For 2008 and earlier plan years, is there any place on the 5500 or any Schedule where the EIN of a mutual fund held as a plan asset might have to be identified? (No response relating to Schedule C reporting for 2009 and later is necessary, thank you.)

I can't think of a situation where a mutual fund (registered investment company) held as a plan asset would need to have an EIN reported.

Now if your 'mutual fund' is really a common/collective trust, then the answer is 'yes' on the Schedule D.

TPAMan: Good point. I meant a 40 Act registered fund.