Uploading of customer master and opening balances are common during implementation process. But one thing currently lacking is to update the "Valid Collection letter code" and "Collection letter code". updating to these fields are very much required since in the legacy system Collection letter 1 or Collection letter 2 or Collection letter 3 or Collection letter 4 or Collection letter might have been generated for specific transactions, So it is obvious that in D365FO we need to update the "Collection letter code" and the next collection letter sequence to be generated from D365FO i.e. to the "Valid Collection letter code". Same concept goes at the Customer master as well, because D365FO has the parameter to generate the Collection letters based on Transaction specific or Customer specific.

Due to the above reason, In the Data management the respective data entities must include the "Valid Collection letter code" and "Collection letter code" fields and once opening balances are uploaded via General journal process and posted the values updated in the "Valid Collection letter code" and "Collection letter code" must update the same in the Customer open transaction and Customer transaction table for the respective transactions.

I assume at the customer master the "Valid Collection letter code" and "Collection letter code" displays the highest "Collection letter code" considering from the Customer open transaction and Customer transaction table. If not, then during the Customer master upload also "Valid Collection letter code" and "Collection letter code" fields to be added in the relevant data entity in the data management to update the right values.

With the above process change D365FO can handle the collection letter generation process rightfully in accordance with collection letter sequence configuration.