If an NCO gets a letter of reprimand, that's filed locally, does it have to reflect on his NCOER?

A locally filed reprimand usually results from a violation that was not sooo egregious. The eater and senior rate in this case have more options. If they choose not to annotate the issue in the rating and the NCO later fails in the same it other areas, it can be posted in the OMPF. So the lesson is not whether the issue can be posted in the rating, it is get your stuff together and fly right. Your leadership has given you an opportunity to keep your career on track. Thank you for your service.

It doesn’t have to in a regulatory sense, though usually it represents a significant enough event or shortcoming that an unbiased evaluation of the rating period would make note of it.
Any time I was hesitant to talk about something on an NCOER, I kept in mind it was an honest and unbiased document representing the truth. It was what it was, if something good, bad, or ugly was important or representative during that rating period, consequences of the document were also honest and unbiased.

The reprimand itself doesn't have to be referenced. Like a 1059 it's located in your file. However, the issue it references should be addressed. For instance, if it was a DUI or gross negligence that led to the reprimand, the rater would be remiss not to address it in the Soldier's evaluation.
If the reprimand were appealed and removed at a later date, the soldier would be eligible to contest the NCOER and have it removed.