| Stena Line Norge AS | Transport & logistics | 1964 |
| Stenseth Grimsrud Arkitekter AS | Professional & scientific | 1983 |
| Stensrød Holding AS | Real estate | 2012 |
| Stis Invest AS | | 2022 |
| Sto-Nor Holding AS | Manufacturing | 2005 |
| Stor Med Stil AS | Wholesale & retail | 1999 |
| Stora Lee Hytter AS | Real estate | 2006 |
| Stordalsveien 541 AS | Real estate | 2020 |
| Storgata 1 Halden AS | Real estate | 1976 |
| Storgata 22 Halden AS | Real estate | 2021 |
| Storgata 27 Sarpsborg AS | Real estate | 2025 |
| Storgata 5 Halden AS | Real estate | 2013 |
| Storgata 7 Halden AS | Real estate | 2004 |
| Storgata Eiendom Halden AS | Real estate | 2013 |
| Storgaten 12 Halden AS | Real estate | 2015 |
| Storkleva Holding AS | Professional & scientific | 2019 |
| Stormkast Utvikling AS | Professional & scientific | 2018 |
| Strak Forvaltning AS | Real estate | 2013 |
| Strand & Grønnern Ans | Real estate | 2002 |
| Strand Larsen Holding AS | | 2025 |
| Strandbergs Stanseknivfabrikk A/S | Manufacturing | 1970 |
| Strikkeholdeplassen AS | Wholesale & retail | 2014 |
| Studio Sans AS | Wholesale & retail | 2021 |
| Stærk AS | Wholesale & retail | 2008 |
| Stærkere AS | Real estate | 2021 |
| Sund Leadership AS | Professional & scientific | 2021 |
| Superdry Norway AS | Wholesale & retail | 2008 |
| Superiore Capital AS | | 2019 |
| Sushi & Wok AS | Hospitality | 2016 |
| Svalbard Kjernekraft AS | Professional & scientific | 2025 |
| Svalsgård Ans | Agriculture & fishing | 2020 |
| Svarthamar AS | | 2021 |
| SVB Invest AS | Financial services | 2005 |
| Svenco AS | Information & communication | 2024 |
| Svendsby Bygg AS | Construction | 2016 |
| Svendsby Og Sønner AS | Transport & logistics | 2000 |
| Svenskegata 8 AS | Real estate | 2023 |
| Sverre Caspersen AS | Construction | 2000 |
| Sverre Caspersen Holding AS | Construction | 2005 |
| Svinesund Næring AS | Real estate | 2014 |
| Svinesundparken 7 AS | Real estate | 2021 |
| Svinesundparken Apotek AS | Wholesale & retail | 2015 |
| Svinesundplatået 1 AS | Real estate | 2020 |
| Svinesundplatået 2 AS | Real estate | 2026 |
| Svinesundplatået 3 AS | Real estate | 2026 |
| Svinesundplatået 4 AS | | 2026 |
| Svinesundplatået 5 AS | | 2026 |
| Svinesundplatået 6 AS | | 2026 |
| Svinesundsveien 319 AS | Real estate | 1963 |
| Svinesundsveien 329 AS | Real estate | 2026 |
| Svinesundveien 330 AS | Real estate | 1983 |
| Svinesundveien 334 AS | Real estate | 2010 |
| Svinesundveien 334 B AS | Real estate | 2019 |
| Svinesundveien Holding AS | Real estate | 2012 |
| Svingen 11 AS | Real estate | 2018 |
| SW19 Holding AS | Professional & scientific | 2012 |
| Swe-Nor Mekaniske | Wholesale & retail | 1997 |
| Sweetmood AS | Wholesale & retail | 2021 |
| Sydsiden Holding AS | | 2025 |
| Sydsiden Legesenter AS | Health & social care | 2015 |
| Sydsiden Tannhelsesenter AS | Health & social care | 2026 |
| Sydvang Holding AS | | 2019 |
| Synvi AS | Information & communication | 2026 |
| Systemfag Norge AS | Education | 2017 |
| Sötten Atten Da | | 2026 |
| Sølvgata Legesenter AS | Health & social care | 2025 |
| Sørhalden Fysioterapi AS | Health & social care | 2015 |
| Sørli Industri Og Lager AS | Real estate | 1969 |
| Sørli Renhold AS | Administrative & support | 1970 |
| Sørlie Verktøyindustri AS | Manufacturing | 1997 |
| Sørliveien 118 AS | Transport & logistics | 2012 |
| Sørstrøm Holding AS | | 2021 |
| T & P Eiendom AS | Real estate | 2013 |
| T G Consulting AS | Professional & scientific | 2011 |
| T-Bjerkeli Holding AS | Wholesale & retail | 1997 |
| T.L. Invest AS | | 2005 |
| T.O Holding AS | Real estate | 2021 |
| T.S-Holding AS | | 2023 |
| Taekwondo Halden Da | Arts & recreation | 2006 |
| Takst-Huset Øst AS | Professional & scientific | 2024 |
| Takstfag AS | Professional & scientific | 2014 |
| Takstmann Karsten E. Strand AS | Real estate | 2012 |
| Tamari Holding AS | Real estate | 2020 |
| Tannlege Anders Skaare AS | Health & social care | 2018 |
| Tannlege Ida Christine Buer AS | Health & social care | 2018 |
| Tannlege Jol Anders Mjølnerød AS | Health & social care | 2024 |
| Tannlegene Berg AS | Health & social care | 1998 |
| Tannlegene I Niels Ankersgate 5 Da | Health & social care | 2004 |
| Tannlegene Mork-Knutsen AS | Health & social care | 1994 |
| Tannlegene Tafjord AS | Health & social care | 2014 |
| Taube I Vika Da | Arts & recreation | 2011 |
| Tauro Invest AS | Wholesale & retail | 2005 |
| TB Printsolutions AS | Professional & scientific | 2016 |
| TDM 2 AS | Real estate | 2022 |
| TDM AS | Administrative & support | 2018 |
| Team Eiendom AS | Wholesale & retail | 2001 |
| Team Eiendom Violgt 3B AS | Wholesale & retail | 2012 |
| Team Elektro Halden AS | Construction | 2004 |
| Teatergata AS | Real estate | 2025 |
| Tectis AS | Wholesale & retail | 1988 |