| Rycote Services Limited | Agriculture & fishing | 2012 |
| S & P Consultancy (UK) Limited | Professional & scientific | 2004 |
| S Aylen Consulting Limited | Professional & scientific | 2017 |
| S Cole Anaesthetics Ltd | Health & social care | 2026 |
| S&K Equity Ltd | Financial services | 2023 |
| S&T Empire Ltd | Real estate | 2021 |
| S.A.F.E.T. Services Limited | Construction | 2006 |
| S.D. Timmo Car Sales Limited | Wholesale & retail | 2003 |
| Sageflowers Ltd | Wholesale & retail | 2018 |
| Salden Farm Limited | Agriculture & fishing | 1995 |
| Salience Labs Ltd | Professional & scientific | 2020 |
| Salix Advisory Limited | Professional & scientific | 2022 |
| Sally Conran Studio Limited | Professional & scientific | 2018 |
| SAM Harper Music Ltd | Information & communication | 2023 |
| SAM Taylor Animation Ltd | Information & communication | 2024 |
| SAM Willis Design Ltd | Professional & scientific | 2025 |
| Sam-W Limited | Professional & scientific | 2016 |
| Samson Equipment Ltd | Manufacturing | 2016 |
| Sarah Illingworth Limited | Financial services | 2003 |
| Sarratt Management Limited | Professional & scientific | 2005 |
| Sarratt Online Limited | Wholesale & retail | 2018 |
| SAS Wireless Limited | Professional & scientific | 2019 |
| Sbgneuro Limited | Health & social care | 2012 |
| Scancross (Environmental Services) Limited | Construction | 1985 |
| Scancross Asbestos Surveys Ltd | Water & waste | 2026 |
| Scanlab Ltd | Extraterritorial | 2011 |
| Scanlab Projects Ltd | Professional & scientific | 2011 |
| Schultmay Ltd | Professional & scientific | 2016 |
| Scotched Ltd | Hospitality | 2024 |
| Scott&Young Ltd | Wholesale & retail | 2025 |
| Screen 13 Consultancy Limited | Administrative & support | 2018 |
| SDM International Ltd | Transport & logistics | 2007 |
| Search Care Ltd | Information & communication | 2012 |
| Seasonal Acres Limited | Arts & recreation | 2013 |
| Second Cousins Ltd | Professional & scientific | 2013 |
| Secure Vending Solutions Ltd | Wholesale & retail | 2025 |
| Security Shutter Expert Ltd | Manufacturing | 2015 |
| Seekings Plumbing Services Limited | Construction | 2024 |
| Seemtec Ltd | Professional & scientific | 2026 |
| Seidasan Ltd | Information & communication | 2025 |
| Select Heating Services Limited | Construction | 2008 |
| Select Stock Limited | Professional & scientific | 2021 |
| Selka Health Ltd | Professional & scientific | 2025 |
| Send at Heart Consulting Ltd | Education | 2025 |
| Sensel Studio Limited | Information & communication | 2015 |
| Seriously Curious Ltd | Education | 2016 |
| Seth & Wheldon Ltd | Real estate | 2025 |
| Sewgroup Limited | Extraterritorial | 2022 |
| Seymour Productions Limited | Information & communication | 2011 |
| Sgfvc Ltd | Construction | 2025 |
| SGS Heating and Plumbing Ltd | Construction | 2020 |
| Shalyn Limited | Professional & scientific | 2021 |
| Sham's Bros Limited | Real estate | 2023 |
| Sharp Consumer Electronics UK Limited | Other services | 2017 |
| Sharp Tree Care Ltd | Administrative & support | 2020 |
| Shaun Glover Ltd | Professional & scientific | 2019 |
| SHE Drew That Ltd | Professional & scientific | 2021 |
| Shedden Studio Ltd | Professional & scientific | 2025 |
| Shellflowerstore Ltd | Arts & recreation | 2025 |
| Shepperton Physio Ltd | Health & social care | 2024 |
| Shepperton Physiotherapy Ltd | Health & social care | 2023 |
| Sherlock Combs Ltd | Wholesale & retail | 2013 |
| Shire Stables Limited | Agriculture & fishing | 2019 |
| Short & SON Homes Ltd | Construction | 2024 |
| Shrimpton International Developments Ltd | Professional & scientific | 2015 |
| Sigma Lithium Limited | Professional & scientific | 2013 |
| Signal Biometrics Ltd | Professional & scientific | 2016 |
| Signatur Biosciences Ltd | Professional & scientific | 2022 |
| Signature Landscapes and Fencing Ltd | Administrative & support | 2025 |
| Silent View Windows Commercial Ltd | Construction | 2022 |
| Silent View Windows Holdings Limited | Financial services | 2024 |
| Silent View Windows Ltd | Construction | 2012 |
| Silk-Leadwork Limited | Construction | 2019 |
| Silverline Research Ltd | Professional & scientific | 2024 |
| Simmarcom Limited | Information & communication | 2014 |
| Simon Wheeldon Ltd | Professional & scientific | 2026 |
| Simone Ltd | Professional & scientific | 2019 |
| Simply Parts Limited | Administrative & support | 2005 |
| Simton Limited | Manufacturing | 2018 |
| Singtali Investments Ltd | Real estate | 2016 |
| SIX Sevens Solutions Ltd | Information & communication | 2019 |
| Size Clarke Partnership LLP | | 2019 |
| SJE Holdings Limited | Administrative & support | 2017 |
| Sjmw Ltd | Information & communication | 2025 |
| SJS Accountants Limited | Professional & scientific | 2020 |
| SK Venture Capital Limited | Information & communication | 2021 |
| Skyey Limited | Real estate | 2004 |
| Slater Thomas Holdings Limited | Financial services | 2026 |
| Smart Electrical Services Oxfordshire Limited | Construction | 2024 |
| Smattglock Property Investment Ltd | Real estate | 2022 |
| Smile Freely (Thame) Ltd | Health & social care | 2011 |
| Smoochy MOO Moos Ltd | Hospitality | 2021 |
| Smoove Limited | Information & communication | 2010 |
| Snowbooks Limited | Information & communication | 2002 |
| Softly Surman Properties Ltd | Real estate | 2014 |
| Solebay Design Systems Limited | Professional & scientific | 1995 |
| Something Goes Right Ltd | Arts & recreation | 2023 |
| Something More Near Limited | Professional & scientific | 2016 |
| Sonder Experience Ltd | Other services | 2026 |
| Sonichem Technologies Limited | Professional & scientific | 2007 |