Explanation to Section 271(1)(c) supports penalty where concealment is unproven, but references are restrained if not previously raised. The explanation to Section 271(1)(c) can support a penalty when concealment is not proven but assessed income exceeds returned income for returns filed after the relevant commencement date; where tribunals disallow such penalties the Board will file references to test the explanation, but will avoid or withdraw references in cases where the explanation was not raised before the Tribunal.