Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
If you mean that the Zakah is put in a usury-taking bank and gets interest and you are asking about the lawfulness of using this interest in paying bills, the answer is as follows:
It is unlawful to put the money Zakah in a usury-taking bank unless there is no Islamic bank in the area, and there is a dire need to put this money in that bank for a short period before it is dispatched among its recipients (those who deserve it). If in that short period there is some interest on that money, then it should be spent in the interests of the Muslims in general. So, if these bills are for an institution that deals in gathering the Zakah and dispatching it, then it is lawful to pay them from this money, otherwise it is not.
Allah knows best.