| Sokeritehtaan Ravintolat Oy | Hospitality | 2017 |
| Soleco Ab | Professional & scientific | 1991 |
| Solera Solutions Oy Ab | Real estate | 2021 |
| Soljua Finland Oy | Professional & scientific | 2015 |
| Somaliland Import and Export Ab Oy | Professional & scientific | 2020 |
| Somiska Oy | Health & social care | 2020 |
| Sonck Gruop Oy | Real estate | 2025 |
| Sonicvision Oy | Arts & recreation | 2015 |
| Sorent Oy | Administrative & support | 2022 |
| Sorsapukki Oy | Professional & scientific | 2006 |
| Soulstar Ky | Wholesale & retail | 1992 |
| Souranmaa Invest Oy | Real estate | 2002 |
| South-Haaga Information Trading Corporation Oy | Professional & scientific | 2017 |
| Sovellusmestarit Oy | Professional & scientific | 2008 |
| Speedhooked Oy | Wholesale & retail | 2016 |
| Spiros Group Oy | Professional & scientific | 2022 |
| Springresta Oy | Hospitality | 1994 |
| StanConstruct Oy | Construction | 2023 |
| Starsquad Event Oy | Arts & recreation | 2016 |
| SteamSales Oy | Real estate | 2024 |
| Stenros & Stenros Oy | Hospitality | 2015 |
| Stenvall Invest Oy Ab | Real estate | 2007 |
| Sticks and balls Oy | Hospitality | 2024 |
| Still Unlimited AB | Professional & scientific | 2011 |
| StillArt Ab | Professional & scientific | 2015 |
| Stonevalley Oy | Financial services | 2020 |
| Stoors Ab | Manufacturing | 1979 |
| Storm & Fors Oy | Arts & recreation | 2015 |
| Stringendo Holding Oy | Financial services | 2022 |
| Strömsberg förvaltning Ab | Professional & scientific | 1995 |
| Strömsbergin Mylly Oy | Manufacturing | 1980 |
| Studio Ibelix Oy | Professional & scientific | 2001 |
| Studio Lanzett Oy | Professional & scientific | 2024 |
| Studio Lindell Oy Ab | Wholesale & retail | 1986 |
| Studio Redesign Oy | Professional & scientific | 2025 |
| Studio SK Oy | Information & communication | 2026 |
| Studio WS Oy | Arts & recreation | 2025 |
| Stylea Oy | Professional & scientific | 2008 |
| Sukittajat Ha&Ba Oy | Construction | 2021 |
| Sukitusykköset Oy | Construction | 2018 |
| Sukkakeisari Oy | Water & waste | 2025 |
| Sundi Palvelut Oy | Agriculture & fishing | 2025 |
| Sunspiron Oy | Education | 2010 |
| Sunstorm Oy | Manufacturing | 2018 |
| Sunstorm Trading Oy | Wholesale & retail | 2023 |
| Sunvest Oy | Real estate | 2014 |
| Suomalainen työterveystaito Oy | Health & social care | 1990 |
| Suomen Autopalvelu Yhtiöt Oy | Other services | 2007 |
| Suomen Kioski Oy | Hospitality | 2024 |
| Suomen Kivisora Oy | Manufacturing | 2010 |
| Suomen Kuntotarkastustalo Oy | Professional & scientific | 2024 |
| Suomen Laatusukitus Oy | Construction | 2020 |
| Suomen Lasitehdas Oy | Construction | 1995 |
| Suomen Märkähiekkapuhallus Oy | Construction | 2019 |
| Suomen Paineilma Oy | Wholesale & retail | 2021 |
| Suomen Pelti Oy | Manufacturing | 2021 |
| Suomen Pintatekniikka Oy | Construction | 1996 |
| Suomen Saneeraustarvike Oy | Wholesale & retail | 2012 |
| Suomen Sinkopuhallus Oulu Oy | Construction | 2022 |
| Suomen Sorakivi Oy | Construction | 2026 |
| Suomen Timanttilattiat Oy | Construction | 2021 |
| Suomen Työsuhdepyörä Oy | Administrative & support | 2011 |
| Suomen Yrittäjäin Tilitieto Oy | Professional & scientific | 1991 |
| Suomenkylän Sähkö Oy - Finnby El Ab | Construction | 1994 |
| SupaBright Oy | Information & communication | 2026 |
| Suparex Oy | Real estate | 2014 |
| Supercall Europe Oy | Professional & scientific | 2019 |
| Suppa Oy | Professional & scientific | 2023 |
| Surrexit Cinis Oy | Professional & scientific | 2019 |
| Susa Saukko Productions Oy | Arts & recreation | 2022 |
| Suunnittelurasia Ky | Professional & scientific | 2003 |
| Suursähkö Oy | Construction | 2021 |
| Svart Company Oy | Professional & scientific | 2024 |
| SySari Oy | Hospitality | 2017 |
| Sysx Oy | Information & communication | 2022 |
| Sähkö-Meka Oy | Construction | 2004 |
| Sähköasennukset TM Oy | Construction | 2026 |
| Sähkökuninkaat Oy | Construction | 2023 |
| Sähkömaja Oy | Construction | 2016 |
| Sähköpalvelu J. Heino Oy | Construction | 2018 |
| Sähkövaihe Oy | Construction | 1991 |
| Särmä Sound Oy | Arts & recreation | 2019 |
| Södernäs Oy | Professional & scientific | 2024 |
| Södervik Invest Ab | Administrative & support | 2019 |
| T & M Grand Oy | Hospitality | 2009 |
| T & T Ravintolat Oy | Hospitality | 2014 |
| T&J Holopainen Oy | Wholesale & retail | 2016 |
| T&K Gustafsson Oy | Real estate | 1989 |
| T-tilat Oy | Real estate | 1986 |
| T. Penttilä Oy | Transport & logistics | 1996 |
| T4 Padel Oy | Arts & recreation | 2021 |
| Talousyrittäjät Porvoo OY | Administrative & support | 2021 |
| TBD-Research Oy | Manufacturing | 2024 |
| TCG Rakennus Oy | Construction | 2021 |
| TE3 Oy | Manufacturing | 2016 |
| TEK-Työstö Oy | Manufacturing | 1978 |
| TF-Saneeraus Oy | Construction | 1992 |
| TH Timantti OY | Construction | 2011 |
| TH-kuljetus Ky | Transport & logistics | 1980 |
| Thai Street Food Porvoo OY | Hospitality | 2016 |