You should enter the number that is on your copy of the 1099-R for the distribution. You will be asked follow up questions to determine whether it is a qualified rollover.
If your copy is blank in box 2a, leave it blank. If there is a number, enter the number.
If the amount went from a Traditional IRA to another Traditional IRA, or from a Roth to a Roth, the amount should not be taxable.
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