Wiki Obligation is not contracted with secondary payer

[AlaskanCoder]

We frequently run into the scenario where we may be contracted with a primary payer who indicates a contractual adjustment on the primary EOB which the secondary payer does not utilize in processing their payment. Some individuals in the office believe that, because we have contracted with the primary to accept their allowed amount as payment in full, we are obligated to refund the secondary payer for the amount of the adjustment. For instance, we submit a claim for $140 to PPO payer #1 who allows $120 and pays 80% or $96.00. We submit the secondary claim to the non-PPO payer who allows $140 and subtracts the primary payment and pays $44. Because we have already taken the $20 contractual adjustment for the PPO payer, we show a credit of $20 on this claim. Are we obligated to send a refund to the secondary payer? Also, does anyone have any credible citations for either response?
Thank you for your help,
Karen Hill, CPMA, CPC
DHCM
Anchorage, AK