| Oy Sun Pictures Ltd | Information & communication | 2005 |
| Oy Sungam Ab | Information & communication | 1977 |
| Oy Suomalaisia Arvopapereita - Finska Värdepapper Ab | Financial services | 1932 |
| Oy Suomen Puhelinlääkäri - Finlands Telefonläkare Ab | Health & social care | 1989 |
| Oy Suomen Taksivälitys - Taxi Finland Ltd | Transport & logistics | 2016 |
| Oy Suomen Tietokehitys ab | Information & communication | 1983 |
| Oy Suomu-Gratus Ab | Professional & scientific | 1990 |
| Oy Suorahakutoimisto ISPA Finland Ab | Professional & scientific | 2018 |
| Oy Svinön Saaristokauppa - Svinö Skärgårdsbutik Ab | Wholesale & retail | 2012 |
| Oy Swegon Ab | Wholesale & retail | 1976 |
| Oy Sähkökvartti - Elkvarten Ab | Construction | 1983 |
| Oy Sävasund Byggtjänst Ab | Construction | 1996 |
| Oy TIP-Team Ab | Professional & scientific | 1994 |
| Oy TNT Kiinteistöt Ab | Real estate | 2025 |
| Oy TNT-Putki Ab | Construction | 2005 |
| Oy TQM Consultants Ltd. | Professional & scientific | 1991 |
| Oy Taxi-Service Kerstin Puustinen Ab | Transport & logistics | 1999 |
| Oy Tech Know Ltd | Health & social care | 1989 |
| Oy Tecmaster Ab | Construction | 1997 |
| Oy Tekno-Marine Ab | Wholesale & retail | 1990 |
| Oy Telpak Ab | Wholesale & retail | 2008 |
| Oy Teollisuuskiinteistö Maasilta Ab | Wholesale & retail | 1992 |
| Oy Tersil Ab | Real estate | 1989 |
| Oy Tertrade Ab | Real estate | 1989 |
| Oy Terveys Sinun Tiimi | Health & social care | 2024 |
| Oy Thindime Ab | Real estate | 1995 |
| Oy Thyella Capital Ab | Financial services | 2021 |
| Oy Tilion Ab | Professional & scientific | 1984 |
| Oy Tiller Ab | Wholesale & retail | 1965 |
| Oy Tiralex Ab | Wholesale & retail | 1990 |
| Oy Titoki Ab | Financial services | 1984 |
| Oy Tomtebo Ab | Financial services | 2004 |
| Oy Ton-Art Ab | Arts & recreation | 1987 |
| Oy Top Brands Ab | Wholesale & retail | 1995 |
| Oy Toppi Ab | Manufacturing | 1975 |
| Oy Torch Engineering Ltd | Professional & scientific | 1996 |
| Oy TradeHuset AB | Professional & scientific | 2020 |
| Oy Transaurus Ab | Professional & scientific | 1993 |
| Oy Transmeri Ab | Wholesale & retail | 2013 |
| Oy Transmeri Group Ab | Wholesale & retail | 1928 |
| Oy Trexet Finland Ab | Wholesale & retail | 1992 |
| Oy Truck Colours Finland Ab | Other services | 1996 |
| Oy Unilink Ab | Wholesale & retail | 1984 |
| Oy United Europe Trading Ltd | Wholesale & retail | 1990 |
| Oy Vaahteranoksa Ab | Professional & scientific | 2024 |
| Oy Vacilando Ab | Financial services | 1989 |
| Oy Varex Imaging Finland Ltd. | Manufacturing | 2001 |
| Oy Vargas Mora Ltd | Professional & scientific | 2005 |
| Oy Vassbuk Capital Ab | Financial services | 2015 |
| Oy Veblen Glazer Ab | Professional & scientific | 2010 |
| Oy Velipentit Ab | Wholesale & retail | 2023 |
| Oy Veljekset Juslin Ab | Administrative & support | 2012 |
| Oy Veneparkki Svartbäck Ab | Transport & logistics | 2005 |
| Oy Vermco Ltd | Education | 1989 |
| Oy Vertika International Ltd | Real estate | 1995 |
| Oy Vestek Ab | Wholesale & retail | 2022 |
| Oy Vida Boa Ab | Administrative & support | 2019 |
| Oy ViherKeskinen Ab | Professional & scientific | 2009 |
| Oy WL Consulting Ltd | Professional & scientific | 2015 |
| Oy Wahlberg Capital Ab | Financial services | 2021 |
| Oy Wavelax Ltd | Real estate | 1989 |
| Oy WestCraft Ab | Construction | 2010 |
| Oy Westerholm Consulting Ab | Real estate | 2016 |
| Oy Wilfa Suomi Ab | Wholesale & retail | 1981 |
| Oy Wilnorr Ltd | Professional & scientific | 2003 |
| Oy Wiztivi Gaming Ltd | Wholesale & retail | 2016 |
| Oy Y. Korteniemi Ab | Construction | 1958 |
| Oy Ylläksen Latu ja Piikki, Ylläs Spår och Pik Ab | Real estate | 1983 |
| Oy iRony Ltd | Professional & scientific | 1993 |
| Oy lørdagshop Ab | Wholesale & retail | 2019 |
| Oy of Despair | Arts & recreation | 2025 |
| Oy Öuddtorp Ab | Real estate | 1995 |
| Oy.Kuntola | Real estate | 1942 |
| P & A International Travel OY LTD | Administrative & support | 2021 |
| P & P Enterprise Oy | Hospitality | 2023 |
| P&L Management Oy | Professional & scientific | 2019 |
| P-Holding 2017 Oy | Financial services | 2020 |
| P-Loitsu Oy | Real estate | 2024 |
| P-store Oy | Wholesale & retail | 2007 |
| P. F. F. Group Oy | Hospitality | 2016 |
| P. Juha Dental Service Oy | Health & social care | 2023 |
| P. Lindfors Engineering Oy | Professional & scientific | 2007 |
| P. Paju Oy | Health & social care | 2025 |
| P. Tyllilä Linja Oy | Transport & logistics | 1995 |
| P. Vorimo Ky | Professional & scientific | 1976 |
| P.C. Wik Holding Ab | Financial services | 1996 |
| P.I.M.B. Oy | Other services | 2021 |
| P.L.Servicios oy | Professional & scientific | 2026 |
| P.O.B.-Tech Oy | Manufacturing | 1991 |
| P.S. Wahlberg Oy | Professional & scientific | 2020 |
| P2P Sales Partners Oy | Administrative & support | 2012 |
| P2PGoods Oy | Wholesale & retail | 2024 |
| P2X Joensuu Oy | Manufacturing | 2025 |
| P2X Solutions Oy | Manufacturing | 2020 |
| P2rt-rak Oy | Construction | 2018 |
| P2rt-rakennus oy | Construction | 2022 |
| PA Sijoitus Oy | Financial services | 2021 |
| PA Ventures Oy | Financial services | 2024 |
| PAC solutions Oy | Administrative & support | 2021 |
| PACE Sport OY | Arts & recreation | 2016 |