By forms do you mean templates? By “Separate” do you mean different ssrs design that is printed for Credit note?
Also can you enable Discover report technical name in User options > Account > Docentric settings and print the report to see which report is executed.
As there is no separate SSRS report for credit note, one approach that you could pursue is to create a separate template for credit note and then create Conditional print management setting that prints the new credit note template. Condition that you could use would be for example if Invoice amount < 0:
as I have mentioned previously there is no separate standard SSRS report for Credit note in D365FO therefore it won’t be printed that way. You can distinguish between them by looking at the Document title on the printed SalesInvoice.Report or PurchPurchaseOrder.Report.
You can create completely new template for the scenarios when Credit note is printed and assign it to the Conditional print management setting as described in my previous reply. This way when Invoice amount is less than 0, your custom template for Credit note scenarios will be used.
The conditional Print management settings looks correct and to have your new template printed when that conditional setting is triggered, you need to specify your new “Credit note” Template within the Print destination settings: