Where any assessment to tax, or any duplicate of assessment to tax, or any return or other document relating to tax, has been lost or destroyed, or been so defaced or damaged as to be illegible or otherwise useless, HMRC may, notwithstanding anything in any enactment to the contrary, do all such acts and things as they might have done, and all acts and things done under or in pursuance of this section shall be as valid and effectual for all purposes as they would have been, if the assessment or duplicate of assessment had not been made, or the return or other document had not been made or furnished or required to be made or furnished :
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The references in subsection (1) above to assessments to tax include references to determinations of penalties; and in its application to such determinations the proviso to that subsection shall have effect with the appropriate modifications.