66. Amendments to return.—

The Commissioner may, on an application made by a taxpayer within such time, on such terms and in such manner as may be prescribed, grant such taxpayer a permission to file an amended  return  after removing the clerical mistakes and omissions from such return; but the Board may determine the surrounding circumstances on the basis of which a decreasing adjustment may arise as a result of any amendment made under this section and returns may be filed without paying monetary penalty.