When you receive a Change of Rater NCOER, does that change your through date?

Ar 623-3 para 3-40 and 3-41 provide the answer
simply put, the through date is what it is on what ever report is being submitted, Annual, Change of rater, complete the record.
The next report period starts one calendar day following the last report through date.

Sure does, funny but my annual is due 10 July, but my rater will change out on 7 July, so in lieu of a annual it will be a COR, so yes, it changes the thru date, even if 3 days to the left!

Your 'thru' date is established by whatever event is causing an evaluation to become due. Your date of rank as an NCO or date of accession as an officer establish the start point for any evaluation but you are not tied to that date forever. The key date is actually the day you fall under your rater. 365 days after you start with your rater, an annual is due. If something causes you to change your rater prior to that date, then an evaluation will come due i.e. Rater changes, you change duty positions, you go on TDY for more than 90 days, you get relieved...