| S. Grundon (Waste) Limited | Professional & scientific | 1952 |
| S.Dorn Electrical Contractor Limited | Construction | 2025 |
| S.G.S Telemarketing Limited | Other services | 2020 |
| S2U Limited | Professional & scientific | 2019 |
| Safehire Limited | Other services | 2020 |
| Sage and Squash Catering Ltd | Hospitality | 2022 |
| Saldavai Ltd | Information & communication | 2025 |
| Sales-Talk Telemarketing Limited | Information & communication | 2011 |
| Salesstrategy.Tech Limited | Professional & scientific | 2019 |
| SAM & RTH Ltd | Hospitality | 2025 |
| Samantha Almond Ltd | Health & social care | 2024 |
| Samurai Capital Limited | Construction | 2024 |
| Sanctum Hair Limited | Other services | 2019 |
| Sandra Duggan Bespoke Soft Furnishings Ltd | Other services | 2018 |
| Santosha Wellbeing Ltd | Other services | 2019 |
| Sarah Blomfield Studio Ltd | Arts & recreation | 2022 |
| Sarah Packman Limited | Financial services | 2021 |
| Savernake Homes Limited | Construction | 2015 |
| Savernake Properties Limited | Real estate | 1988 |
| Savernake Properties NO8 Limited | Real estate | 2017 |
| SBM Networks Limited | Information & communication | 2016 |
| Scalamari Limited | Professional & scientific | 2001 |
| Scaleup Global Ltd | Information & communication | 2023 |
| Scotford & Teasdale Limited | Professional & scientific | 2004 |
| Scott & Scott Consulting Ltd | Professional & scientific | 2021 |
| Scott & Scott Holdings Ltd | Construction | 2020 |
| Screw in the Tuna Limited | Other services | 2022 |
| SDW Consulting Ltd | Information & communication | 2010 |
| Sea-Kit International Ltd | Manufacturing | 2017 |
| Seazone Solutions Limited | Professional & scientific | 2003 |
| Secure Payroll Limited | Professional & scientific | 2020 |
| Securipol Security Services Ltd | Administrative & support | 2002 |
| SEE More Potential Ltd | Information & communication | 2008 |
| Seed Rentals Ltd | Real estate | 2025 |
| Seiki Systems Limited | Information & communication | 2002 |
| Sensory Science Centre Limited | Professional & scientific | 2008 |
| SET Firm Limited | Information & communication | 2010 |
| Seventyfive Consulting Ltd | Professional & scientific | 2022 |
| Shake & Make Ltd. | Arts & recreation | 2019 |
| Shellfish COW Limited | Hospitality | 2019 |
| Shire Cleaning Group Ltd | Administrative & support | 2024 |
| Shire Hall (Newport) Limited Partnership | | 2012 |
| Shirescapes Ltd | Construction | 2021 |
| Shooting Lodge Productions Ltd | Information & communication | 2016 |
| Showland (Chichester) Limited | Real estate | 2004 |
| Showland (Wakefield) Limited | Real estate | 2013 |
| Showland Investments Limited | Real estate | 2008 |
| Showland Limited | Real estate | 1996 |
| Showland Limited Partnership | | 2011 |
| Showland Tewkesbury Limited Partnership | | 2024 |
| Shute Consulting Ltd | Hospitality | 2012 |
| Silverbacks Solutions Ltd | Administrative & support | 2025 |
| Silverbeach Limited | Health & social care | 2015 |
| Simhe Events Ltd | Administrative & support | 2026 |
| Simply Creating Change Ltd | Professional & scientific | 2014 |
| Sinodun Consulting Limited | Professional & scientific | 2010 |
| SIX Box Media Ltd | Administrative & support | 2012 |
| SJB Studio Limited | Information & communication | 2026 |
| Sjmacauley.Org Ltd | Health & social care | 2012 |
| SK & JK Consulting Ltd | Professional & scientific | 2025 |
| SKG Entertainment Ltd | Arts & recreation | 2015 |
| Sky Stand Limited | Other services | 2022 |
| Skysignal Ltd | Information & communication | 2026 |
| Slapj Limited | Information & communication | 2022 |
| SLC Strategies Limited | Professional & scientific | 2025 |
| Small Business Britain Ltd | Professional & scientific | 2016 |
| Small IS Big CIC | Professional & scientific | 2014 |
| Smart Monkeys Business Services Limited | Professional & scientific | 2013 |
| Smart Parts UK (Limited) Ltd | Wholesale & retail | 2025 |
| Smithcarey Limited | Administrative & support | 2009 |
| Smithy Ltd | Information & communication | 2025 |
| SN Mortgages & Financial Services Ltd | Financial services | 2002 |
| Snip Records Limited | Arts & recreation | 2006 |
| Sofability Limited | Real estate | 1988 |
| Soladar Homes Ltd | Real estate | 2021 |
| Somerville Air Conditioning Ltd | Extraterritorial | 2011 |
| Somerville Building Services Limited | Construction | 2003 |
| SOS Cleaning Contracts Ltd | Administrative & support | 2023 |
| Sothis Press Limited | Information & communication | 2023 |
| Sotil's (Croft) Ltd | Wholesale & retail | 2008 |
| Sotwell Consulting Limited | Information & communication | 2025 |
| South Oxfordshire Brewery Ltd | Wholesale & retail | 2020 |
| Speakers Collective CIC | Other services | 2019 |
| Speculative Simulations Ltd | Information & communication | 2017 |
| Spica Tech Services Limited | Information & communication | 2014 |
| Spice Garden Benson Ltd | Hospitality | 2017 |
| Spillaway Projects Limited | Water & waste | 2010 |
| Spot on Transport Limited | Transport & logistics | 2022 |
| SPR Expeditions Ltd | Administrative & support | 2014 |
| Spring Cottage Cakes & Bakes Ltd | Manufacturing | 2021 |
| SSR & N Ltd | Professional & scientific | 2018 |
| ST John's Academy Trust | Education | 2013 |
| ST John's House (Wallingford) Management Company Limited | Other services | 2004 |
| ST John's Road Wallingford Ltd | Professional & scientific | 2011 |
| ST Tudy Inn Ltd | Hospitality | 2021 |
| ST. Leonard's Court Wallingford Limited | Real estate | 1973 |
| Stafford Lawrence Limited | Administrative & support | 2017 |
| Station Hostel Limited | Hospitality | 2022 |
| Stewart Global Properties Limited | Real estate | 2006 |
| Stockcroft Limited | Agriculture & fishing | 2011 |