We are the plan sponsor of a prototype document, used by many employers. The plan assets are held in accounts with us. So technically, we could be the custodian as in having custody of?

The schedule P requires the signature of a fiduciary (or custodian). I think, with respect to the schedule P, custodian means custodian of an ERISA 403(B), not a 401(a) plan. This means that for a 401(a) plan, we must not sign as fiduciary, the trustee or other fiduciary as designated by the plan, should sign as fiduciary. Am I Right?

The only time that I've seen the Schedule P have any significance is an IRS audit -- where the party signing the Schedule P was the one who had to sign the extensions of the statutes of limitations (in order to give the employer additional time to negotiate with the IRS).

Therefore, its probably best to have the Schedule P completed by the fiduciaries who would have the most "relevance" in that process.

I think nobody can tell if you are right or not based on the facts presented. Whether you are a custodian or not depends on the agreement you have with the plan/trust. There is nothing that I am aware of that limits the definition of custodian to 403(B) arrangements. That doesn't mean that it doesn't exist, just that I haven't seen it. I have seen financial institutions sign as custodians without being trustees of 401(a) plans.

Thanks
Mike Preston, the schedule P instructions state ( under who may file)... trustee of trust...401(a) an custodian or custodial account as described in Code section 401(f).

401(f) suggests a 403(B)(7) , in my opinion