How do I invoke turbo tax to give me a credit for an IRA rollover?

Line 4a will show the full distribution amount and Line 4b will indicate only the taxable amount.   Enter your 1099-R and answer all of the follow up questions.   TurboTax will ask you what you did with the money and once you tell TurboTax that you rolled it over, the amount will move to 4b.     Where do I enter a 1099-R?

What did you roll it over to?  Another Traditional IRA or did you convert it to a ROTH IRA?  What code is in box 7?  

If it was within the 60 days, after you enter the 1099R it will ask what you did with it. Pick you moved the money to another account even if you put it back into the same account. Then that will expand and you pick I rolled over all this money. Then it will expand to enter how much you rolled over.

Did they take any withholding out of it? If they did you had to add it back in from your own money when you put it back or the withholding will become a distribution by itself.

If you are looking at a summary screen or review screen those show the full amount as income and lump a lot of stuff together. You need to check the actual 1040 form and make sure it's right. 1040 line 4a or 5a is just the gross amount.   Check lines 4b & 5b for any taxable amounts. For a rollover line b should be zero and the word Rollover by it.