I accidentally duplicated an invoice number with a client. They already paid it through QB. Can I delete it and create a new one and mark that as PAID?

Jumping in to quickly help with your question about correcting invoices in QuickBooks, gamandes.

When creating an invoice, QuickBooks would automatically use the next transaction number from the last invoice. Although, the invoice number can still be used if manually edited. 

You can delete and recreate the invoice with the correct number to update your record. Then, manually mark it as Paid. It will also not affect the payment that was made online since it was already processed. Here's how to delete and recreate the invoice:

1. Look for the invoice in the Invoices tab.
2. Click the drop-down list beside View, then select Delete.
3. Select Yes.

Once done, recreate the invoice by clicking the Create invoice button and entering the same details. once done, click the Mark as paid button under the Action column. 

I'd also like to share a couple more articles for more references and guidance when working in QBSE:

• QuickBooks Self-Employed Overview 
• Export Transactions and Get Reports in QuickBooks Self-Employed 

As always, you can go back to this thread or visit us again in the Community if you need anything else. We'll make sure that everything is working fine.

Thank you. I have to manually edit my numbers because my invoices have client numbers attached to them. However, I wish QB had a pop up that says "this is a duplicate invoice number, do you want to proceed?" with yes/no buttons. There is a small note underneath while you're creating the invoice, but it's easy to miss.

Thank you. I attach my client number to each invoice number, so I have to change them manually. However, the tiny message that comes up briefly saying "you already used this invoice number" is easy to miss. I wish QB had a pop up that said "this is a duplicate invoice number, do you want to proceed?" with yes/no buttons. 

Good morning, @gamandes. 

Thanks for the additional information. 

I'd be more than happy to send over your feedback to our Product Developers. They'll take the time to review your request and then consider it in the next available update. 

The Community is always here to lend a helping hand. I'm only a post away if you need me. Have a great day!