My father passed away in 2009, leaving funds in a checking account on which I am Joint Tenant. I paid all of my dad's medical bills and filed his final tax return for 2009. This week he (I) received a notice from the IRS saying he owes money from the 2007 tax year. My question is twofold--must we pay this bill from 2007, and how far into the future might I expect to receive a tax bill from the IRS for my dad's previous year's taxes? Thank you.