Why do the invoices have to come from quickbooks? How to delete

Let me help you delete the invoices in QuickBooks Online (QBO). 

When deleting an invoice, you can delete a posted transaction, so this will affect your report totals and the customer's balance. Also, any unbilled charges, credits, billable time, or billable expenses that had been included on the invoice are again available to be included on the next invoice you create. After you process a payment from a customer, you need to record it in QuickBooks to mark the invoice as paid. Otherwise, the invoice stays open and remains unpaid on your reports.

To delete an invoice, follow the steps below:

1. Go to Get paid & pay and select Invoices (Take me there).
2. Find and select the invoice you wish to delete.
3. On the Invoice page, press More at the bottom then Delete.
4. Click Yes to confirm.

You can also delete invoice(s) from the Invoices list. Here's how: 

1. Go to Get paid & pay and select Invoices (Take me there).
2. Find the invoice(s) you wish to delete.
3. Go to the Action column and from the dropdown, press Delete.

Once the invoice has been deleted, you can only view it from the Audit Log. If you're trying to void your invoice rather than delete it, check out this article: Void an invoice.

Furthermore, you may refer to this article as your guide in recording customer payments in QBO: Record invoice payments in QuickBooks Online. Doing so marks the invoice as paid and ensures it doesn't appear as open in your reports.

Please don't hesitate to post in the Community whenever you have additional questions about managing your invoices. We're always available in this forum to assist you further. Stay safe and have a great day ahead.