How does NonRated time work? Can I request it? Is it a detriment to future promotions?

Ensure that when they do finally do your NCOER, that they include the proper codes for your non-rated time. 1SG (Join to see) already hit the nail on the head with the regs. Examples of non-rated codes include transition, schooling, etc.

CSM (Join to see) your reference is DA PAM 623-3, Table 3-7. Most likely you had a deployment like most of us and it was a year, rating a period of 30 days of leave (Code E). Since you are mobilizing, you change of duty status forces a change of rater report unless rater qualification (90 days) is not met. So the question is, did they assign you to a rater, and was he/she in position for 90 days? If so, you should receive a report encompassing the entire period from your last report until your mobilization date. If not, you would receive an extended annual report with Codes E and Q accounting for the period you were assigned-not joined. As to what is most beneficial, a report with most likely nothing substantive or a non-rated period, that is a judgment call. Generally, I prefer to account for the time as a rated period, with a Letter of Input from whomever was in charge of you while you RST'd or whatever in the interim.

Thanks for all the feedback here. I have since become a guru on the subject. If anyone else finds themselves in the same position. Feel free to let me know.