The department may collect any tax:
In any such case in a proceeding for the collection of such taxes, the person against whom they were assessed shall not be permitted to set up any ground of defense that might have been determined by the department, the Board of Finance and Revenue or the courts: Provided, That the defense of failure of the department to mail notice of assessment or reassessment to the taxpayer and the defense of payment of assessment or reassessment may be raised in proceedings for collection by a motion to stay the proceedings.
72 P.S. § 7241