Reverse Unapplied Credit Memo in a Closed Period

1. On the Credit Memo page > Actions > GL Impact. 

Note the Accounts that will be used in the Reversal of Journal Entries.
2. Navigate to Transactions > Financial > Make Journal Entries.
3. List the Accounts (If it is debited in the Credit Memo, credit it in the Journal Entry).
4. Add the Name of the Customer in your Accounts Receivable type of Account
5. Navigate to Transactions > Customer > Accept Customer Payment.
6. Select the Customer and the correct A/R Account.
7.On the Apply tab> Locate and check the Journal Entry and the Credit Memo.
8. Unapplied Amount should be 0.
9. Click Save.

10.Verify this on Reports > Customer/Receivables > A/R Aging.

There is a pending Enhancement in creating a Debit Memo to Reverse Credit Memo - Enhancement 48386.