You shouldn't have to check Box 7 in order to get Turbo Tax to apply a deduction. Turbo Tax just needs to know if the 1098 mortgage interest data applies to your main or second home and it will ask you about that after entering the 1098 data. I don't know why Turbo Tax includes Box 7 on the 1098 entry page. A check in Box 7 only indicates your mailing address on the form 1098 is the address of the property securing the mortgage. If this is your home and box 7 is not checked, the address in Box 8 may be a more legal description.
The 1098 form data you are entering doesn't get sent to the IRS with your return. The IRS gets a copy of your 1098 from the lender. If you have to check Box 7 in order to get the deduction, I wouldn't worry about it but go back and make sure all of entries are correct for the questions that come after entering the 1098.
