Any person, natural or juridical, including estates and trusts, liable to pay any internal revenue tax covering taxable year ending December 31, 2005 and fiscal year ending on any day not later than June 30, 2006 and all prior years, who due to inadvertence or otherwise erroneously paid his/its internal revenue tax liabilities or failed to file tax returns/pay taxes, may avail of the IVAP pursuant to RR 18-2006.