As of tax year 2018, the PMI deduction is currently unavailable. As of now, it is uncertain when, or if, Congress will approve this deduction for tax year 2018, 2019 and beyond. At this time, there is no estimate of when a final decision will be made.
If the deduction is approved after your file your 2018 Tax Return, you can file an Amendment to claim the deduction. Here are the instructions to do so: How to Change a Tax Return You Already Filed.
Alternatively, you can wait to file your Tax Return until Congress definitively approves or denies the deduction.
