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Unless you specify otherwise, the system by default will automatically apply the credit note as a payment to the invoice used as the basis. If the credit note amount is greater than the invoice balance, then the excess amount of credit note will be used as an advance for other (not listed) invoices.
Thus, if you want to apply the credit note against the original invoice, you can leave this tab as it is. If you want to use the credit note as an advance payment for other invoices, click Fill by Balances, and then select the Advance check box for each line.
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