I am sorry if this has already been posted, but I was unable to find any mention of this.
Currently when you buy land a handy box comes up and included in that box is information about your current land use tier and what your tier will be after you buy the land. Can something like this be added to the Group Information window, under the tab Land & L$, where you can add Your contribution: X sq. meters (Y max). If you owned a larger amount of land in a prior billing cycle, your value for Y will be the max of that tier. As a result there is no warning before entering the next tier in this instance.
I will use what happened to me as an example to what I am talking about. Last billing cycle I had enough land so that I was in the $75 a month (16,384 m2) land tier. I sold that land and this cycle I decided that I would only enter the $25 a month (4,096 m2) land tier. During this cycle some people moved to the land adjacent to my own and I decided that I would let them use some of my land. They are a military group so there is frequently prim spam on the land so I decided that I needed to have their leader clean it up as I cannot be online all the time to take care of it. I proceeded to create a group to aid in this. Keep in mind that I am currently at 4,608 m2 (4,096 + 512 I get with the premium membership) which is the limit of the $25 a month fee. I contributed 2,048 of land to the group, then I took the 2,048 of land they are using and deeded it to the group. Unknown to me was that in doing so, the system saw that as having a total of 6,656 m2 of land (4,608 that I own + 2,048 that was my contribution), even though all I actually owned was 4,608 m2.
I know that my example might be hard to understand, but what I am basically asking for is a tier change notification similar to the buy land window when contributing land to a group.