| Sijoitusyhtiö Kari Oy | Financial services | 2014 |
| Silicon Fibres Oy | Professional & scientific | 2000 |
| Silltec Oy | Manufacturing | 2024 |
| Silmet Oy | Wholesale & retail | 1981 |
| SimRex Oy | Construction | 2025 |
| Sipi Coaching Oy | Education | 2018 |
| Sirem Oy | Transport & logistics | 2020 |
| Sirius Estates Oy | Real estate | 2026 |
| Sirkjami Oy | Wholesale & retail | 1998 |
| Sirén Holdings Ab | Financial services | 2026 |
| Sisustus Tikka Oy | Construction | 2008 |
| Skandi Incorporated Oy | Wholesale & retail | 2023 |
| Skarppila Konsultointi Oy | Professional & scientific | 2024 |
| Skava-Saneeraus Oy | Construction | 2006 |
| Skyator Oy | Hospitality | 2020 |
| Skynet Group Oy | Construction | 2025 |
| Slashpuul Oy | Wholesale & retail | 1985 |
| Sm peltisepät Oy | Construction | 2023 |
| Smart Pro Engineering Oy | Professional & scientific | 2023 |
| Soap Fair Oy | Wholesale & retail | 2021 |
| Softest Design Oy | Information & communication | 2021 |
| Somest Oy | Wholesale & retail | 1996 |
| Someviidakko Oy | Professional & scientific | 2021 |
| Somia Living Oy | Wholesale & retail | 2004 |
| Soraliike Erik Winqvist Ky | Mining & quarrying | 1981 |
| Sorayhtiö Sjöblom Oy | Construction | 1981 |
| Sormilukko Oy | Education | 2016 |
| Spa Kaiku Oy | Other services | 2025 |
| Spandex Finland Oy | Wholesale & retail | 1995 |
| Sparktek Oy | Construction | 2024 |
| Spe-tek Oy | Construction | 2014 |
| Special Siivous Oy | Administrative & support | 1989 |
| Speed Direct Oy | Manufacturing | 1994 |
| Speed Services Oy | Professional & scientific | 1960 |
| Spindeco Oy | Professional & scientific | 2010 |
| Spinline Investment Oy | Financial services | 2020 |
| Sponsors Mill Oy | Wholesale & retail | 2023 |
| Sports Betting Analyses Hakulinen & Nurkki | Information & communication | 2007 |
| Sprenger Service Oy | Administrative & support | 2016 |
| Square Orange Studios Oy | Manufacturing | 2020 |
| Standout Solutions Oy | Information & communication | 2025 |
| Stella Capital Oy | Financial services | 2014 |
| Steris Europe, Inc. Suomen sivuliike | Manufacturing | 1997 |
| Sterope Solutions Oy | Professional & scientific | 2024 |
| Stirwell Oy | Wholesale & retail | 1998 |
| StoneRoom Oy | Wholesale & retail | 2008 |
| Stonera Oy | Manufacturing | 2024 |
| Storemen Logistics Oy | Transport & logistics | 2005 |
| Strainpro Oy | Professional & scientific | 2015 |
| Strainpro Partners Oy | Administrative & support | 2000 |
| Strax-Konsultointi Oy | Transport & logistics | 1991 |
| Street Grill & Catering Ky | Hospitality | 2015 |
| Studio Halas Oy | Professional & scientific | 1989 |
| Studio Highlight M&S Haanpää Oy | Administrative & support | 2001 |
| Studioviesti Oy | Professional & scientific | 2002 |
| Sujuva Invest Oy | Real estate | 2022 |
| Sulan Katsastus Oy | Professional & scientific | 2014 |
| SuniSa Oy | Real estate | 2008 |
| Sunny Side Up Oy | Professional & scientific | 2019 |
| Sunny Solutions EOOD, Suomen sivuliike | Wholesale & retail | 2018 |
| Suoharju Oy | Real estate | 2012 |
| Suomen Astiapalvelu Oy | Administrative & support | 2017 |
| Suomen Autokaluste Oy | Wholesale & retail | 2005 |
| Suomen Automaalit.net Oy | Wholesale & retail | 2007 |
| Suomen Dieselrakennus Oy SDR | Manufacturing | 1995 |
| Suomen Hallihuolto Oy | Construction | 2026 |
| Suomen Ilmailukauppa Oy | Wholesale & retail | 2012 |
| Suomen Kaapelitiet Oy | Manufacturing | 1985 |
| Suomen Kiinteistöyhtymä Oy | Real estate | 2017 |
| Suomen Konehalli Oy | Manufacturing | 2015 |
| Suomen Konseptikauppa Oy | Professional & scientific | 1993 |
| Suomen Kuljetinhuolto Oy | Manufacturing | 2020 |
| Suomen LVI Verkkokauppa Oy | Wholesale & retail | 2026 |
| Suomen Liikuntasalihuolto Oy | Manufacturing | 2023 |
| Suomen Massalattiat Oy | Construction | 2022 |
| Suomen Matkailuautokeskus Oy | Professional & scientific | 2022 |
| Suomen Nosturimyynti Oy | Wholesale & retail | 2014 |
| Suomen Paalutuspalvelu Oy | Construction | 2024 |
| Suomen Pläkkärit oy | Construction | 2019 |
| Suomen Rakennuslaite-Rent Oy | Construction | 2013 |
| Suomen Rakennuttajatalo Oy | Professional & scientific | 2025 |
| Suomen Rengastukku Oy | Wholesale & retail | 2011 |
| Suomen RuokaHyvä Oy | Wholesale & retail | 2011 |
| Suomen Sinkopuhallus Oy | Construction | 2015 |
| Suomen Sähköturva Oy | Administrative & support | 2009 |
| Suomen Teknohaus Oy | Wholesale & retail | 1987 |
| Suomen Tivoli Oy | Arts & recreation | 1980 |
| Suomen Tulite Oy | Wholesale & retail | 2015 |
| Suomen Tulkkauspalvelu Oy | Professional & scientific | 2022 |
| Suomen V&S Tekniikka Oy | Construction | 2012 |
| Suomen Vannekorjaus Oy | Other services | 2011 |
| Suomen Vaunumesta Oy | Wholesale & retail | 2009 |
| Suomen Vuokramyynti Oy | Real estate | 2022 |
| Suomen pakuhylly Oy | Wholesale & retail | 2010 |
| Suostumus käytännössä Oy | Education | 2026 |
| Supermood Oy | Wholesale & retail | 2021 |
| Supervisoris Oy | Professional & scientific | 2021 |
| Supreme Diner Furniture Oy | Wholesale & retail | 2013 |
| SurfAd Oy | Professional & scientific | 2024 |
| Suujo Oy | Manufacturing | 2026 |