We co-own a home (50/50). I split the mortgage interest and insurance as TT asked for "your portion". Do I split the loan balance (original and end of year) too?

[jensmil]

We are on the same loan. TT doesn't specify for "your portion" on this page.

[Opus 17]

Who is "we" and is your mortgage balance more than $1million?

[jensmil]

Less than $1 million. My husband and my brother technically co-own the loan (both families file jointly with their spouses).

[Opus 17]

It doesn't matter how you answer as long as the balance is below $1m, it won't change the deduction.  Probably you want to use a value close to the true value for each person (similar to the starting value on the 1098) so the IRS doesn't think it's a funny looking amount.