Health & social care | 2016 |
| Soakaways Limited | Extraterritorial | 2022 |
| Soap and Suds Ltd | Other services | 2025 |
| Social Brands (GB) Ltd | Wholesale & retail | 2020 |
| Social Impact Corporation Limited | Professional & scientific | 2021 |
| Socially Brave Group Limited | Professional & scientific | 2021 |
| SOCIALSINCE90 Ltd | Wholesale & retail | 2021 |
| Society of Mesotherapy of the United Kingdom | Other services | 2013 |
| Sofa King Comfy Limited | Wholesale & retail | 2026 |
| Sofastyle Ltd | Manufacturing | 2016 |
| Softdev Solutions Ltd | Information & communication | 2024 |
| Softview Conservatories Windows & Doors Limited | Construction | 1996 |
| Softview Direct Ltd | Extraterritorial | 2023 |
| Softvize Academy Ltd | Information & communication | 2025 |
| Softvize Ltd | Information & communication | 2024 |