If the copy is to show income for purposes of getting a loan, the bank needs to know that it is a copy of the return that was actually filed. If there is a receipt to show that it was electronically filed (and electronically signed) that may suffice. Otherwise, there is an IRS form that a partner can sign to allow the bank to get a transcript of the return from the IRS. You should talk to the bank about what will suffice.
I would advise using the filed return along with the e-file authorization which is form 8879. If it was a 1065 the form is the 8879-PE. That 8879 form should have a signature on it.
This is not legal advice nor intended to create an attorney-client relationship. The information provided here is informational in nature only. This attorney may not be licensed in the jurisdiction which you have a question about so the answer could be only general in nature. Visit Steve Zelinger's website: http://www.stevenzelinger.com/
To follow up on the other answers, I think it makes sense to find out from the bank what they will consider sufficient to show that the return was filed. I suspect a signed form 8879 shoud work. If you don't have what they need in your records, your tax preparer should have documentation showing proof of filing, and can provide that to you or directly to the lender.
My answer should be considered general in nature, not legal or tax advice, and not one that forms an attorney client relationship. I am licensed in Tennessee and Virginia.