(IRS guidance on tax treatment of amounts homeowners pay to repair damage caused by corrosive drywall building materials (i.e., Chinese drywall); safe harbor provided allowing homeowners to treat some damage as casualty loss and method provided for determining amount of loss; applicable to amounts paid to repair damage to personal residence or household appliances as a result of the corrosive drywall; amounts within safe harbor can be treated as casualty loss in year of payment; amounts paid to restore residence to condition immediately before damage may qualify for casualty loss treatment; losses claimed for replacement of household appliances limited to lesser of current cost to replace or basis; guidance effective for all returns filed after Sept. 29, 2010).