I assume by "partner" you are not legally married.
You can't deduct the property taxes. That's the simple answer, because property taxes can only be deducted by the person against whom the taxes are levied, and if you are not on the deed of the home, then the taxes are not levied against you.
Mortgage interest is a little more complicated. You are allowed to deduct mortgage interest that you pay, if you are a legal or beneficial owner of the property, even if you are on the deed or mortgage. "Beneficial owner" is a concept that you have a recognized right of ownership in the home even if you aren't on the deed. I remember two tax court cases about this. In one case, A bought a home for his brother B because B was a new immigrant with no credit history. B paid all the bills and was planning to take over the mortgage as soon as he could. The tax court ruled that B could deduct mortgage interest. In the other case, C moved in with his father D, who was elderly and somewhat infirm. C paid the bills, took care of maintenance and repairs, and expected to inherit the house when his father died. The tax court ruled that C could deduct the mortgage interest.
https://www.law.cornell.edu/cfr/text/26/1.163-1
So the real question is, under the laws and customs of your state, would you be considered to have a "beneficial" ownership interest in the home. (Maybe your state has a practice of awarding financial support similar to alimony when long time partners split. Or maybe there is some other reason that a court would recognize you had some rights in the property if there was a dispute of some kind.) Whether you qualify is something you will have to determine for yourself.
