Now taxes are in control of the dukes, bankers should be able to distribute these taxes according to the biggest contributors(not only in gold but also in food to the automatic food distribution system).
For example duchy A has all regions under the bankers distribution system and the city pays about 35% taxes and duchy B sells it's food for high prices out side the distribution system and pays no taxes, in this case tax should be distributed amongst all nobles in duchy A, not in duchy B.