A mortgage lender is asking for "self-prepared" verification for my taxes from the last 2 years. How do I find my "self-prepared" verification documentation in TurboTax?

Your Form 1040 will say "Self-Prepared" on it.   And you can give them the "electronic postmark" page that shows that the return was e-filed.  That can be printed out with the pdf pages of your return.   When you e-file, there is no physical signature on the tax return.  You "signed" it electronically by entering your AGI or PIN.   If they want a signature, take out a pen, sign it on page 2 next to the words "Sign here" and keep them happy.

The lender is asking for something that doesn't exist. There is no such thing as "self-prepared verification." Ask them to show you an example of what they are looking for. If they can actually produce an example, that will give you an idea of what you have to do.

If what xmasbaby0 suggested doesn't satisfy them, find another lender - someone who understands how tax returns are filed. Or you could try asking to talk to someone else who has more detailed knowledge of tax return filing.