If a tax return has been filed, and the calculation of the tax basis, etc. or tax amount, etc. stated in the tax return did not conform to the provisions of the national tax laws, or the tax basis, etc. or tax amount, etc. otherwise differs from what the district director of the tax office has found through their examination, the district director of the tax office reassesses the tax basis, etc. or tax amount, etc. pertaining to the return based on that examination.