I'd use 3/4" thickness, but ....
Depends on the size, but 1" thick material will way a ton if used in a large size chest.... 18 X 24 X 16 or so. Many new woodworkers use material that is too thick, because often that's all they can buy off the shelf. I use 5/16" and 3/8" thick thick material on smaller chests and keepsake boxes, and 1/4" thick on jewelry boxes.
It's a shame to plane down thicker material and waste 1/2 the thickness. If you can resaw it, you will save more material.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)