Use Year is the hardest concept to master! I found out at the very beginning of our ownership that I needed a spreadsheet, or else I was going to get very confused, even though all our points are at one resort and in one UY (we have 2 contracts, each 150 points).
The column headings are Date, Points Added, Points Used, Bank From, Bank to, Balance, and Notes. I have formulas built in so the spreadsheet does the arithmetic, which is why there's no column for borrowing, but you can do it manually of course.
The most important thing is that I input the dates our UY starts, so I can put any trip I'm planning into the correct UY, and that determines which points I can use (banked, current, borrowed).
And here are our first two years of use:
Date | EVENT (Can bank up to 100% by 4/30) | Points Added | Points Used | Bank From | Bank To | Balance | Notes |
11/26/97 | Purchase- Use Year Sept. 97 - Aug. 98 | 300 | | | | 300 | |
11/22-29/97 | Stay at Polynesian | | 94 | | | 206 | |
3/7-13/98 | Boardwalk | | 210 | | | -4 | |
9/1/98 | New Use Year | 300 | | | | 296 | |
11/20-23/98 | Cruise | | 412 | | | -116 | |
11/23-26/98 | Boardwalk | | 144 | | | -260 | |
2/3-4/99 | Boardwalk | | 22 | | | -282 | |
9/1/99 | New Use Year | 300 | | | | 18 | |
You might want to read this thread:
https://www.disboards.com/threads/understanding-use-year-updated-february-10-2021.1942668/