| Storgata 11 Rakkestad AS | Real estate | 2015 |
| Storgaten 3 AS | Real estate | 2019 |
| Storgaten 40 Mysen AS | Real estate | 2005 |
| Strahltec AS | Construction | 2016 |
| Strahltec Eiendom AS | Real estate | 2021 |
| Strahltec Holding AS | Agriculture & fishing | 2016 |
| Streit Sagt AS | Professional & scientific | 2013 |
| Studio Rod Bianco AS | Wholesale & retail | 2011 |
| Sue AS | Arts & recreation | 2023 |
| Sulland Indre Østfold AS | Wholesale & retail | 2004 |
| Svein Erik Lund AS | Agriculture & fishing | 2020 |
| Svendsen Profil AS | Manufacturing | 2020 |
| Sydlegene AS | Real estate | 2002 |
| SYSTEMBYGG1 AS | Construction | 2021 |
| Sætra Og Vølen Vei SA | Other services | 2001 |
| Sørby Trafikk-Skole AS | Education | 2012 |
| Søvnklinikken AS | Health & social care | 2012 |
| Tangen Lyd Og Lys AS | Arts & recreation | 2008 |
| Tannlege Larsen AS | Health & social care | 1990 |
| Tape Tres Music AS | Information & communication | 2024 |
| Taunus AS | Real estate | 2005 |
| Teamkraft Sør AS | Professional & scientific | 1991 |
| Teien Eiendom AS | Real estate | 2000 |
| Terje Bergstrøm AS | Administrative & support | 2019 |
| Tgø Tilhenger AS | Wholesale & retail | 2020 |
| Thea Morgan T M Eiendom Ans | Real estate | 2001 |
| Thermosaver AS | Manufacturing | 2019 |
| Thorleif Erik Faureng AS | | 2020 |
| Tip Teknologi I Praksis AS | Information & communication | 1997 |
| Tojo Holding AS | Real estate | 2022 |
| Tone Johnsrud Holding AS | | 2024 |
| Tor Jota Treprodukter Ans | Manufacturing | 2022 |
| Tor Ove Solberg AS | Health & social care | 2005 |
| Torbjørn Undeland Holding AS | Information & communication | 2020 |
| Torggata 2 Mysen AS | Real estate | 2019 |
| Torggaten 20 AS | Real estate | 2015 |
| Torp Regnskap AS | Professional & scientific | 1995 |
| Torperåsen AS | Real estate | 2019 |
| Torperåsen Vann- Og Avløpslag SA | Real estate | 2018 |
| Trailer Solution AS | Other services | 2023 |
| Tre Kloss Majoren AS | | 2023 |
| Tre Tommer AS | Construction | 2020 |
| Tre Tommer Holding AS | Construction | 2021 |
| Trond Prests Vei AS | Real estate | 2015 |
| Truls Tvete AS | Professional & scientific | 2025 |
| Trøgstad Eiendom AS | Real estate | 2004 |
| Trømborg Skog AS | Agriculture & fishing | 2016 |
| Trømborg-Treprodukter AS | Wholesale & retail | 2026 |
| Tuvid AS | | 2021 |
| Tøa Invest AS | Real estate | 2008 |
| Tømrer & Oppussing Walfred AS | Construction | 2025 |
| Tømrer Eirik Brødremoen AS | Construction | 2026 |
| Tømrermester Joakim Nilsen AS | Construction | 2021 |
| Tørres Holding AS | | 2020 |
| Union Eiendom AS | Real estate | 2023 |
| Unique Pyrotechnic AS | Arts & recreation | 2011 |
| Unni B Flønes Og Ivar M Sandem Ans | Agriculture & fishing | 1985 |
| Utemiljøgruppen AS | Administrative & support | 2012 |
| V M Deleservice AS | Wholesale & retail | 2008 |
| Vandugbakken Næringsbygg AS | Real estate | 2026 |
| Vandugveien 19 AS | Real estate | 2025 |
| Varde Utvikling AS | Real estate | 2026 |
| Vegard Støten Holding AS | Professional & scientific | 2013 |
| Veivalg Kompetanse AS | Education | 2020 |
| Vektergården I Mysen AS | Real estate | 2009 |
| Ventinspect AS | Construction | 2026 |
| Vestid AS | Wholesale & retail | 2023 |
| Vianka AS | Real estate | 2005 |
| Vidvinkel AS | Professional & scientific | 2015 |
| Virtue AS | Information & communication | 2021 |
| Wikholm Form AB | Wholesale & retail | 2009 |
| Winberg Produkter AS | | 2019 |
| Wiwi AS | Construction | 2018 |
| WP Skolen AS | Education | 2016 |
| Yaay AS | Other services | 2024 |
| Yl Holding AS | Other services | 2020 |
| Zawadi.No AS | Wholesale & retail | 2024 |
| Örtagården I Klevane Tone Brith Nevland | | 2002 |
| Øb Invest AS | | 2005 |
| Øko-Trykk.No AS | Manufacturing | 2014 |
| Ølkompaniet AS | Manufacturing | 2017 |
| Øph AS | | 2022 |
| Ørjeveien 124 AS | Real estate | 2005 |
| Øst & Vest Invest AS | | 2024 |
| Østfold Betongprodukter AS | Manufacturing | 1978 |
| Østre Invest AS | | 2022 |
| Østre Viken Transport AS | Transport & logistics | 2022 |