| TB Indrivningsbolag AS | Administrative & support | 2016 |
| Tb-Eiendom AS | Real estate | 2013 |
| TBB Gruppen AS | Financial services | 2002 |
| Tbe Invest AS | | 2025 |
| Tchem AS | Wholesale & retail | 2019 |
| TD Bygg Service AS | Construction | 2013 |
| Teatergata 1 AS | Real estate | 2021 |
| Teatergata 2 AS | Real estate | 2021 |
| Teatergata 37 AS | | 2022 |
| Tecap Management AS | Wholesale & retail | 2016 |
| Techmarin Solutions AS | Wholesale & retail | 2016 |
| Techpro AS | Wholesale & retail | 2018 |
| Techsub AS | Professional & scientific | 2013 |
| Teddy Boy AS | Other services | 2018 |
| Teien AS | Real estate | 2005 |
| Tekfom AS | Information & communication | 2021 |
| Telekiosken Lillestrøm AS | Wholesale & retail | 2002 |
| Televeien 2 Holding AS | Real estate | 2023 |
| Telko Norway AS | Wholesale & retail | 2008 |
| Terje Skjølberg AS | | 2021 |
| Terra Watches by Explorers AS | Wholesale & retail | 2022 |
| TG Investment AS | Real estate | 2013 |
| TGZ AS | | 2021 |
| The Aviation Factory Norway AS | Transport & logistics | 2025 |
| The Barbecue AS | Hospitality | 2018 |
| The Catering AS | Wholesale & retail | 2021 |
| The Northern Lights AS | Health & social care | 2001 |
| Thea Fossum Skjølberg AS | | 2021 |
| Thegra Holding AS | | 2023 |
| Themikris Holding AS | Information & communication | 2019 |
| Thomas Solbjør AS | Financial services | 2017 |
| Thomle Invest AS | | 2020 |
| Thor Nordahl AS | Financial services | 2005 |
| Thors Hage AS | Real estate | 2019 |
| Thorvald Lammers' Gate 2 Og 8 AS | Real estate | 2016 |
| Thrana Academy AS | Information & communication | 2022 |
| Thress AS | Agriculture & fishing | 1997 |
| Thru Drift AS | Professional & scientific | 2025 |
| Thy Frisør Lillestrøm AS | Other services | 2024 |
| Thy Frisør Og Systua AS | Other services | 2018 |
| Tianlong AS | Financial services | 2016 |
| Time Holding AS | Wholesale & retail | 2017 |
| Tims Burger AS | Hospitality | 2015 |
| Tims Burger&Bar AS | Hospitality | 2017 |
| Tiny Workers AS | Professional & scientific | 2021 |
| Tiq AS | Real estate | 2015 |
| Tiq Regnskap AS | Professional & scientific | 2017 |
| Tiq Regnskapsbyrå AS | Professional & scientific | 2013 |
| Titan Equity Fund | | 2016 |
| Tjongsfjord Invest AS | Real estate | 2008 |
| TKP Technology Holding AS | | 2023 |
| Tla Holding AS | Financial services | 2008 |
| Toftesgate 15A Og 19B AS | Real estate | 2016 |
| Toja Ans | Real estate | 1969 |
| Toja Regnskap AS | Professional & scientific | 1991 |
| Toka AS | Real estate | 2021 |
| Toma Logistikk AS | Transport & logistics | 2025 |
| Tomina Frisør AS | Other services | 2001 |
| Tommy Holding AS | | 2019 |
| Tomteselskapet Romerike AS | Real estate | 2009 |
| Tony Bjuhr | Construction | 2003 |
| Tony Christensen AS | Real estate | 2013 |
| Topp Eiendomsdrift AS | Administrative & support | 2023 |
| Toptemp Romerike AS | Administrative & support | 2004 |
| Torget 28 AS | Real estate | 2021 |
| Torget Legesenter AS | Health & social care | 2022 |
| Torggt 25 Holding AS | Real estate | 2023 |
| Torggt 25 Næring AS | Real estate | 2023 |
| Tormod Tømte AS | Real estate | 1998 |
| Torrob AS | Wholesale & retail | 2005 |
| Torvet Øst Lillestrøm AS | Real estate | 1998 |
| Torvgata 11A Eiendom AS | | 2025 |
| Torvgata 11C Eiendom AS | Real estate | 2025 |
| Tosterud Holding AS | Real estate | 2005 |
| Total Recovery AS | Health & social care | 2026 |
| Totalfiks AS | Construction | 2026 |
| Totalprosjekt AS | Real estate | 1978 |
| Trailerservice AS | Other services | 2011 |
| Trallabom AS | Professional & scientific | 2021 |
| Tran Group Holding AS | Wholesale & retail | 2017 |
| Transfjell AS | Transport & logistics | 2022 |
| Travision AS | Wholesale & retail | 2016 |
| Trehusgruppen AS | Professional & scientific | 2005 |
| Trendy Eiendom AS | Real estate | 2016 |
| Trendy Næringseiendommer AS | Real estate | 2018 |
| TRG Service AS | Administrative & support | 2017 |
| Triventura AS | Professional & scientific | 2021 |
| Trivselsleder AS | Education | 2010 |
| Troda AS | Professional & scientific | 1998 |
| Trond Westbye AS | Administrative & support | 2023 |
| Trondheimsvegen 74 Holding AS | Real estate | 2025 |
| Trondheimsvegen 74 Næring AS | | 2025 |
| Trondheimsvegen 83 AS | Real estate | 2007 |
| Trondheimsveien 114 Skedsmo AS | Real estate | 1995 |
| Tross Norge AS | Professional & scientific | 2018 |
| Trunk AS | Information & communication | 2005 |
| Trygderettsadvokat Inga S. Kjernlie AS | Professional & scientific | 2021 |
| Trygg Trafikkskole AS Avd Romerike | Education | 2018 |
| Tryggmed Psykiatri AS | Health & social care | 2026 |
| Tryllemann Eiendom AS | Real estate | 2014 |