When closing on your mortgage, you will be asked to sign an IRS form called a 4506.
An IRS form 4506 requests a copy of one or more of your tax returns from the IRS. The lender may also want a form 4506-T signed, which requests a transcript of one or more of your tax returns.
Even on a stated income deal the lender can, and most likely will, require you to sign a 4506-T form so that they can verify your income at any time if they feel it is necessary. Even if it is after your loan has closed, the lender can still verify the income that you listed on your loan application. On a stated income deal you are not supposed to lie about your income. A stated income deal simply alleviates dealing with the income documentation requirements imposed by the lender for a slight increase to your interest rate. So therefore, keep this in mind if you are ever doing a stated income deal that you may be required to sign a form 4506T and the lender has the right and permission to verify the income you stated on your application is indeed the amount of income that you truly make.