| Serein Ltd | Administrative & support | 2015 |
| Serein Private LLP | | 2016 |
| Sesum Limited | Wholesale & retail | 2018 |
| Setcrarn Limited | Real estate | 2008 |
| Seuss Consulting Ltd | Professional & scientific | 2022 |
| Sevenred Limited | Arts & recreation | 2025 |
| Seward Property Holdings Ltd | Real estate | 2020 |
| Seymour Place Services Limited | Households | 2018 |
| Sezan PG Ltd | Real estate | 2021 |
| Sgakona Ltd | Education | 2023 |
| SGL Consulting Limited | Information & communication | 2003 |
| SGS Rental Properties Ltd | Real estate | 2026 |
| SH Plots Wantage Limited | Construction | 2021 |
| Shackleton Consulting & Development Limited | Professional & scientific | 2016 |
| Shaded Fitness Ltd | Arts & recreation | 2024 |
| Shalbourne Property Management Limited | Real estate | 1998 |
| Shanks & Grantham Consulting Limited | Professional & scientific | 2010 |
| Shannon's Scrumptious Soaps Limited | Manufacturing | 2019 |
| Sharecare Limited | Professional & scientific | 1999 |
| Shaw Mill Freehold Limited | Real estate | 2013 |
| Shawgate Investments Ltd | Professional & scientific | 2022 |
| Shawn Foster Plumbing & Heating Ltd | Construction | 2023 |
| Shcw Ltd | Real estate | 2025 |
| Shearbridge Ltd | Real estate | 2019 |
| Sheepdown Management Company Limited | Households | 2000 |
| Shefford Lodge Limited | Households | 1999 |
| Shefs Limited | Hospitality | 2025 |
| Sheikh 2025 Limited | Hospitality | 2025 |
| Sheldon Phillips Limited | Administrative & support | 2012 |
| Shelton's of London Ltd. | Administrative & support | 2018 |
| Sheridan Court Residents (Newbury) Limited | Households | 1976 |
| Sheridan Strategic Services Limited | Professional & scientific | 2003 |
| Sherlock H Consulting Ltd | Information & communication | 2024 |
| Shields Consulting Limited | Information & communication | 2016 |
| Shinext Ltd | Administrative & support | 2025 |
| Shirley Consultancy Limited | Professional & scientific | 1996 |
| Shirley Hughes Financial Services Ltd | Financial services | 2008 |
| Shoot to Edit Pictures Limited | Professional & scientific | 1999 |
| Shop Thermal Ltd | Wholesale & retail | 2024 |
| Short Creative Ltd | Professional & scientific | 2023 |
| Shorty Delivers Ltd | Transport & logistics | 2025 |
| Shush Creative Limited | Information & communication | 2018 |
| Shush Tech Limited | Professional & scientific | 2025 |
| Shut UP and Work Limited | Professional & scientific | 2015 |
| Sical Ltd | Real estate | 2023 |
| Sidefest Limited | Administrative & support | 2014 |
| Sidwell Computers Limited | Information & communication | 1981 |
| Sierra Blanquilla Holdings Ltd | Financial services | 2021 |
| Sigam Limited | Information & communication | 2012 |
| Signal Atlas Ltd | Information & communication | 2025 |
| Signature Lawn Care Ltd | Administrative & support | 2026 |
| Silver Pearl Foods Ltd | Hospitality | 2024 |
| Silverbox Group Ltd | Arts & recreation | 2021 |
| Silversurfing Limited | Wholesale & retail | 2012 |
| Silvia Campbell Ltd | Manufacturing | 2021 |
| Simms Sweets Ltd | Wholesale & retail | 2025 |
| Simply Lamps Limited | Wholesale & retail | 2008 |
| Simpplr Limited | Information & communication | 2016 |
| Sing Thong 89 Ltd | Hospitality | 2018 |
| Singer Cycles Limited | Extraterritorial | 2024 |
| SIR Digital Limited | Information & communication | 2021 |
| Sirecam (Europe) Limited | Information & communication | 2008 |
| Sirona Solutions Ltd | Wholesale & retail | 2022 |
| Siso Holdings Limited | Professional & scientific | 2015 |
| Sival Hotels Limited | Hospitality | 1986 |
| SIX ST. Julian`S Terrace Management Company Limited | Hospitality | 2007 |
| SJ Construction (Berkshire) Ltd | Construction | 2022 |
| SJ Mackenzie Consulting Ltd | Professional & scientific | 2023 |
| SJB Chef Services Limited | Hospitality | 2010 |
| SJC Power Ltd | Construction | 2021 |
| SJS Tree Services Ltd | Agriculture & fishing | 2025 |
| SK Cumilla Limited | Hospitality | 2024 |
| SK West Bury Limited | Hospitality | 2023 |
| Skaf International Properties Ltd | Real estate | 2016 |
| Skargles Ltd | Hospitality | 2017 |
| Skelect Limited | Manufacturing | 2016 |
| Skills Development 4 U Ltd | Information & communication | 2025 |
| Skincare Online Limited | Wholesale & retail | 2020 |
| Skinners Green Land Company Limited | Extraterritorial | 2012 |
| Skips Electrical Ltd | Construction | 2018 |
| Sky Hawk Films Ltd | Information & communication | 2020 |
| Sky Nails (Gillingham) Limited | Other services | 2016 |
| Skyview Global Limited | Professional & scientific | 2023 |
| SL Beckett Ltd | Professional & scientific | 2023 |
| SL IT Services Ltd | Information & communication | 2008 |
| Slater Veterinary Services Limited | Professional & scientific | 2022 |
| Slattery Roofing Services Ltd | Construction | 2026 |
| Sleep Safe Systems Limited | Manufacturing | 2020 |
| Slorganisation Ltd. | Professional & scientific | 2016 |
| SLV Production Ltd | Information & communication | 2024 |
| SMA Electronics Limited | Manufacturing | 2014 |
| Smart Group Facilities Management Limited | Administrative & support | 2022 |
| Smart Group Services Limited | Administrative & support | 2006 |
| Smart Kids (U.K.) Limited | Administrative & support | 1998 |
| Smart Partners Enterprise Limited | Real estate | 2013 |
| Smart Solutions Limited | Information & communication | 2005 |
| Smashing Blouse Limited | Arts & recreation | 2014 |
| SMC Inspection Services Ltd | Administrative & support | 2019 |
| SME Accounting Services Limited | Professional & scientific | 2008 |
| SME Growth Ltd | Professional & scientific | 2025 |