I don't think I have covered this before, but apologise if I have doubled up. In the situation of spouses banks will lend to both even though only one is on title. This includes both married and defacto spouses. I think all lenders allow this, but there may be a few exceptions. So where A owns the property and both A and B are on the loan who can claim the interest? Only A can as A is the owner of the property. Incidently this is generally not a good set up because 1. The non owner is exposed to the loan and is liable for the whole debt, and 2. The non owner has their serviceability significantly reduced because they will be liable for the whole debt and not have any of the rental income countered for serviceability. The only time this should be done is for serviceability reasons. Where the income of 1 is not enough both spouses can be used. Later perhaps the situation will change and the non owner spouse can come off the loan and then have their borrowing power increased.