Diagnosis
In the down payment chain contract data you have selected a balancesheet account under the account assignment data.

System Response
In Customizing the system check whether account assignment to balancesheet accounts is allowed and correspondingly displays an information,warning or error message.
By default account assignment to balance sheet accounts is not allowed.

Procedure for System Administration
This message is controllable in Customizing for Debit-Side andCredit-Side Down Payment Chains.