I have 0 points in my September 2018 UY. I have all my points in my September 2019 UY. I want to book a room in July 2019 .... can I borrow from my 2019 points? Thanks for helping me with this.
Yes, you can. If, however, you banked points from September 2018, those points can not be un-banked. Banking and borrowing are final transactions. The only points you can borrow are the September 2019 points.
When you go to make the reservation on line, it will tell you that you have no current points to make the reservation and will ask if you want to borrow points. Remember that borrowing is a final transaction and if you need to cancel that trip in July for a later time, those points will expire on Aug 31, 2019.