We're doing a 90day review for a SAR filing and will re-file. Since the last re-file we've had to several amendments (identification info for the business was not completed on any of their 3 filings so we had to amend all three SARs over the last month). When referencing in the narrative the DCNs for those previous filings, do we mention the old DCNs, the fact that we amended, and then list the new DCNs? Or do we just list the new DCNs and omit any mention of the amendments?

If it was me, I would list the amended DCNs only. No need to further confuse potential law enforcement reading the narrative. Give them the DCN for the previous SAR you want them to read (that is complete and accurate).

Actually my coworker called FinCEN, not knowing I was posting here, and they said to like the old DCN, the fact that it was amended, and then the new DCN number.

Probably not a great idea to question the response of people who should really know the answer, but that makes absolutely no sense at all. An amended SAR is the complete document. There is no need to reference the original or any intervening amendments. I'm pretty sure whoever you spoke with just made that up.