Provisional for Doubtful debts

Hi,

My client, doesn't want to remove doubtful debts from the customer aging report, so @ end of each year they post the total amount as doubtful debts without specifying any customer details. The breakup of the amount(individual customer-wise) would be maintained by them outside SAP.

How to post into Doubtful debts account? where to credit & debit?

Thanks in advance!