| Slåtta Anlegg AS | Administrative & support | 2023 |
| Slåtta Holding AS | Real estate | 2021 |
| Smaken Av Lykke AS | Manufacturing | 2020 |
| Smedsrud Invest AS | | 2020 |
| Smil Estetika AS | Health & social care | 2017 |
| Snakkomåsy AS | Wholesale & retail | 2023 |
| Snikaparken Utbygging AS | Real estate | 2021 |
| Sol Og Eiendom AS | Other services | 2014 |
| Soloduo AS | Information & communication | 2018 |
| Solsikka Notodden AS | Wholesale & retail | 2003 |
| Solsta Live AS | Arts & recreation | 2018 |
| Spa Og Velvære AS | Other services | 2007 |
| Sperre & Eikeland AS | Real estate | 1986 |
| Sperre AS | Manufacturing | 1988 |
| Sperre Group AS | Real estate | 2007 |
| Spillorama Notodden AS | Arts & recreation | 2006 |
| Spinnvill Notodden AS | Arts & recreation | 2017 |
| Spire Merkevarestudio AS | Professional & scientific | 2025 |
| Spit Air AS | Administrative & support | 2000 |
| Sport 1 Tuven AS | Wholesale & retail | 2011 |
| Sports Partner AS | Real estate | 1991 |
| Spotlight Ans | | 1985 |
| ST Notodden AS | Wholesale & retail | 2023 |
| Stao No Pao AS | Administrative & support | 2014 |
| Star Bil Notodden AS | Wholesale & retail | 1993 |
| Stasjonsdrift Bvlarsen AS | Wholesale & retail | 2019 |
| Statsaut. Revisor Bjørn Enggrav AS | Professional & scientific | 1996 |
| Stein & Va Grossisten AS | Wholesale & retail | 2024 |
| Steinhaug & Kleven AS | Construction | 2006 |
| Stigo Holding AS | | 2024 |
| Stokker Invest AS | Other services | 2015 |
| Storeble Eiendom AS | Real estate | 1993 |
| Storeblevegen AS | Real estate | 1973 |
| Storgata 26 Notodden AS | Real estate | 2007 |
| Storgata 48 AS | Real estate | 2006 |
| Storgata Frisør AS | Other services | 2016 |
| STORGATA28 AS | Real estate | 2020 |
| Storgaten 60 AS | Real estate | 1995 |
| Storgt 62-64 AS | Real estate | 1999 |
| Strand-Lien AS | Real estate | 1970 |
| Strikkelåven AS | Wholesale & retail | 2022 |
| Studyflow AS | Information & communication | 2026 |
| Styling Hårsenter AS | Other services | 1995 |
| Stårheim Kraft AS | Energy | 2021 |
| Su-Hefre AS | | 2025 |
| Sukkervaregrossisten Ans | | 1989 |
| Sunbelt Holding AS | Wholesale & retail | 2021 |
| Sundstol Solutions AS | Construction | 2026 |
| Surtevju Drift AS | Wholesale & retail | 2006 |
| Svensdalen Eiendom AS | Real estate | 2023 |
| Svihus Vedlikehold Da | Construction | 2020 |
| Swampstamp AS | | 2021 |
| Sydfolier AS | Manufacturing | 2017 |
| Syftestad Gard AS | Hospitality | 2023 |
| Sør Arkitekter AS | Professional & scientific | 1986 |
| T.C.T Holding AS | | 2018 |
| T.Haugan Invest AS | Arts & recreation | 2012 |
| Ta Seksualiteten Din Tilbake Da | Education | 2024 |
| Tak & Håndverkstjenester AS | Construction | 2026 |
| Taklåsvegen SA | Real estate | 2025 |
| Takstmann Olav Øyen AS | Professional & scientific | 2021 |
| Tardigrada AS | Real estate | 2021 |
| Tbu Stillas AS | Construction | 2021 |
| Te Løkka Holding AS | Wholesale & retail | 2019 |
| TEGNESENTERET Sundseth og Løkja DA | Professional & scientific | 1990 |
| Teknisk Sprinkler AS | Construction | 2021 |
| Teknisk Va AS | Water & waste | 1984 |
| Tele Blikk AS | Construction | 2020 |
| Tele Eiendomsutvikling AS | Real estate | 2004 |
| Tele Feltutvikling AS | Real estate | 2015 |
| Tele Restaurantsenter Ans | Hospitality | 1989 |
| Telebygg AS | Real estate | 2013 |
| Telegata 4B AS | Real estate | 2008 |
| Telegata 7 AS | Real estate | 2022 |
| Telegata 8 AS | Real estate | 2022 |
| Telemark Bygg Utleie AS | Administrative & support | 2000 |
| Telemark Eco Technologies AS | Manufacturing | 2012 |
| Telemark Energy AS | | 2011 |
| Telemark Hotelldrift AS | Hospitality | 2023 |
| Telemark Internasjonale Parasenter AS | Arts & recreation | 2025 |
| Telemark Lagerpark AS | Real estate | 2021 |
| Telemark Lagerservice AS | Wholesale & retail | 2015 |
| Telemark Ring AS | Arts & recreation | 2021 |
| Telemark Ring Drift AS | Arts & recreation | 2025 |
| Telemark Sport AS | Wholesale & retail | 2009 |
| Telemark Technologies AS | Professional & scientific | 2012 |
| Telemark Technologies Holding AS | Professional & scientific | 2014 |
| Telemark Technologies Workshop AS | Real estate | 2018 |
| Telemark Teknologipark AS | Real estate | 2006 |
| Telemark Trafikktjenester AS | Transport & logistics | 2026 |
| Telemark Travel AS | Administrative & support | 2015 |
| Telemark Trykk AS | Manufacturing | 1991 |
| Telemark Utleie AS | Agriculture & fishing | 2016 |
| Telemark Vei- Og Trafikksikring AS | Administrative & support | 2017 |
| Telemarkens Bokhandel AS | Wholesale & retail | 2010 |
| Telemarksklinikken AS | Health & social care | 2024 |
| Telen AS | Information & communication | 1980 |
| Telerock AS | Hospitality | 2012 |
| Tem Service AS | Arts & recreation | 2025 |
| TEND4 AS | Wholesale & retail | 2025 |