Please ask your administration to 7.6.6 Set up Flexible Payment Plans (FPP) before this feature is working for you (Version 2.81 and up). Currently ADvendio supports the following two use cases. If theoretically both cases could apply the selected publication date (case 1) will will over the second case. 

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1. Create your media campaign and
2. add the campaign line items you like to sell and set the checkbox: "Invoice at the end of runtime".
   
3. Save your campaign items.
4. You will find the newly created flexible payment plan record in the related list of each campaign item.

3. Advance or Prepayment

Version 2.99 and up prevents automatic creation of FFP in case of PrePayment. Technically you will have to have the following setting:

1. Create FlexiblePaymentPlan Automatically checked in the AdminSettings AND
2. Media Campaign with the following Payment Settings:
   • Payment Due Date = "due at beginning of interval"
   • Payment Interval = "total account (one Invoice)"
   • Payment Start = "before / during Billingperiod"

Then the system will automatically skip the FPP creation for all Campaign Items of the MediaCampaign (even if CI checkbox "Invoice at end of runtime" is checked)