| Sætheren Element AS | Manufacturing | 2013 |
| Sætheren Holding AS | Real estate | 2005 |
| Sætheren Prosjekt AS | Real estate | 2013 |
| Sætrang AS | | 2023 |
| Sætrang Samdrift Biovarme Da | Energy | 2011 |
| Sætrang Samdrift Da | Agriculture & fishing | 2006 |
| Sætrang Tunet AS | Wholesale & retail | 2025 |
| Söderberg & Partners Ringerike AS | | 2026 |
| Søm AS | Real estate | 2012 |
| Søndre Torv 1 AS | Real estate | 2006 |
| T Og J Hamborg AS | | 2024 |
| T.A Thorsen Holding AS | | 2023 |
| Tailor Holding AS | Wholesale & retail | 2022 |
| Takst Og Kontrollservice AS | Professional & scientific | 2025 |
| Takøy Stasjonsdrift AS | Wholesale & retail | 2026 |
| TALL2V AS | Professional & scientific | 2023 |
| Tannlege Moen AS | Health & social care | 2019 |
| Tannlege Niclas Berggren AS | Health & social care | 2016 |
| Tannlege Niels Krøll AS | Health & social care | 2014 |
| Tannlege Tingleff AS | Health & social care | 2019 |
| Tannlege Tonje K. Eldevik AS | Health & social care | 2015 |
| Tannlegekompaniet AS | Health & social care | 2019 |
| Tannlegene Nohre AS | Health & social care | 2013 |
| Tara Eiendom AS | Real estate | 2003 |
| Taraldsen Elektro AS | Construction | 2025 |
| Tax System AS | Professional & scientific | 2018 |
| Teas Droneflight AS | Information & communication | 2016 |
| Teknometri AS | Financial services | 2012 |
| Tekstbiten AS | Arts & recreation | 2017 |
| Tele-Magasinet Da | Wholesale & retail | 2009 |
| Telegrafalleen 6 AS | Real estate | 2012 |
| Telekiosken Hønefoss AS | Wholesale & retail | 2004 |
| Tenergi AS | Real estate | 2012 |
| Tennar AS | | 2020 |
| Tennisreiser AS | Administrative & support | 2025 |
| Ternmo AS | | 2008 |
| Testa Consulting AS | Administrative & support | 2017 |
| TGK Bygg AS | Construction | 2011 |
| TH Forsikring AS | Financial services | 2013 |
| The Patent Corporation AS | | 1995 |
| Thor Myrvang Gravefirma AS | Construction | 1978 |
| Thoresengården AS | Real estate | 2017 |
| Ti Industrier Hønefoss AS | Manufacturing | 2000 |
| Tidsverk Entreprenør AS | Construction | 2021 |
| Tilia Teien Equiservice AS | Information & communication | 2022 |
| Tingleff Bjørlo AS | Real estate | 2024 |
| Tinus Invest AS | Wholesale & retail | 2005 |
| Tip Top Frisør Ans | Other services | 1989 |
| Tips AS | Wholesale & retail | 2016 |
| Tita Invest AS | Wholesale & retail | 2006 |
| Tj-Produksjon AS | Professional & scientific | 2013 |
| Tjyruhjellen Vannverk SA | Water & waste | 1953 |
| TK Thai & Sushi AS | Hospitality | 2023 |
| TKS Utleie AS | Administrative & support | 2022 |
| Tma Bent AS | Transport & logistics | 2026 |
| Tmkl AS | | 2022 |
| Tn-Solutions AS | Information & communication | 2019 |
| To Be Announced Arrangementer AS | Arts & recreation | 2001 |
| Tofsrudveien 22 AS | Real estate | 2017 |
| Tokt Film AS | Professional & scientific | 2023 |
| Tolpinrud SA | Education | 2004 |
| Tom Y. Lien Consult AS | Health & social care | 2016 |
| Tomco Inspection Ltd Nuf | Professional & scientific | 2006 |
| Toms Fønsterputs I Ørkelljunga Aktiebolage | Administrative & support | 1997 |
| Tony's Matglede AS | Hospitality | 2013 |
| Tonys Restaurant AS | Hospitality | 2023 |
| Tooeasy Norge AS | Wholesale & retail | 2015 |
| Topflight AS | Education | 2004 |
| Tore Bratvold AS | Financial services | 2011 |
| Torger Skaug Spesialtransport AS | Transport & logistics | 2021 |
| Torgersbråten Bolig AS | Real estate | 2012 |
| Torino's Restaurant & Bar AS | Hospitality | 2025 |
| Torjuls Industrimek AS | Manufacturing | 1986 |
| Tornberg Skog Da | Agriculture & fishing | 1956 |
| Torstein Træen AS | Arts & recreation | 2023 |
| Torvgaten Eiendom AS | Real estate | 2011 |
| Tossevika Drift AS | Administrative & support | 2023 |
| Totalisolering AS | Construction | 2015 |
| Toteapp AS | Information & communication | 2024 |
| Toyota Hønefoss AS | Wholesale & retail | 1988 |
| Track Consulting AS | Arts & recreation | 2018 |
| Trafikkskolen Brandenberger AS | Education | 2001 |
| Trans System AS | Transport & logistics | 2025 |
| Tre Og Teknikk AS | Professional & scientific | 2010 |
| Treangen Ved Da | Wholesale & retail | 2023 |
| Tregulvsentralen AS | Construction | 2022 |
| Trehjørningen Invest AS | Real estate | 2006 |
| Trekk Tømmer AS | Transport & logistics | 1988 |
| Treklyngen Industripark AS | Real estate | 2011 |
| Trelyst AS | Professional & scientific | 2014 |
| Tribute Konserter Da | Arts & recreation | 2023 |
| Trio Olje Og Service AS | Wholesale & retail | 2026 |
| Tritonos Gruppen AS | Arts & recreation | 2007 |
| Trollrental AS | Administrative & support | 2015 |
| Trond Berntsen Eiendom AS | Real estate | 2014 |
| Trond Hegseth AS | Education | 2015 |
| Tronds Mur Og Flis AS | Construction | 2014 |
| Tronrud AS | Real estate | 2005 |
| Tronrud Defence AS | Professional & scientific | 2026 |
| Tronrud Eiendom AS | Real estate | 1987 |