Interesting question @BatmanRay - I’ve never seen it done the same way in two different organizations. What kind of size or organization are you considering? Generally can be quite different between 10, 100, 10000 and so on.
This might sound curt, but literally have two (or more) separate conversations. If the calibration (i.e., merit pay bonus) conversation happens in December, make sure you have other conversations in October and January that are not tied to pay at all.