Hi, I would like to cancel an invoice I sent. The customer won' pay us and I would to create a credit memo. Can you please let me know how to do it? Thank you

Hello @tiphaine, it's wonderful to have you here in the Community!

Once the invoice has been sent to the customer, you can't cancel it. However, you can create a credit memo and apply it to an invoice, marking it as paid. I'd be glad to walk you through the steps.

Here's how:

1. Go to the Gear icon, then choose Account and settings.
2. Open the Advanced tab.
3. In the Automation section, click Edit.
4. Turn on Automatically apply credits to apply credit memos to customer balances or open invoices. Turn it off to manually choose which open invoices to apply credit memos.
5. Hit Save, then Done.
6. Click the +New button.
7. Select Credit memo. 
8. Under the Customer dropdown, pick the customer's name.
9. Fill in the credit memo details, such as the date and the amount.
10. Hit Save and close.

After making a credit memo, you can apply it to an invoice by following the steps outlined in the Step 3 section of this article: Create and apply credit memos or delayed credits in QuickBooks Online. Then, you can send a customer statement to let your customer know that a credit memo has already been applied to their invoice. 

In case you want to generate and send the same invoice to multiple customers, you can check out this article for more guidance: Create the same invoice for multiple customers in QuickBooks Online.

Please let me know if you need further assistance in producing a credit memo. I've got your back.