No.
"If you see a 0 (zero) in Box 2a of your 1099-R paper form, the entire distribution amount in Box 1 is nontaxable.
However, if Box 2a is blank (empty) on your 1099-R form, the taxable portion of your distribution needs to be calculated:
- If the distribution is from a Traditional IRA, we'll ask you some questions regarding your non-deductible contributions and then calculate the taxable amount based on your information.
- If the distribution is from a pension, we’ll consider the entire distribution taxable unless you can calculate the taxable amount and enter it in Box 2a. Don't enter an amount unless you know the taxable portion of your distribution."
TurboTax FAQ: Is my distribution [1099-R] nonntaxable if Box 2a n my 1099-R is zero or blank?