After his Abitur, Kimmich became an apprentice at a private bank in Ulm before studying political economics, in which he promoted in 1906.
This lasted until 1915, when he went to the Cologne head office of this bank where he became over the years one of the best adepts of the Rhine-Ruhr area.
During the Nazi era, Karl Kimmich was heavily involved in the "Aryanization" of Jewish firms carried out by Deutsche Bank.
On July 25, 1938, he mentioned in a file note that 260 out of 700 Jewish firms listed by the bank's headquarters had been Arianized.
By November 1938, shortly before Kristallnacht, he could report to official ranks that his company had arranged so far 330 "arianisations" that were mostly concluded.