Taxpayer has refinanced several times since original purchase in 2000.  I have three closing statements (2009, 2010, and 2016).  Practically speaking, I know some of this is equity loan (versus acquisition), but since I do not have the 2000 closing statement nor do I know how much they used to make improvements to the home, what questions should I be asking the client and then how do I determine how much of the interest expense to exclude?  This seems to be extrememly complicated (and if we can't figure it out, how will the IRS be able to)?  I can see how to do this on new loans, but on ones that are old, I'm just not sure how to go about this.  Would be interested to know how others are handling this.