Corrective Amendment after Plan submitted for Favorable Determination Letter

A plan was submitted for a favorable determination letter and the IRS found a problem with the date a participation agreement was signed.  We amended to change the company name and EIN and the date signed conflicts with the prior agreement.  Can a plan be retroactively amended to correct this type of error once the plan has been submitted?

I would ask the reviewer for their input. I've found them to be pretty lenient on minor issues like this when they are the only thing standing in the way of closing out a favorable DL. Even if it can't "officially" be amended retroactively, we typically have no problem amending during the DL process to accommodate their requests.

EBECatty makes a great comment as to asking the reviewer for their input. 

Is this an adoption agreement?  If so,  my understanding is a change in the company name/EIN is a front page swap change that does not require an amendment.  As an aside, ensure this change is indicated on the Form 5500 in year stating the company/EIN change or you will have other issues down the road.  

Obviously, it's really bad (I won't get into the details) to backdate documents. So you want to make it clear to the reviewer that nothing like that was attempted. I'm not clear on your facts, but if that is a potential inference, you want to proceed REALLY carefully, and legal counsel may be advisable.