I've had the Internet Help desk email these to me before. Call them and ask to be emailed a customer receipt. 800-327-7810 I assume they're still able to do it. Last time I got one was in January. You'll get a text only email that contains the fare construction. At the top of the itinerary there's also some mention of the E-TUV and its value. Here's an example of one that involved a $100 voucher:

/FC __SEP__WAS US BOS161.86GXRUNA2/TVD US WAS73.49UJRVNA4
/TVD LESS100.00USD135.35END ZPDCABOS XT6.80ZP5.00AYXF9.00
DCA4.5BOS4.5

You have to do the math in the fare construction in order to get to the pre-discount base fare, which in this case was $235.35 (and then add the taxes)