The Internal Revenue Service will allow taxpayers to write off repairs to damage caused by problematic drywall installed in homes between 2001 and 2008. Homeowners have reported certain drywall imported from countries, primarily China, to cause blackening or corrosion of copper electrical wiring in appliances. In November 2009, the Consumer Product Safety Commission sampled the air quality of 51 homes and found a link between the drywall and levels of hydrogen sulfide and metal corrosion in those homes. In June, the government-sponsored enterprises announced they would keep homes with the problematic drywall out of the foreclosure process. Under the IRS guidance issued Thursday, taxpayers who have already filed their income tax return for the year they paid for repairs have three years to file an amended return and claim the reduction. The loss that may be claimed depends on whether or not the taxpayer has a pending claim for property insurance loss or loss mitigation reimbursements. If there is no pending claim, the taxpayer can claim all the repair losses. If there is one, the taxpayer can claim up to 75% of the repairs. If the taxpayer has already been reimbursed for the insurance or loss mitigation loss, he or she cannot write off the repairs. Write to Jon Prior.