Today, Treasury and the IRS issued proposed regulations (REG-134219-08) relating to relief from joint and several liability under section 6015 and relief from the operation of state community property law under section 66.  The proposed regulations make a number of significant changes to the existing regulations, including providing additional guidance on the judicial doctrine of res judicata and the section 6015(g)(2) exception to res judicata when a requesting spouse did not meaningfully participate in a prior court proceeding, and adding a list of acts to be considered in making the determination as to whether the requesting spouse meaningfully participated in a prior proceeding.  In addition, the regulations propose a definition of underpayment or unpaid tax for purposes of section 6015(f); provide detailed rules regarding credits and refunds in innocent spouse cases; expand the rule that penalties and interest are not separate items from which relief can be obtained to cases involving underpayments; incorporate an administratively developed rule that attribution of an erroneous item follows the attribution of the underlying item that caused the increase to adjusted gross income; update the discussion of the allocation rules under section 6015(c) and (d); and revise the rules regarding prohibition on collection and suspension of the collection statute.  Comments are due by February 18, 2016.