I have 2 mortgage interest forms 1098. One has a refund of overpaid interest in box 4. How do I enter this and where?

I believe you are asking what to do with this amount as there is no box for its entry in the program. 

You can handle that in 1 of 2 ways depending on what year the interest was overpaid for.

1) A refund of interest paid this year would have to reduce this year's interest deduction.  You can accomplish this in TurboTax by entering a negative amount in Box 1 on the Form 1098 entry.   (this is probably not the case as you mortgage company would likely have reported this separately)

2) A refund of interest paid in a previous year would need to be reported as Other Income on line 21 of your Form 1040. You can enter that other income by following the directions below:

• Click on Federal Taxes
• Select Wages and Income
• Scroll down until you find the line Other Miscellaneous.
  
• Enter the amount from Box 4 and answer the remaining questions to be sure it is categorized correctly.

You can find more information on this topic in IRS Publication 936 at:   www.irs.gov/pub/irs-pdf/p936.pdf