Basically, the mortgage has nothing to do with the legal requirement to depreciate rental property. Even though you're not on the mortgage, you do have a vested interest in the property. Therefore you will claim mortgage interest and property taxes that *you* paid from the date of inheritance. Understand how this works for you so you don't get bit big time by the IRS years down the road here. I am assuming your mom passed in 2017.
Upon her passing the property should have been transferred to her estate. Then an estate return (IRS FORM 1041) would have been completed and included the rental property. All prior depreciation taken on the property would have been recaptured and taxed to the estate. Then estate, and NOT YOU would have paid any and all taxes due on the property, up to the date it was formally, officially and legally transferred to you in your name.
Your acquisition date of the property would be the date your name was put on the deed. If there was already a renter in the property at the time, then the in service date would be the same.
For the purposes of depreciation, your cost basis would be the FMV of the property on the date of your mom's passing, and NOT the date you inherited it.
Below in the answer box is more information that you will find informative, educational and helpful. If you have any questions or need further clarification on this rental stuff, please ask. I've been a landlord for 25 years and while I do learn something new every day, I do have lots of experience with rentals and am more than willing to share my knowledge.
