Dues are based on calendar year, not UY. It doesn’t matter when your UY is.
There’s been a lot of discussion about paying current dues. My philosophy is, if you have 2019 points (either current or banked), it is reasonable to pay the 2020 dues. If you only have 2020 points, it’s also reasonable to split the dues with the seller. With an Oct UY, I might request they pay 9 months of dues and I pay 3 months.
That said, my experience has often been in buying 6 contracts that sellers seem less willing to negotiate around dues than they are price per point. (Go figure; they’ve already paid their 2020 dues; I would’ve thought this would be the easiest to negotiate!) so I actually tend to factor in the dues to reduce the price per point I offer and pay the dues.