If the difference with the new tile is < or = 1/2", there are special wax rings specifically designed to compensate the gap…
If the difference is >1/2" there are closet flange kits available that fit into the existing flange. The fitted flange would be bolted around the perimiter of the existing flange for support.
I’ll see if I can locate an online source…
…anyway, just look at the depot for closet flange extensions or stackers.
Be sure to pick up longer bolts for the bowl!
Tim is right. they sell an extra thick wax ring for this application. but first make sure you scrape all the old wax off an check to make sure the flange ears aren’t cracked or broken off. the buildings i maintain are all from the 60’s and 70’s and i see busted flanges alot. but if it is busted, a “thread in” style p.v.c. flange replacement will fix both issues. hope that helps.