| Tannlegene I Olavsgate AS | Health & social care | 2026 |
| Tannlegene Otterstad AS | Health & social care | 2018 |
| Taxi Cab AS | Transport & logistics | 2024 |
| TB Invest AS | | 2016 |
| TB Systems AS | Construction | 2026 |
| Tba Norge AS | Professional & scientific | 2025 |
| TCM Assets AS | Real estate | 2017 |
| Te-Lønnebakke AS | Real estate | 2012 |
| Team Energy AS | Construction | 2017 |
| Team Saga Invest AS | | 2025 |
| Team Timm AS | | 2022 |
| Teater Avvik AS | Arts & recreation | 2025 |
| Teaterparken AS | Real estate | 2025 |
| Technical CN Ltd | Professional & scientific | 2013 |
| Techniculture Invest AS | Professional & scientific | 2016 |
| Techub AS | Administrative & support | 2019 |
| Ted E Holding AS | | 2019 |
| Teft Industrigulv AS | Construction | 2014 |
| Teigen Invest AS | | 2024 |
| Teka Invest AS | | 2005 |
| Tekk AS | Construction | 2001 |
| Teknikergata 16 AS | Real estate | 2018 |
| Tele Produkter AS | Wholesale & retail | 1990 |
| Tele Produkter Eiendom AS | Real estate | 2005 |
| Tele Trans AS | Transport & logistics | 2004 |
| Telebryggen AS | Manufacturing | 2019 |
| Teleklima AS | Construction | 2006 |
| Telekom Eiendom AS | Real estate | 1995 |
| Telekom Ekspert AS | Construction | 2024 |
| Telemark Byggdrift AS | Construction | 2022 |
| Telemark Byggteam AS | Construction | 2013 |
| Telemark Dekksenter AS | Wholesale & retail | 2003 |
| Telemark Elektrotekniske Tjenester AS | Construction | 2022 |
| Telemark Entreprenør Holding AS | Construction | 2022 |
| Telemark Fjellsprengning AS | Construction | 2021 |
| Telemark Hjertesenter AS | Health & social care | 2017 |
| Telemark Industrigulv AS | Construction | 2019 |
| Telemark Kiropraktorklinikk AS | Health & social care | 2018 |
| Telemark Kjemi AS | Wholesale & retail | 2024 |
| Telemark Lastebil AS | Other services | 1984 |
| Telemark Logistikksenter AS | Real estate | 2016 |
| Telemark Lystbåtformidling AS | Wholesale & retail | 2005 |
| Telemark Pulvelakk AS | Manufacturing | 2024 |
| Telemark Restaurantdrift AS | Hospitality | 2014 |
| Telemark Skadedyrkontroll AS | Administrative & support | 2024 |
| Telemark Skifer- Og Naturstein AS | Mining & quarrying | 2006 |
| Telemark Skilt AS | Manufacturing | 2016 |
| Telemark Solfilm AS | Professional & scientific | 2019 |
| Telemark Spesialistsenter AS | Health & social care | 2025 |
| Telemark Toppidrett Ungdomsskole Porsgrunn AS | Education | 2019 |
| Telemark Urtebrænderi AS | Wholesale & retail | 2008 |
| Telemark Ved AS | Wholesale & retail | 2023 |
| Telemarksgata 7 AS | Real estate | 2005 |
| Telemarksporten Dagligvare AS | Wholesale & retail | 1996 |
| Telerosa AS | Professional & scientific | 2014 |
| Telerør A/S | Construction | 1988 |
| Telerør Eiendom AS | Construction | 2001 |
| Telerør Elektro AS | Construction | 2022 |
| Teleste Norge AS | Wholesale & retail | 1985 |
| Telvest Holding AS | Real estate | 2014 |
| Telvest Utvikling AS | Real estate | 2010 |
| Tenn Sauna AS | Other services | 2025 |
| Teo Invest AS | | 2026 |
| Teoline Holding AS | Financial services | 2013 |
| Teria Consulting AS | Professional & scientific | 2007 |
| Terje Kaasa Holding AS | Financial services | 2017 |
| Terminalbygget Porsgrunn AS | Real estate | 2026 |
| Tes Eiendom AS | Construction | 1989 |
| TG Trading AS | Wholesale & retail | 2021 |
| TGJ Invest AS | Real estate | 2013 |
| TH Tømmerhus AS | Construction | 2019 |
| Thalarctos Analytics AS | Information & communication | 2018 |
| Thalberg Invest AS | Professional & scientific | 2024 |
| The Hills Holding AS | Real estate | 2019 |
| The Living Daylights AS | Arts & recreation | 2026 |
| The Roadkill Da | Arts & recreation | 2012 |
| The Room Porsgrunn AS | Arts & recreation | 2020 |
| Themis Engineering AS | Professional & scientific | 2012 |
| Thim Investments AS | Construction | 2023 |
| Thingstad Eiendom AS | Real estate | 1998 |
| Thingstad Invest AS | | 2020 |
| Thokon AS | Construction | 2010 |
| Thomas F Fredriksen Invest AS | Financial services | 2005 |
| Thor Auto AS | Wholesale & retail | 2025 |
| Til - Huset AS | Wholesale & retail | 2008 |
| Timotei AS | | 1998 |
| Tinholt Bakeri Hovenga AS | Wholesale & retail | 2023 |
| Tipp Frakt AS | Transport & logistics | 2020 |
| Tipp Frakt Holding AS | Transport & logistics | 2019 |
| Tipp Transport AS | Transport & logistics | 1997 |
| Tipp Transport Eiendom AS | Real estate | 2020 |
| Tipp Transport Holding AS | Transport & logistics | 2005 |
| Tippen Barnehage SA | Education | 1988 |
| TJ Interiør AS | Financial services | 2005 |
| Tjenesteleverandøren AS | Agriculture & fishing | 2016 |
| Tjervåg AS | Professional & scientific | 2013 |
| TJG Invest AS | Professional & scientific | 2022 |
| TK Consult AS | Professional & scientific | 2007 |
| TKP Holding AS | Wholesale & retail | 2011 |
| TKT Inneklima AS | Construction | 2019 |