Refunds on a credit card feed appear as adjustments to the credit card, but you can tie them to a specific vendor. That way both the credit card register and the vendor account are accurate.
We are moving to a credit card whose feed is unsupported. This functionality does not appear to exist. Either the vendor is correct and the credit card register is wrong or vice versa.
It seems that the functionality exists to attach a vendor to an "adjustment." We just need an interface that will do it. It would be very, very helpful.