As per this Bug: https://msdyneng.visualstudio.com/FinOps/_workitems/edit/656342

The Collection letter and the Interest note get created for a customer account 'Table' even if the Collection letter sequence and Interest code field is left blank for the Customer Posting Profile. This is when the Customer 'Group' setup exists for the same customer account with the Collection letter sequence and Interest code filled.

As per this document: https://docs.microsoft.com/en-us/dynamics365/finance/accounts-receivable/customer-posting-profiles#creating-a-posting-profile

The system Selects the identifier of the collection letter sequence to use for customers to whom the posting profile is assigned. This means that the selections are set up for the entire posting profile. If it doesn't find the collection letter sequence and the Interest code in the Table, then it will look to the Group or All settings. Hence, ‘Table’ is first as per the Search Priority but the system is selecting the setup specified for the customer account from the ‘Group’ since the setup was blank for ‘Table’.

Workaround: The posting profile does not work as some other areas with Table, Group, All. In standard F&O the way to get this to work is to add each customer at the 'Table' level and leave the collection letter sequence and Interest code blank. These customers that are set up at the 'Table' level can NOT be assigned to any of the 'Groups' that are in the same Posting profile. If they are assigned to any of the groups then the 'Group' settings will apply and create the collection letter and Interest note based on the 'Group'.

Expected result: As soon as the customer account is matching with the 'Table' setup, the system should apply rules set up there and not look for the setup at the next level, which is 'Group'.