| Ti Copil AS | Wholesale & retail | 2017 |
| Tico Mectronics AS | Professional & scientific | 2006 |
| Tk-Invest AS | Real estate | 2005 |
| TNB Askim AS | Wholesale & retail | 2026 |
| To Farger AS | Construction | 2022 |
| Tommy AS | | 2020 |
| Tomter Eiendomsdrift AS | Real estate | 2014 |
| Tomter Sentrum Utvikling AS | Real estate | 2022 |
| Tone S. Agentur AS | Wholesale & retail | 2018 |
| Torget Legesenter Askim Da | Health & social care | 2014 |
| Torget Tandoori AS | Hospitality | 2022 |
| Tornerud AS | Construction | 2024 |
| Torvet Eiendom Ans | | 1992 |
| Torvet Eiendom AS | Real estate | 2006 |
| Toverud Holding AS | Real estate | 2012 |
| Trendsport AS | Wholesale & retail | 2021 |
| Tresox AS | | 2021 |
| Trio Import Og Salg Ans | Wholesale & retail | 2002 |
| Trippeldrift AS | Construction | 2026 |
| Trippestad Holding AS | Real estate | 2010 |
| Trippestad Tennis SA | Administrative & support | 2020 |
| Trippestadveien AS | Real estate | 2020 |
| Trippestadåsen Garasjelag SA | Real estate | 2018 |
| Troll Outdoor AS | Administrative & support | 2023 |
| Trolo AS | Professional & scientific | 2008 |
| Trolo Holding AS | | 2022 |
| Trøgstadveien 13 AS | Real estate | 1998 |
| Trøgstadveien Næringspark AS | Real estate | 2009 |
| Trømborg Ventilasjonspartnere AS | Construction | 2006 |
| Tse A/S | Health & social care | 1988 |
| TTC Eiendom AS | Manufacturing | 1985 |
| TTC Invest AS | Real estate | 2021 |
| TTC Prosjekt AS | Real estate | 2017 |
| Ttth AS | Wholesale & retail | 2021 |
| Tunnelsyn AS | | 2015 |
| Turulia Eiendom AS | Real estate | 2015 |
| TVP Eiendom AS | Real estate | 2002 |
| Tyren Holding AS | Construction | 2005 |
| Tømrer- Og Snekkertjeneste AS | Construction | 2021 |
| Uca Holding AS | | 2021 |
| Ullfrotte Original AS | Wholesale & retail | 2020 |
| Umca Holding AS | Real estate | 2020 |
| Urban Invest AS | Real estate | 2010 |
| Urbanski Invest AS | Real estate | 2021 |
| Utviklingsselskapet Myra Tebo AS | Real estate | 2014 |
| Utviklingsselskapet Sylvia AS | Information & communication | 2024 |
| Vab Arkitekter AS | Professional & scientific | 2021 |
| Vario Sport AS | Wholesale & retail | 2004 |
| Vendu AS | Information & communication | 2016 |
| Venner AS | Other services | 2011 |
| Ventilasjonstjenesten AS | Construction | 2021 |
| Very Tasty Holding AS | Information & communication | 2023 |
| Veske Compagniet AS | Wholesale & retail | 2013 |
| Veslebu AS | Real estate | 2005 |
| Vestre Ringvei 16 AS | Real estate | 2010 |
| Vestre Ringvei 5 AS | Real estate | 2010 |
| VIA3 AS | Health & social care | 1990 |
| Vibelife AS | Information & communication | 2022 |
| Vidar Østre AS | Administrative & support | 2000 |
| Vidars Autorep AS | Other services | 1987 |
| Viken Gummiservice AS | Wholesale & retail | 2020 |
| Viking Kvartalet AS | Real estate | 2014 |
| Vip Taxi AS | Transport & logistics | 2025 |
| Vittorella AS | Professional & scientific | 2004 |
| VM Service & Vedlikehold AS | Manufacturing | 2025 |
| Vo Klima AS | Construction | 2022 |
| Vågmo & Ruud Music & Entertainment Ans | Arts & recreation | 1998 |
| Wax on Bilvask AS | Other services | 2024 |
| Westgaard VVS AS | Construction | 2021 |
| Westli Mur & Flis AS | Construction | 2026 |
| Willy Olsen El Installasjon AS | Construction | 2012 |
| Wingbyh Invest AS | Administrative & support | 2009 |
| Witre Invest AS | | 2023 |
| Xdesign Ans | Information & communication | 2001 |
| XS Holding AS | Real estate | 1988 |
| Yellow Flower AS | Manufacturing | 2011 |
| Ynolens AS | Manufacturing | 2011 |
| Zachrisson Service AB | Manufacturing | 2009 |
| Zi Holding AS | Construction | 2016 |
| Zink AS | Professional & scientific | 2014 |
| Åkerhaugen Da | Agriculture & fishing | 2025 |
| Åttans Bygg AB | Wholesale & retail | 2014 |
| Æsop AS | Real estate | 2006 |
| Ødegård Og Østby AS | Professional & scientific | 1988 |
| Økm Eiendom AS | Real estate | 2022 |
| Økm Holding AS | Construction | 2022 |
| Økne Service AB | Manufacturing | 2009 |
| Øst Holding AS | Professional & scientific | 2018 |
| Østfold Bilauksjon AS | Wholesale & retail | 1984 |
| Østfold Bilformidling AS | Real estate | 2012 |
| Østfold Kuldemontasje AS | Construction | 2024 |
| Østfold Miljøteknikk AS | Construction | 2012 |
| Østfold Næringspark AS | Real estate | 2000 |
| Østfold Service Og Vedlikehold AS | Administrative & support | 2022 |
| Østre Linje Arkitektur Og Landskap AS | Professional & scientific | 2020 |
| Østfold Trykkeri AS | Manufacturing | 1987 |