We received an application for a pre-approval for a home purchase on 7/8/13. Address of property was on the application. We processed it and sent out early disclosures. Our bank does not have a pre-approval program.
Just received the PA yesterday. Do we use the applicatoin date of 9/17/13 going forward for HMDA reporting and disclosures??

What is a PA? Unless it's a valid changed circumstance, you shouldn't be doing more disclosures now.

From what you've said, you had the six items, including address, so it doesn't matter if you called it a pre-app or not. It was an application on 7/8/13 and you properly disclosed then.

Purchase agreement(PA). The purchase price decreased from the original amount we approved them for.

Receipt of a purchase agreement is not a valid changed circumstance so you can't redisclose based on anything in it.

Banks don't approve purchase prices. They approve loan amounts.
If the purchase price decreased, do the borrowers want to lower the loan amount? If not, then you could only redo the disclosure if they HAD to lower the loan amount for some reason.

But I wouldn't redisclose to lower the loan amount because it narrows my 10% margin. Our rule of thumb is that if we have a valid changed circumstance that allows it, we still only redisclose if we need to capture a fee or fee increase that was triggered by this changed circumstance.