| SET 2 Build Limited | Information & communication | 2012 |
| Setray Ltd | Construction | 2013 |
| Seventeen Consulting Limited | Professional & scientific | 2012 |
| Seventh Step Agency Ltd | Information & communication | 2026 |
| Sewell & Gardner Limited | Real estate | 2011 |
| Sewing Online Ltd | Manufacturing | 2004 |
| Seyah Limited | Administrative & support | 2022 |
| Seylua Ltd | Arts & recreation | 2025 |
| SFX FPV Limited | Information & communication | 2018 |
| Sghrv Ltd | Information & communication | 2024 |
| SH Collective Ltd | Wholesale & retail | 2025 |
| Shadow Rackets Limited | Wholesale & retail | 2026 |
| Shadowvault Cyber Defence Ltd | Information & communication | 2025 |
| Shakespeare Decorating Co Limited | Construction | 2012 |
| Shalex Harrow Ltd | Real estate | 2026 |
| Shalin Designs Ltd | Information & communication | 2021 |
| Shanthini & Associates Limited | Professional & scientific | 2022 |
| Sharbo & Sons UK Ltd | Transport & logistics | 2025 |
| Sharnbrook Care Home Limited | Health & social care | 2009 |
| Sharp Consulting Limited | Professional & scientific | 2020 |
| Shavelord Limited | Real estate | 1986 |
| Shays Salon Ltd | Other services | 2022 |
| SHC Accountants Limited | Professional & scientific | 2018 |
| Sheikh Associates Limited | Professional & scientific | 2002 |
| Shelly Investments Limited | Real estate | 2020 |
| Shen Consultancy Ltd | Health & social care | 2015 |
| Shepherd VFX Ltd | Information & communication | 2016 |
| Shigar Ltd | Information & communication | 2015 |
| Shila Investments Limited | Real estate | 2019 |
| Shine Rigging Limited | Construction | 2025 |
| Shining Armour MGT Ltd | Professional & scientific | 2024 |
| Ship Street Properties Ltd | Real estate | 2025 |
| Shish of Ricky Limited | Hospitality | 2025 |
| Shivi Consulting Services Ltd | Information & communication | 2015 |
| Shivi Realty Group Ltd | Real estate | 2019 |
| Shivik Consultancy Ltd | Information & communication | 2019 |
| Shoolin Media House Ltd | Information & communication | 2021 |
| Shorehouse Ltd | Hospitality | 2021 |
| Shrak Ltd | Wholesale & retail | 2021 |
| Shree Vallabh Vaibhav Ltd | Professional & scientific | 2007 |
| Shreyas IT Limited | Information & communication | 2008 |
| Shri Asha Integrated Ayurveda Limited | Health & social care | 2020 |
| Shri Asha Integrated Wellness Limited | Administrative & support | 2014 |
| Shrirup Enterprises Ltd | Real estate | 2026 |
| Shubra Limited | Manufacturing | 2013 |
| SI SI Harding Property Limited | Real estate | 2003 |
| Sian Interiors Limited | Professional & scientific | 2026 |
| Sicol Consulting Limited | Wholesale & retail | 2016 |
| Sidhiridhi Limited | Other services | 2024 |
| Sidqas Ltd | Health & social care | 2020 |
| Siena Accounting Ltd | Professional & scientific | 2021 |
| Sigkern Limited | Information & communication | 2019 |
| Silhouette Technologies Limited | Information & communication | 2017 |
| Silk Mango Ltd | Wholesale & retail | 2021 |
| Silver and Rock Ltd | Professional & scientific | 2025 |
| Silver Enterprises Limited | Wholesale & retail | 1995 |
| Silverback-Creative Ltd | Professional & scientific | 2014 |
| Silvergreen Creations Limited | Wholesale & retail | 2023 |
| Silversaw Limited | Construction | 2015 |
| Silversprings RCH Ltd. | Health & social care | 2008 |
| Silverstar Properties Ltd | Real estate | 2024 |
| Simay Ltd | Other services | 2020 |
| Simon Dunn Groundworks & Services Ltd | Construction | 2018 |
| Simon Myers Coaching Ltd | Professional & scientific | 2026 |
| Simon Sowden Limited | Professional & scientific | 2014 |
| Simply Uchip Ltd | Information & communication | 2021 |
| Sircal Limited | Wholesale & retail | 2025 |
| Sirdar Mews (Southampton) Management Limited | Households | 2010 |
| Site Calcs Ltd | Professional & scientific | 2025 |
| Site Service Regions Ltd | Water & waste | 2026 |
| SIX Langland Gardens Limited | Real estate | 1995 |
| Sixnorth Limited | Professional & scientific | 1985 |
| Sixteen Churchfield Ltd | Construction | 2015 |
| Sixteen Churchfield Management Limited | Real estate | 2022 |
| Sixth Avenue Business Park Ltd | Real estate | 2023 |
| Sixth Avenue Halstead Ltd | Real estate | 2017 |
| SJ Premium Properties Ltd | Real estate | 2021 |
| Sjbp Ltd | Administrative & support | 2019 |
| SJY Property Solutions Ltd | Households | 2025 |
| SK Carpentry Ltd | Construction | 2025 |
| SKC 1 Ltd | Real estate | 2024 |
| SKC Solutions Limited | Professional & scientific | 2005 |
| Skey Property Ltd | Real estate | 2024 |
| Skin Transform Ltd | Health & social care | 2013 |
| Skinglo Aesthetics Limited | Health & social care | 2024 |
| Skinner & Co (Accountants) Limited | Professional & scientific | 2011 |
| SKP Development Ltd | Construction | 2025 |
| SKS Online Ltd | Wholesale & retail | 2024 |
| Skyclean Aerial Services Ltd | Information & communication | 2025 |
| Skyflash Limited | Professional & scientific | 2013 |
| Skyfox Data Systems Ltd | Information & communication | 2019 |
| Skylord Investments Limited | Real estate | 2003 |
| Skylord Properties Ltd | Real estate | 2022 |
| Skylord Travel PLC | Administrative & support | 1988 |
| Skypets International Limited | Transport & logistics | 2021 |
| Sliabh Construction (Chorleywood) Limited | Construction | 2018 |
| Sliabh Construction Limited | Construction | 2006 |
| Slimco Automotive Services Ltd | Wholesale & retail | 2024 |
| SLM Housing Limited | Other services | 2005 |
| Smart Choice Logistics Ltd | Transport & logistics | 2019 |