| ST. Raphael's Court Management Limited | Households | 1985 |
| STA Property Investments Limited | Real estate | 2025 |
| Stable Court Management Company (ST. Albans) Limited | Households | 1991 |
| Stables Block Ltd | Construction | 2015 |
| Stack Technology Limited | Professional & scientific | 2013 |
| Staddlestone Estates Limited | Real estate | 2021 |
| Staff & Stone CIC | Hospitality | 2025 |
| Staffmate.Io Limited | Information & communication | 2025 |
| Stalion Ltd | Construction | 2018 |
| Stallions Consulting Ltd | Information & communication | 2021 |
| Stamp Creative Limited | Manufacturing | 2006 |
| Stanborough Motors Limited | Real estate | 1961 |
| Stanborough Place Management Company Limited | Households | 2015 |
| Stanbury Court Management Limited | Households | 1996 |
| Stance Orthotics Ltd | Health & social care | 2025 |
| Stand UP Office Limited | Wholesale & retail | 2015 |
| Stanhope Residents Limited | Households | 1996 |
| Stanhope Works Management Limited | Real estate | 1985 |
| Stanley Mill Stroud Ltd | Construction | 2017 |
| Stanmore Electrical Services Ltd | Construction | 2023 |
| Star (Masterpieces) Limited | Real estate | 1961 |
| Star Cleaning Products Ltd | Wholesale & retail | 2012 |
| Star Financial Planning Limited | Financial services | 2002 |
| Star Plant Operative Services and Construction Limited | Construction | 2018 |
| Star Properties (Rugby) Limited | Other services | 2017 |
| Star Sahara Limited | Education | 2025 |
| Star Taxis Travels and Tours Limited | Transport & logistics | 2008 |
| Starav Site Engineering Ltd | Construction | 2015 |
| Starboard Thinking Limited | Professional & scientific | 2015 |
| Starbright Investments Limited | Real estate | 2002 |
| Stargift Properties Limited | Real estate | 2016 |
| Starlight Care Services Ltd | Health & social care | 2019 |
| Starlight Entertainment & Events Ltd | Arts & recreation | 2022 |
| Starline Transport (Herts) Ltd | Transport & logistics | 2025 |
| Starling Tutorial Services Ltd | Education | 2013 |
| Starstruck Marine Capital Ltd | Professional & scientific | 2017 |
| Starting With Red Limited | Administrative & support | 2017 |
| Startpremium Property Management Limited | Households | 1993 |
| Startwise Education Ltd | Education | 2025 |
| STARTWITH3D Ltd | Construction | 2022 |
| State of Agility Ltd | Information & communication | 2019 |
| Station View Dental Practice Limited | Health & social care | 2010 |
| Statistical Consultancy Solutions Ltd | Professional & scientific | 2014 |
| Stay Inn Central Limited | Hospitality | 2019 |
| Staycreationsbyaj Ltd | Hospitality | 2024 |
| Stayova Properties Ltd | Real estate | 2025 |
| STE Projects Limited | Information & communication | 2011 |
| Steamboat Springs Ltd | Professional & scientific | 2015 |
| Steaua Ltd | Other services | 2016 |
| Steel Mate Ltd | Construction | 2025 |
| Stefan Wisniewski Ltd | Wholesale & retail | 2019 |
| Steffi Riley Equestrian Limited | Education | 2020 |
| Stelestial Ltd | Information & communication | 2010 |
| Stella Lange LLP | | 2010 |
| Stellar Developers Ltd | Real estate | 2024 |
| Stellar Equity Consulting Limited | Professional & scientific | 2019 |
| Stellar Strategy Consulting Limited | Professional & scientific | 2023 |
| Stellara Mansion Capital Ltd | Real estate | 2026 |
| Stellata Consulting Ltd | Information & communication | 2022 |
| Stemak Ltd | Wholesale & retail | 2023 |
| Step Learning Limited | Education | 2026 |
| Stepgrowth Ltd | Professional & scientific | 2011 |
| Stephen Baker Consulting Ltd | Professional & scientific | 2016 |
| Stephen Lawrence Limited | Construction | 2007 |
| Stephen MAN Technical Consultancy Ltd | Information & communication | 2013 |
| Stephen Ryan Associates Limited | Financial services | 2010 |
| Stephen Seager Fencing Limited | Construction | 2022 |
| Stepllm Limited | Health & social care | 2016 |
| Stepover Consultancies Limited | Professional & scientific | 2015 |
| Sterex Ltd | Construction | 2021 |
| Sterling Design and Management Limited | Construction | 2017 |
| Sterling Hearth Limited | Construction | 2026 |
| Sterling London Properties Ltd | Real estate | 2023 |
| Sterling Meadow Limited | Real estate | 2023 |
| Sterling Rose Developments Limited | Real estate | 2015 |
| Sterling Sterilisers Ltd | Manufacturing | 2007 |
| Sterlingit Contractors Limited | Information & communication | 2025 |
| Sternblooms Limited | Professional & scientific | 2016 |
| Steve Brown Architecture Limited | Professional & scientific | 2016 |
| Steve Dalton Construction Management Limited | Professional & scientific | 2015 |
| Steve Horne Consultants Limited | Information & communication | 2024 |
| Steven Hale Watch Restorations Limited | Other services | 2005 |
| Stevenson Bell Mortgages Limited | Financial services | 2018 |
| Steverin Ltd | Administrative & support | 2023 |
| Stewart Construction Solutions Limited | Construction | 2025 |
| Sthaa Limited | Information & communication | 2013 |
| Stickman Technology Limited | Extraterritorial | 2003 |
| Stillman Sourced Ltd | Real estate | 2021 |
| Stillwater Group Ltd | Professional & scientific | 2006 |
| Stimpsons Consultant Surveyors Limited | Real estate | 1991 |
| Stipa Transport Ltd | Transport & logistics | 2018 |
| Stirling Butler Limited | Professional & scientific | 2024 |
| Stirling Management Holdings Ltd | Real estate | 2021 |
| Stitched by Ltd | Manufacturing | 2019 |
| STM Appliances Ltd | Other services | 2020 |
| Stokenchurch Property Limited | Professional & scientific | 2016 |
| Stolitsa Limited | Construction | 2024 |
| Stomping Ground Toys Limited | Wholesale & retail | 2019 |
| Stone Town Properties Limited | Real estate | 2023 |
| Stonebell Construction Limited | Real estate | 2012 |