[quote} Auditor is threatening that audit will be closed unagreed if plan sponsor does not sign Form 56. Is this normal?
[/quote]
They need to get Form 56
http://www.irs.gov/pub/irs-pdf/f56.pdf signed so that they can issue summons for information from third parties. Here's a key quote from the IRS Manual:
"With the enactment of RRA 98, the notice procedures now apply to almost all third-party summonses. Therefore, the Service must accurately distinguish third-party summonses from those served on a taxpayer. In most situations, this distinction is obvious. However, it is less obvious in at least two circumstances: those involving married couples who file joint returns and those involving employees or corporate officers who are summoned in that capacity."
http://www.irs.gov/irm/part25/ch05s06.htmlIt does sound like you have a real audit under your hands.
George