Apply a Credit Memo on the Credit Transaction

1. Go to Transactions > Customers > Issue Credit Memos > List (Administrator).
   
2. Click Edit next to the memo you want to apply.
   
3. On the Items subtab, check the Auto Apply box next to the Unapplied field if you want NetSuite to apply the credit amount to the oldest invoices or cash sales due.
   
4. Click the Apply subtab to apply the credit toward a specific invoice or cash sale.
   
5. Check the Apply box next to the invoices or cash sales you want the credit applied to.If you use the Multiple Currencies feature, only invoices or cash sales in the currency of the memo are shown on the Apply subtab.
   
6. Click Save.

Now, when you include the credited invoice or cash sale on a customer payment, the balance due reflects the credit amount.

You can also apply credit memos when you enter a customer payment.

When you enter a customer payment, you can also apply open credit memos for that customer. This is useful when a customer remits a payment amount that is based on both invoices and credits to their account.

For example, your customer ACME Inc. makes a monthly payment based on their statement. This month, their statement shows invoice #888 for $100 and credit memo #999 issued for $25. ACME Inc. remits a $75 payment. You can create one transaction that applies both the $25 credit memo and the $75 payment to invoice #888.