cannot apply credit memo to a grouped invoice

AI generated answer (using internal Slack threads):

In NetSuite, a Credit Memo can only be applied to open invoices. This is the standard behavior of the system. If an invoice is already paid in full, it will not show up under the Apply List for a Credit Memo. If you want to apply a credit to a fully paid invoice, you would need to delete the payment record first. Then, you can edit the Credit Memo to apply it to the invoice. However, please note that "applying a credit to an invoice" essentially means using it as payment. Therefore, it may not make sense to apply a credit to an invoice that has already been fully paid. If you want to give a refund to a customer, you can create a new Credit Memo from the invoice that was already paid. Applying the Credit Memo will reduce the amount that the customer owes you. You can then click the Refund button on the Credit Memo, which will bring up a Customer Refund document. Alternatively, you can create standalone Credit Memos and use them against future invoices. There's nothing stopping you from posting an unapplied Credit Memo. However, please note that the Credit Memo will be attached to the invoice. ****** Disclaimer: This response was generated by an artificial intelligence assistant based on previous conversations from multiple Slack channels, and may contain inaccuracies or mistakes. ******