Core transistors typically have a maximum voltage rating between any of the 4 nodes (GDSB). If you exceed this voltage you can have reliability issues. Small overdrives can be tolerated with reliability reduction, Higher voltages cause gate oxide breakdown and finish your transistor directly. Normally you do not want to go above the core voltage.

In some analog circuits and if your CMOS process supports it, you can use deep-nwells to stack transistors and get higher volgages like PA's, otherwise you can use IO transistors that typically support higher volgages (2.5,3.3,5V) but can be slower.