I have a client who purchased a home, second home for them, in 2016 for their son to live in, which he did.  The parents and the son are on the title and the mortgage.  The parents have taken the mortgage interest and property tax deduction each year.  They sold the home in 2019.  If the parents put the sale of the property on their tax return, they will incur capital gains tax, if the son puts the sale on his, he would qualify for the exclusion.  However, since the parents were the ones who took the deductions, would they be required to put the sale on their return?  Can you point me to any regulations about this type of scenario?

Thanks.