What is the best way to deal with multiple credits we receive from partners. How can we reconcile them together and not one by one?

If you under delivered that month, and the campaign is still ongoing, you can adjust the future months to up the impressions. Systematically, there is a way to adjust future months in the delivery tab. It recalculates the impressions either as a bulk to the following up, or you can apply to the remaining months. This is also a good time to reach out to your supplier and ask why they under delivered and get a commitment from the supplier to deliver as ordered. If your campaign is set up in a way that you don't require approval for changes that does not affect overall budget, then you are good to go. It is always a good idea to spend all of the budget rather then getting credit. The backend finance does not like those type of credits and debits. If you need to apply the credit to other campaigns, it is best to wait until the campaign ends. The finance/accounting can be difficult if you are are constantly adjusting the total amount month per month per supplier. So, the goal is to spend as per budget and if you need to, apply under delivery to future months. Worse case scenario, you can update the total amount at the closing of the campaign. SO, SET YOUR CLIENT'S EXPECTATION. Once the budget is committed to a campaign, they will only be able to reallocate to a difference campaign after the campaign closes. Of course, there is always a way to take the monthly credits and apply to different campaigns, but this is NOT IDEAL. I hope this helps.