Most IRS notices that afford procedural rights are required to be sent to a taxpayer’s last known address. The last known address is generally the address that appears on the taxpayer’s most recently filed and properly processed tax return, unless the IRS is given clear and concise notification of a different address. An inquiry into a taxpayer’s last known address is based on all of the relevant facts and circumstances. Generally the courts will examine what the IRS knew or should have known regarding a taxpayer’s last known address at the time the notice was issued.
Generally if is a notice is not sent to the last known address it is not valid, and the IRS may in some cases be prevented from collecting taxes which otherwise might be legally due.