| Sommerro Invest AS | Real estate | 2006 |
| Sparepartner Investeringsrådgivning AS | Professional & scientific | 2007 |
| Sparring AS | Real estate | 2023 |
| Spesialprodukter Øst Da | Manufacturing | 2004 |
| Spine Rescue AS | Professional & scientific | 2018 |
| Sporpind Utbygningsselskap AS | Construction | 1980 |
| Spruce Holding AS | Financial services | 2005 |
| ST Mariegt 57 AS | Real estate | 1968 |
| Staff AS | Arts & recreation | 2006 |
| Staff Capital Management AS | Arts & recreation | 2023 |
| Stall Tonheim AS | Education | 2016 |
| Starina AS | Wholesale & retail | 1993 |
| Steinar Larsen Anleggsgartneri AS | Administrative & support | 2014 |
| Stensvik Og Bastevikens Vann Og Avløp SA | Water & waste | 2003 |
| Stensvikfjellet Vann Og Avløp AS | Water & waste | 2024 |
| Stian Johannessen Holding AS | | 2025 |
| Stian Johnsen Invest AS | | 2019 |
| Stine Fayes Eiendom AS | Real estate | 2016 |
| Stokmarknes Datasenter AS | Real estate | 2021 |
| Stomatologica AS | Health & social care | 2019 |
| Storken Eiendom AS | Real estate | 2010 |
| Storli Nordic Holding AS | Professional & scientific | 2016 |
| Storm Elektro AS | Construction | 2019 |
| Storveien 3B AS | Real estate | 2025 |
| Storveien 94-96 AS | Real estate | 2023 |
| Storveien Eiendom AS | Real estate | 1994 |
| Storveien Eiendom Drift AS | Hospitality | 2002 |
| Storvola AS | Professional & scientific | 2008 |
| Strand Bolig & Eiendom AS | Real estate | 2021 |
| Strand Investering AS | Professional & scientific | 2022 |
| Stranda Marina AS | Transport & logistics | 2007 |
| Strandbakken Holding AS | Wholesale & retail | 2022 |
| Studio B1T AS | Professional & scientific | 2018 |
| Subseapilot Nuf | Professional & scientific | 2024 |
| Sus Eiendomsutvikling AS | Real estate | 2022 |
| Sus Holding AS | Real estate | 2022 |
| SVG Da | Agriculture & fishing | 2008 |
| Sydøst Marine AS | Wholesale & retail | 2021 |
| Sykkelforlaget AS | Information & communication | 2013 |
| Søndre Hankø Va SA | Water & waste | 2009 |
| T H Christiansen Maskin Og Verktøyindustri AS | Manufacturing | 1995 |
| T. Johansen Invest AS | | 2025 |
| Ta Drift & Eiendom AS | Real estate | 2024 |
| Ta Eiendom & Hytteservice Da | Administrative & support | 2023 |
| Takstpartner Østfold AS | Real estate | 2025 |
| Talseth AS | | 2026 |
| Tangen Utredning Og Consulting AS | Professional & scientific | 2025 |
| Tasty Co. AS | Hospitality | 2024 |
| TB Rep Og Service AS | Wholesale & retail | 1991 |
| Te-Ma AS | Real estate | 2020 |
| Tecon AS | Wholesale & retail | 1992 |
| Teigland Gruppen AS | Professional & scientific | 2017 |
| Tel-Rad AS | Wholesale & retail | 1971 |
| Terje Bøckmann AS | Financial services | 2013 |
| TG Utvikling AS | Real estate | 2015 |
| The Souvereign Order of the Orthodox Knights Hospitaller of Saint John of Jerusalem | Health & social care | 2002 |
| Thelen AS | Education | 2005 |
| Thunderbolt AS | Wholesale & retail | 2023 |
| Tight Lines Holding AS | | 2025 |
| Tilvelforma AS | Information & communication | 2012 |
| Timeyouright AS | Information & communication | 2020 |
| TK Bil AS | Other services | 2009 |
| TK Maskindrift AS | Construction | 2016 |
| TK Maskindrift Eiendom AS | Administrative & support | 2026 |
| TM Svensson Holding AS | Hospitality | 2025 |
| Tma Holding AS | Real estate | 2005 |
| To-Mo Modeller & Interiør AS | Manufacturing | 1984 |
| Toce Invest AS | Health & social care | 2006 |
| Tom Langgård AS | Wholesale & retail | 1987 |
| Tonheim Media AS | Professional & scientific | 2025 |
| Torgersen Rørleggerservice AS | Construction | 2023 |
| Torgets Lille Kjøkken AS | Hospitality | 2004 |
| Tormod Skolt AS | Financial services | 2006 |
| Torvbanen 11 AS | Real estate | 2021 |
| Torvik Trailerrep AS | Other services | 2012 |
| TPX Eiendom AS | Real estate | 2016 |
| Trebygg Norge AS | Construction | 2016 |
| Trilikri AS | Wholesale & retail | 2024 |
| Trolltun Invest AS | Real estate | 2002 |
| Trond Karlsen AS | | 2007 |
| Trondalen Barnehage AS | Education | 2022 |
| Truck Agent Østfold AS | Manufacturing | 2025 |
| Trukol Holding AS | | 2026 |
| Truls Østerud AS | Wholesale & retail | 2020 |
| Trygg Bil AS | Wholesale & retail | 2023 |
| Trygg Bil Holding AS | | 2023 |
| Tstu Invest AS | | 2025 |
| Ttorp Drift AS | | 2024 |
| Ttorp Holding AS | | 2024 |
| Tukkensæter AS | | 2021 |
| Tvete Invest AS | Financial services | 2017 |
| Tømrer Tobias Knudsen AS | Construction | 2022 |
| Tømrerfirma David Svensen AS | Construction | 2010 |
| Tømrerfirmaet Jaaks AS | Construction | 2012 |
| Tømrergutta Drift AS | Construction | 2019 |
| Tønnesen Mur & Flis AS | Construction | 2023 |
| Unneberg Frisør AS | Other services | 2025 |
| Utleie Og Eiendom AS | Real estate | 1998 |
| Utvær Holding AS | Construction | 2022 |
| V. Huth Holding AS | | 2025 |