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.
