ERR_CREDIT_MEMO on QuickBooks: Credit memo error. Root cause: Credit memo not properly linked to invoice, credit amount exceeds invoice total, or customer account does not have sufficient balance to apply credit. Step 1: Verify credit memo linked to correct invoice. Go to Customers > Credit Memos (or Invoices > Credit Memos). Find by customer or memo number. Open and check "Linked Invoice" or "Applied To" field. Should show invoice number memo is reducing. If no link, click field and select correct invoice from dropdown. Ensure invoice date and customer match memo. Step 2: Verify credit amount does not exceed invoice total. Check invoice amount and credit memo amount. Credit memo should not exceed invoice total. Example: if invoice $500 and memo $600, system rejects because cannot credit more than invoiced. If too high, edit memo and reduce to correct amount, or create separate memo for excess. Step 3: Check the customer account balance. Go to Customers > Customer List and select customer. View account balance or aging report. Check for open invoices or existing credits. If multiple invoices, may need specify which invoice credit applies to. Some systems allow credits to any open invoice; others require specific selection. Step 4: Ensure credit memo reason documented. Open credit memo and check "Reason" or "Description" field. Should clearly state why credit issued (e.g., "Return of defective goods", "Billing error", "Discount adjustment"). If blank, fill in. Important for audit and prevents disputes with customer. Step 5: Apply credit memo to invoice. If not automatically applied, manually apply. Go to invoice and look for "Apply Credit" or "Apply Memo" button. Select credit memo from list and confirm. Invoice balance should decrease by credit amount. If memo fully covers invoice, status should change to "Paid" or "Closed". Step 6: Send credit memo to customer for records. After successfully applied, generate PDF and send to customer. Include note explaining credit and how applied to account. If remaining balance after credit, include reminder of new amount due and new due date. Keep copy of memo and customer acknowledgment in records.