The broker would code the distribution as "early distribution, no known exception." Turbotax will ask if any exceptions apply, and you be able to enter the amount of your prior contributions and any other prior withdrawals. If your contributions are larger than your withdrawals, the withdrawal will not be taxed. You don't attach any documents or proof to your tax return. Your signature of your tax return is your self-certification that your figures are true and accurate. If the IRS decides to audit you (less than 1% are audited), then it is up to you to show by records and other information that your figures are accurate.
