Need to save invoice single copy how to do ?

Hello there, roopa.

Let me share with you on how you can save a single copy of an invoice within QuickBooks Online.

Once you've saved an invoice, we can follow the steps below to have another one. Here's how:

1. Go to Sales on the left panel.
2. Within the Customers tab, find the name of the customer where the transaction is associated.
3. Then, click their name and locate the invoice you'll want to save a copy. Note: Use the Filter drop-down arrow to select a type of transaction (Invoice) as well as the correct dates. It helps you find the invoice easily.
4. Under the Action column, click the drop-down arrow next to Receive payment link.
5. Select Copy. Then, Save.

Here are the sample screenshots for additional reference:
 

That will do. Also, you may want to learn about customizing an invoice template. You can look into these articles to gather additional information on how to do it in QBO mobile app and web browser:

• Personalise invoice template.
• Customise invoices on the mobile app.

 Please let me know if there's anything else I can help you with. I'll be here to back you up anytime. Take care and have a good one!