A client wants to use a prototype document to establish their 403(a) plan. Looking at the opinion letter it seems very specific that the document and opinion letter are specific to plans qualified under 401(a). Could a plan rely on the opinion letter if they are 403(a) instead of 401(a)? If not, can they use the prototype document and have it be considered an IDD?
Thanks for any help.

I can't imagine that any 401k prototype documents could properly accommodate a 403b plan. That is, I don't think you can properly document a 403b plan by adopting a 401k prototype.

What the client may have heard is that the IRS has promised that there will be 403b prototype program opened by the IRS sometime in 2009. In the meantime, it is important to operate the 403b plan "in accordance with a reasonable interpretation of § 403(b), taking into account the final regulations". IRS Notice 2009-3.

They are trying to set up a 403(a) plan, not a 403(b) plan. I think they are trying to get around fees for an IDD.

Also, I would not hold your breath waiting for the IRS 403(b) prototype program to open. It is unlikely that any IRS-approved prototype documents will exist before the end of this year (2009). The IRS spent two years reviewing the EGTRRA DC plans that were submitted before issuing final approvals. That's blazing speed on a geologic time scale.