| Smith & Holroyd Properties Limited | Extraterritorial | 2021 |
| Smith Works Ltd | Professional & scientific | 2024 |
| Smithmore Properties Limited | Real estate | 2020 |
| Smiths Investments Ltd | Real estate | 2015 |
| Smiths Stratford Limited | Real estate | 2022 |
| Smithson Properties Limited | Real estate | 2003 |
| Smithsons Jewellers Limited | Wholesale & retail | 1976 |
| SMP GAS & Heating Ltd | Construction | 2019 |
| Snagged Building Services Ltd | Construction | 2022 |
| Snee Brothers Carpets and Flooring Ltd | Construction | 2020 |
| Snipz (LB) Limited | Other services | 2013 |
| Snjnorton Limited | Real estate | 2017 |
| SNN 2021 Ltd | Construction | 2021 |
| Snomedix Ltd | Health & social care | 2025 |
| SO Lovely Limited | Wholesale & retail | 2025 |
| Social Media Strategist Limited | Information & communication | 2010 |
| Socially Co. Ltd | Professional & scientific | 2025 |
| Socialworld Limited | Wholesale & retail | 1998 |
| Sohara Legal Consultancy Limited | Professional & scientific | 2019 |
| SOL Network Ltd | Wholesale & retail | 2026 |
| Sola Productions Limited | Information & communication | 2022 |
| Solaar Ltd | Wholesale & retail | 2023 |
| Solo Installation Services Ltd | Wholesale & retail | 2006 |
| Solution International Limited | Wholesale & retail | 2007 |
| Sonia's Illustrations Limited | Arts & recreation | 2025 |
| Soper & Co Trading Ltd | Wholesale & retail | 2022 |
| Sophia LA Porta Ltd | Arts & recreation | 2019 |
| Sopra Engineering Limited | Information & communication | 2018 |
| Sorelli Limited | Hospitality | 2016 |
| Sors Consulting Ltd | Professional & scientific | 2009 |
| Sorteo Ltd | Information & communication | 2025 |
| SOS Planet Earth Ltd | Wholesale & retail | 2008 |
| Soulbury Enterprises Limited | Professional & scientific | 1998 |
| Soulbury Management Services Limited | Administrative & support | 2016 |
| Sound Booth Installs Ltd | Construction | 2008 |
| South Hams Rentals Ltd | Extraterritorial | 2023 |
| South Side Studios CIC | Arts & recreation | 2023 |
| Southcott Solutions Limited | Professional & scientific | 2022 |
| Southorn Consulting Ltd | Professional & scientific | 2024 |
| Southside Consulting Limited | Information & communication | 1998 |
| Sovereign Beeches (Farnham Common) Management Company Limited | Households | 1998 |
| Sovereign Court (Aylesbury) Management Limited | Households | 1991 |
| Sovereign Lettings Ltd | Real estate | 2025 |
| Soyou Boutique Limited | Wholesale & retail | 2014 |
| Space Maker Ltd | Real estate | 2026 |
| Spacebar Films Ltd | Administrative & support | 2024 |
| Spacebot Interactive Ltd | Information & communication | 2020 |
| Spaceprove Ltd | Construction | 2019 |
| Spark Valley Limited | Professional & scientific | 2015 |
| Spartan Power Services Ltd | Other services | 2020 |
| SPC Heating & GAS Limited | Construction | 2018 |
| Speak Data and Compliance Ltd | Professional & scientific | 2019 |
| Special Domestic Kleen Services Limited | Professional & scientific | 2020 |
| Specialised Imaging Limited | Manufacturing | 2004 |
| Specialist Ground Engineering Limited | Construction | 2014 |
| Specta Property Ltd | Real estate | 2024 |
| Spectrum (Newport Pagnell) Management Limited | Households | 2007 |
| Spectrum Community Arts Limited | Arts & recreation | 2019 |
| Speed Motors Corner Ltd | Wholesale & retail | 2018 |
| Speers Consulting Limited | Professional & scientific | 2026 |
| Spellbound Residences Limited | Real estate | 2025 |
| Spelman Developments Ltd | Construction | 2007 |
| Spelman Limited | Construction | 2010 |
| Spgonlinetrading Limited | Wholesale & retail | 2023 |
| Spice Lounge Leighton Ltd | Hospitality | 2025 |
| Spicer Business Consultancy Limited | Professional & scientific | 2023 |
| Spicers Yard Haddenham Management Limited | Households | 2011 |
| Spiral Portfolio Limited | Real estate | 2003 |
| Sports Fame & ENT Limited | Education | 2025 |
| Spotless Group Ltd | Administrative & support | 2024 |
| Spraggon Consultancy Limited | Professional & scientific | 2026 |
| Spray Investments (UK) Limited | Real estate | 2003 |
| Spread Software Ltd | Information & communication | 2025 |
| Springfield Court (Linslade 1990) Limited | Real estate | 1990 |
| Sqbnd Ltd | Wholesale & retail | 2025 |
| Squilville Limited | Arts & recreation | 2024 |
| Sqwyz Limited | Professional & scientific | 2019 |
| Srathore Limited | Hospitality | 2024 |
| SS Supplier Ltd | Wholesale & retail | 2024 |
| SSJ Film Craft Limited | Construction | 2022 |
| Ssws Construction Ltd | Construction | 2024 |
| ST Carpentry Services Limited | Construction | 2015 |
| ST George's Place (Ampthill) Management Company Limited | Households | 2016 |
| ST James Gate (Manager Land) Limited | Extraterritorial | 2021 |
| ST Mary's Place (Aylesbury) Management Company Limited | Households | 2001 |
| St.Faith Development Limited | Construction | 2005 |
| Stag Lane (Berkhamsted) Management Company Limited | Households | 2007 |
| Stage Star Studios Ltd | Arts & recreation | 2021 |
| Staines Upon Thames Tanning Ltd | Other services | 2021 |
| Stan Collins & Co Ltd | Professional & scientific | 2015 |
| Stanbridge Homes Limited | Real estate | 1984 |
| Stanbridge Leisure Limited | Arts & recreation | 1992 |
| Stangate HR Ltd | Administrative & support | 2014 |
| Stangate Recruit Limited | Administrative & support | 2023 |
| Stanley Hattersley Property Limited | Real estate | 2014 |
| Stanrite Limited | Health & social care | 2016 |
| Stansfield Auto Electrical Services Limited | Manufacturing | 1978 |
| Stanton Catering Services Ltd | Hospitality | 2026 |
| Stanton Valley Foods Limited | Administrative & support | 2013 |
| Star Construction Management Limited | Construction | 2016 |