| Sidar Property Investment Limited | Real estate | 2024 |
| Sidh Overseas (UK) Ltd | Wholesale & retail | 2018 |
| Sient Technologies Limited | Information & communication | 2020 |
| Sigmaa Business Services Ltd | Real estate | 2021 |
| Signature Blush London Ltd | Other services | 2024 |
| Signature Paws Ltd | Wholesale & retail | 2023 |
| Signature Sauce Limited | Manufacturing | 2026 |
| Silvatec Ltd | Wholesale & retail | 2021 |
| Silveroaks Elite Care Ltd | Administrative & support | 2026 |
| SIM Golf Events Limited | Arts & recreation | 2025 |
| Simanson Ltd | Financial services | 2020 |
| Simapro UK Ltd | Information & communication | 2010 |
| Simon & Simon Property Services Limited | Real estate | 2020 |
| Simonharry Limited | Construction | 2025 |
| Simple Serve Ltd | Wholesale & retail | 2026 |
| Simple UP Qualifications Ltd | Education | 2021 |
| Sinead O'Brien HR Consultancy & Coaching Ltd | Administrative & support | 2020 |
| Singer Investments Ltd | Real estate | 2021 |
| Single OR Double Cocktail Delivery Limited | Wholesale & retail | 2020 |
| Sinmer UK Limited | Health & social care | 2020 |
| Siona Realty Limited | Real estate | 2021 |
| Sirr Sana Sanctuary Limited | Health & social care | 2024 |
| Sisk Social Work Consulting Limited | Health & social care | 2012 |
| SIX Foot Limited | Professional & scientific | 2023 |
| SIX Sells Limited | Administrative & support | 2020 |
| Sixteenfifty Limited | Professional & scientific | 2017 |
| SJC Group Ltd | Construction | 2026 |
| SJF Rigging Ltd | Construction | 2022 |
| SJK Residential Ltd | Real estate | 2020 |
| SJS Strategies Ltd | Professional & scientific | 2019 |
| Sjuk Investments Limited | Real estate | 2021 |
| SJW Mech Ltd | Construction | 2023 |
| SK Accounting Services Limited | Professional & scientific | 2012 |
| SK Properties and Investment Limited | Construction | 2018 |
| Skills Ninja Limited | Information & communication | 2024 |
| SKJ Developments Ltd | Construction | 2025 |
| SKU Electrical Ltd | Construction | 2019 |
| Sky Group Construction Ltd | Construction | 2021 |
| Skylift Solutions Limited | Information & communication | 2025 |
| Skystone Homes Ltd | Construction | 2018 |
| Slab Region Ltd | Wholesale & retail | 2026 |
| SLC Developments Ltd | Real estate | 2025 |
| SLG Petrochemical Limited | Wholesale & retail | 1986 |
| Slice Management Ltd | Professional & scientific | 2026 |
| Slim Monkey Limited | Wholesale & retail | 2018 |
| Slimetooshine Cleaning Specialists Ltd | Administrative & support | 2024 |
| SM6 Ltd | Professional & scientific | 2018 |
| Smaassetgroup.Com Ltd | Financial services | 2025 |
| Smart and Digital Business Ideas Ltd | Information & communication | 2020 |
| Smart Eco Build Ltd | Administrative & support | 2017 |
| Smart Health Solutions Limited | Health & social care | 2013 |
| Smartpik Limited | Wholesale & retail | 2025 |
| Smartx Group Limited | Information & communication | 2024 |
| Smiles for U (UK) Limited | Health & social care | 2007 |
| Smith Bellerby Ltd | Professional & scientific | 2001 |
| SMK (S&M) Properties Ltd | Real estate | 2022 |
| SN Intelligence Consultancy Limited | Information & communication | 2012 |
| Snake Management Limited | Real estate | 2001 |
| Snipers Gym Ltd | Other services | 2025 |
| Snpelectrical Ltd | Construction | 2018 |
| SNS Builders Ltd | Construction | 2026 |
| Soar&Union Ltd | Transport & logistics | 2021 |
| Sobeetrath Limited | Professional & scientific | 2025 |
| Social Policy Group Ltd | Professional & scientific | 2011 |
| Softek Consultancy Ltd | Real estate | 2013 |
| Softigence Ltd | Information & communication | 2014 |
| Solar Systems IT Limited | Information & communication | 2009 |
| Solution Provider Healthcare Ltd | Health & social care | 2022 |
| Solvent Health Limited | Education | 2025 |
| Sons of Rigor Productions LLP | | 2014 |
| Sophia Elizabeth Ltd | Health & social care | 2022 |
| Sophie-Belle Limited | Wholesale & retail | 2020 |
| Sornam Limited | Real estate | 2026 |
| SOS Security Ltd | Administrative & support | 2016 |
| Soul Royalty Ltd | Arts & recreation | 2022 |
| Sounds Alarming (UK) Limited | Wholesale & retail | 2000 |
| Sourcing Group Limited | Financial services | 2017 |
| South London Driving School Ltd | Administrative & support | 2016 |
| Southbank Photo Limited | Extraterritorial | 2002 |
| Southeast Tree Care Limited | Agriculture & fishing | 2014 |
| Southern Construction Group Ltd | Construction | 2025 |
| Southern Safety Centres Limited | Wholesale & retail | 1983 |
| Southern Van Lines (2006) Limited | Transport & logistics | 2006 |
| Southwood Technologies Ltd | Information & communication | 2020 |
| Souvlaki Place Ltd | Hospitality | 2025 |
| Sovereign Equity Holdings Limited | Professional & scientific | 2012 |
| SP Universe Ltd | Professional & scientific | 2023 |
| SP88 Limited | Wholesale & retail | 2022 |
| Spark Properties Ltd | Real estate | 2017 |
| Spark Publishing Ltd | Information & communication | 2025 |
| Sparkle Group Solutions Ltd | Administrative & support | 2025 |
| Sparkles Daycare (Wallington) Ltd | Health & social care | 2023 |
| Specialist Corner Ltd | Wholesale & retail | 2023 |
| Speed Data Solutions Ltd | Construction | 2024 |
| Speedy Executive Ride Limited | Transport & logistics | 2025 |
| Sphk Properties Ltd | Real estate | 2025 |
| Spice HUT Ltd | Hospitality | 2017 |
| Spinel Ltd | Real estate | 2026 |
| Spinola & SON Ltd | Real estate | 2019 |
| Spjp Properties Ltd | Real estate | 2018 |