Official Staff Interpretations to 12 CFR 1026.43(c)(4): 3. Tax-return transcript. Under § 1026.43(c)(4), a creditor may verify a consumer’s income using an Internal Revenue Service (IRS) tax-return transcript, which summarizes the information in a consumer’s filed tax return, another record that provides reasonably reliable evidence of the consumer’s income, or both. A creditor may obtain a copy of a tax-return transcript or a filed tax return directly from the consumer or from a service provider. A creditor need not obtain the copy directly from the IRS or other taxing authority. See comment 43(c)(3)-
IMO, in order for a tax return provided by the consumer to be deemed reasonably reliable you would need evidence that the tax return provided was filed.
