According to some Muftis only interest received from a government institution such as a post office may be used to pay taxes and fines, not bank inter

Answer

The claim that only interest received from a government institution may be used to pay taxes is baatil. There is no Shar'i basis for making this claim. The haraam oppressive tax may be paid with interest received from any other institution. There is no Shar'i basis for the averment that zulm taxes must be paid with only government money, i.e. only with the money of the zaalim or with one's own halaal money. If zulm tax can be paid with one's own halaal money, then to a greater degree will it be permissible to pay the haraam tax with haraam money such as bank interest.