| Shaurya International Ltd | Health & social care | 2019 |
| SHC (UK) Limited | Professional & scientific | 2007 |
| Sheds Alive Limited | Construction | 2018 |
| Sheeran Media Ltd | Information & communication | 2024 |
| Shengo Limited | Health & social care | 2012 |
| Sherlocks Solutions Ltd | Health & social care | 2014 |
| Sherratt Pro Ltd | Wholesale & retail | 2024 |
| Sherwood Bros. and Burton (Maidenhead) Limited | Construction | 1964 |
| Sherwood Events Limited | Administrative & support | 2007 |
| Shieling Ltd | Administrative & support | 2018 |
| Shimmer Beauty Limited | Other services | 2023 |
| Shinfield Pharmaceuticals Ltd | Professional & scientific | 2014 |
| Shinfield Road Freehold Limited | Households | 2024 |
| Shiny Earth Ltd | Information & communication | 2024 |
| Shinytech Ltd | Information & communication | 2019 |
| Shiphaly Ltd | Information & communication | 2019 |
| Shirebrook Village NO.1 Residents Company Limited | Real estate | 1991 |
| Shires PES Ltd | Mining & quarrying | 2026 |
| Shiv RAM Restaurants Ltd | Hospitality | 2023 |
| Shivi Estates Ltd | Real estate | 2025 |
| Shivoham Properties Limited | Real estate | 2025 |
| Shmd Co Ltd | Real estate | 2024 |
| Shorewood Properties Limited | Real estate | 2025 |
| SHR3 Krupa House Limited | Manufacturing | 2023 |
| Shree Management Consulting Limited | Professional & scientific | 2024 |
| Shss Works Ltd | Other services | 2024 |
| Shuban Enterprises Ltd | Wholesale & retail | 2011 |
| Shubh Rathod Ltd | Information & communication | 2025 |
| Shurlock ROW Garage Ltd | Wholesale & retail | 2022 |
| Shuttle Planet Limited | Information & communication | 2016 |
| Shvetash Limited | Information & communication | 2010 |
| Si-Tec Plans Limited | Professional & scientific | 2004 |
| Siddhi Enterprises Limited | Wholesale & retail | 2012 |
| Side EYE Shady Ltd | Wholesale & retail | 2025 |
| Side Kick Stores Ltd | Wholesale & retail | 2023 |
| Sidebar Limited | Manufacturing | 2024 |
| Sidebell Capital Partners Limited | Professional & scientific | 2013 |
| Sidebell Limited | Professional & scientific | 1963 |
| Sideline Sport Ltd | Manufacturing | 2024 |
| Siennashuttersandblinds Ltd | Construction | 2024 |
| SIG Technologies Limited | Information & communication | 2018 |
| Signage Rocket Ltd | Information & communication | 2015 |
| Signals OPS Ltd | Information & communication | 2026 |
| Signals-Ai Ltd | Wholesale & retail | 2025 |
| Signature Executive Coaching Limited | Administrative & support | 2023 |
| Sikengele Ltd | Health & social care | 2014 |
| Silicon Storage Technology Ltd | Professional & scientific | 2017 |
| Silicon Validation Systems Limited | Professional & scientific | 2025 |
| Silk Place Management Company Limited | Households | 2005 |
| Siloam Construction Services Limited | Construction | 1998 |
| Silver Freeze Limited | Manufacturing | 2001 |
| Silver Grange (Finchampstead) Management Company Limited | Households | 1999 |
| Silver Stream Aviation Limited | Extraterritorial | 2023 |
| Silviu Dinita Barbers Ltd | Other services | 2022 |
| Simba Cleaning Services Ltd | Administrative & support | 2024 |
| Simior Holdco Ltd | Financial services | 2025 |
| Simmonds Mortgage Services Ltd | Financial services | 2018 |
| Simmonite Online Limited | Wholesale & retail | 2014 |
| Simmons Brewery Building Management Company Limited | Households | 2002 |
| Simon Procter Commercial Properties Ltd | Real estate | 2020 |
| Simone Surveys Limited | Transport & logistics | 1994 |
| Simple Urban Properties Ltd | Real estate | 2026 |
| Simplex Care Limited | Wholesale & retail | 2013 |
| Simplic Ltd | Administrative & support | 2007 |
| Simplicity Company Developments Limited | Professional & scientific | 2018 |
| Simply CX Ltd | Information & communication | 2020 |
| Simply French Online Ltd | Education | 2016 |
| Simply Green Landscapes Limited | Administrative & support | 2003 |
| Simply REG UK Ltd | Professional & scientific | 2026 |
| Simply Safer Limited | Information & communication | 2017 |
| Simply Sushi PAN Asian Limited | Hospitality | 2023 |
| Simpson and Family Construction Limited | Construction | 2026 |
| Simpson Springs & Pressings Limited | Manufacturing | 1980 |
| Sims Solar Limited | Construction | 2012 |
| Sinar Agritec (R&D) Limited | Manufacturing | 2013 |
| Sinclair Community Impact CIC | Water & waste | 2025 |
| Sindlesham Court (Trading) Limited | Hospitality | 2012 |
| Sindlesham Court Limited | Hospitality | 1969 |
| Singlewave Games Limited | Information & communication | 2019 |
| Singularity Tech Ltd | Information & communication | 2023 |
| Sircles.Net Limited | Information & communication | 2005 |
| Sirechez Properties Ltd | Real estate | 2024 |
| Sirigen II Limited | Financial services | 2012 |
| Sirius Cybernetics Ltd | Professional & scientific | 2023 |
| Sirius ERP Consultancy Limited | Professional & scientific | 2024 |
| Sitindigital LLP | | 2025 |
| Sivani Associates Limited | Information & communication | 2017 |
| Sivani Property Limited | Real estate | 2023 |
| SIX Mile Limited | Real estate | 2023 |
| Sixteen Rectory Road Drive Limited | Financial services | 2024 |
| SJ Educational Psychology Ltd | Education | 2022 |
| SJ Harris Joinery Limited | Construction | 2012 |
| SJN Insights Ltd | Information & communication | 2018 |
| SJR Specialist Consultants Limited | Mining & quarrying | 2011 |
| SK Berks Ltd | Wholesale & retail | 2023 |
| SK Insulation & Roofing Limited | Construction | 2025 |
| Skaero UK Limited | Financial services | 2019 |
| SKC Consultants Limited | Information & communication | 2019 |
| SKILLZ4LIFE Sports Coaching Limited | Health & social care | 2019 |
| Skinbyolivia Ltd | Other services | 2024 |