| Second Front Media Ltd | Wholesale & retail | 2015 |
| Secondform Ltd | Information & communication | 2025 |
| Secret Music Limited | Wholesale & retail | 2004 |
| Sector (UK) Limited | Information & communication | 1991 |
| Secure and Grow Limited | Professional & scientific | 2026 |
| Seecoy Marketing Limited | Professional & scientific | 2010 |
| SEED1 CIC | Wholesale & retail | 2019 |
| Self Centred Limited | Administrative & support | 2012 |
| Sennheiser UK Limited | Wholesale & retail | 1990 |
| Serafin Holdings Limited | Financial services | 2023 |
| Serafina Digital Ltd | Information & communication | 2025 |
| Serendipity Designs Limited | Wholesale & retail | 2023 |
| Serengeti Entertainment Limited | Information & communication | 2010 |
| Serval Automotive Ltd | Professional & scientific | 2011 |
| Serval Limited | Information & communication | 1998 |
| SG Amor Ltd | Real estate | 2020 |
| SG Sunray Ltd | Real estate | 2020 |
| SGH Consult Ltd | Other services | 2025 |
| Shadow Horse Partners LLP | | 2011 |
| Shared Intentions Ltd | Professional & scientific | 2024 |
| Shaun Andrews Design Limited | Professional & scientific | 2020 |
| Shaw Creativ Ltd | Manufacturing | 2013 |
| Sheepridge Holdings Limited | Financial services | 2025 |
| Shillingridge Associates Limited | Administrative & support | 2021 |
| Shillingridge Stables Limited | Hospitality | 2017 |
| Shinden Clinic Ltd | Health & social care | 2021 |
| Shop for Frames Ltd | Wholesale & retail | 2019 |
| Shott Trinova Holdings Limited | Professional & scientific | 2020 |
| Shrubbery Road Limited | Real estate | 2020 |
| Signal Walk Management Limited | Households | 2017 |
| Silkwood Developments Limited | Construction | 1986 |
| Silva Bond Limited | Professional & scientific | 2013 |
| Silvaback Consulting Ltd | Wholesale & retail | 2024 |
| Silver Cat Properties Limited | Real estate | 2018 |
| Silversmith Short Stay Ltd | Information & communication | 2015 |
| Simon Hunt Electrical Ltd | Construction | 2014 |
| Simons & Denville Properties Ltd | Real estate | 2021 |
| Simons-Denville Ltd | Extraterritorial | 2012 |
| Simply Category Ltd | Professional & scientific | 2019 |
| Simply Famous Limited | Wholesale & retail | 2016 |
| Siwal Ltd | Information & communication | 2020 |
| SJ Change Solutions Limited | Professional & scientific | 2012 |
| SJ Event Holdings Ltd | Financial services | 2026 |
| SJW Forex Trading Ltd | Professional & scientific | 2024 |
| Skazka Limited | Real estate | 2006 |
| SKD Design Limited | Professional & scientific | 2015 |
| SKG Scaffolding Ltd | Construction | 2025 |
| Skinstad Consulting Limited | Professional & scientific | 2025 |
| Skyeave Limited | Households | 1982 |
| Skygate Financial Limited | Professional & scientific | 2009 |
| Skyknot Ltd | Real estate | 2020 |
| Skylines UK Ltd | Professional & scientific | 2005 |
| SLB Coaching & Organisational Development Ltd | Professional & scientific | 2016 |
| SLK Team Construction Ltd | Construction | 2023 |
| Small Planet Developments Limited | Construction | 2015 |
| Smart Move Property Solutions Ltd | Households | 2020 |
| Smart Move Sourcing Ltd | Real estate | 2024 |
| Smart Pet Care Limited | Other services | 2008 |
| Smith International Holdings Ltd | Financial services | 2020 |
| Smithers Comms Ltd | Information & communication | 2022 |
| Smorgasbord Investments Limited | Financial services | 2021 |
| SMP73 Ltd | Professional & scientific | 2023 |
| Snapdragon Accounting Limited | Professional & scientific | 2014 |
| SO Consulting Services Ltd | Professional & scientific | 2020 |
| Softcat PLC | Information & communication | 1987 |
| Softcom Plus Limited | Information & communication | 1997 |
| Sojabe Ltd | Professional & scientific | 2026 |
| Solarbility Ltd | Construction | 2022 |
| Solutions & Services Ltd | Information & communication | 2002 |
| Solve International Trade London Limited | Wholesale & retail | 2023 |
| Somatrix Ltd | Professional & scientific | 2022 |
| Somerlea Court Road Maidenhead Management Company Limited | Households | 2003 |
| Sonova Consumer Hearing UK Limited | Manufacturing | 2021 |
| Sopalmo Limited | Arts & recreation | 2006 |
| Sophia Training & Consulting Ltd | Information & communication | 2023 |
| Sound Bites Events Limited | Administrative & support | 2025 |
| South Coast Breaks Ltd | Real estate | 2008 |
| South East Hockey Limited | Arts & recreation | 2021 |
| South Kensington Property Management Limited | Real estate | 2007 |
| Southern Actor Limited | Wholesale & retail | 2015 |
| Southview Portfolio Ltd | Real estate | 2022 |
| Souza Services Limited | Health & social care | 2012 |
| Sovereign Park Management Limited | Households | 1986 |
| Space Wrks Ltd | Information & communication | 2019 |
| Spade Oak Construction Ltd | Construction | 2026 |
| Spade Oak Duracourt Ltd | Construction | 2026 |
| Span Training & Development Limited | Education | 2001 |
| Spark Etail Limited | Wholesale & retail | 2011 |
| Spce 8 Ltd | Hospitality | 2019 |
| Spearhead Electrical Ltd | Manufacturing | 2020 |
| Specialist HIP Services Ltd | Health & social care | 2023 |
| Specialist Pain Clinics Limited | Health & social care | 2020 |
| Specialist Pain Experts Limited | Health & social care | 2025 |
| Spectrum Associated Suppliers Limited | Construction | 2012 |
| Spencer Close Management Company Limited | Households | 2022 |
| Spin Master Toys UK Limited | Wholesale & retail | 2004 |
| Spin One Holdings Limited | Administrative & support | 2024 |
| Spincode Limited | Information & communication | 2013 |
| Spinfield Consulting Marlow Ltd | Professional & scientific | 2021 |
| Spittal Street (Marlow) Residents Management Company Limited | Households | 2018 |