Resolution: 

Two Options for reports to show Credit Memos and Write Offs:  

Option #1: 

1. Run the Invoice Register report under My Stuff > Reporting > Report type Accounts Receivable.
2. In the report Options > Options tab, check the box for Only Include Credit Memo Details.
3. The report will only display the Credit Memos created in Interactive Billing.  

Option #2: 

1. Run the AR Ledger report under My Stuff > Reporting > Report type Accounts Receivable.
2. In the report Options > Options tab, check the box for Include Modification Detail.
3. This will list all posted invoices and any modifications on the invoice through the transaction center including cash receipts, and credit memos.