-When you upgrade Chase pro-rates the refund of your existing card immediately. The new Ritz annual fee is charged in full and is not pro-rated. That happens roughly 3/4 months after you upgrade. It then reverts to the original annual fee date you had with the first card.
Thank you for the detailed explanation. If the upgrade is performed relatively close to the anniversary / original annual fee date, The $450 fee for the RC would then only cover a few months compared to a full year. I find this a bit surprising by Chase (as Amex actually pro-rates the upgraded card fee.). In this case wouldn't it be best to always upgrade just before or shortly after the original fee date ?