Amtrak Guest Rewards - Adding AGR after booking ticket?

Is it possible to add the AGR number to a reservation after booking? I am travelling tomorrow so rebooking would be a $50 hit.

Is it possible to add the AGR number to a reservation after booking? I am travelling tomorrow so rebooking would be a $50 hit.
Yes, but AFAIK, you'll need to call Amtrak (1-800-USA-RAIL) to do so. I don't think you can do it online.

If you can't find time to call, you can always mail or fax (or possibly with AGR even email) copies of your ticket stubs in for credit after the fact.

I've done it in person at the station, too, if you don't have time to call in advance. (Obviously, this only works if the station is staffed.)

You can also apply for retroactive credit on the AGR website:

https://www.amtrakguestrewards.com/index.cfm?category=RetroCredit&loc=frmRetroCredit.cfm

The last time I used it, the points posted within 2 days.

I called and added the number. The entire call, including Julie, took 80 seconds. ^

If you get the ticket from a QuikTrak machine, you can also enter the AGR number at that time.