After a customer accepts your estimate/quote, you can easily turn it into an invoice for billing. (If you want to partially invoice your customer, use progress invoicing instead.)
Here's how to convert an estimate/quote into an invoice:
From the left menu, select Sales, then choose All Sales.
Find and open the estimate/quote.
Select Create invoice.
Add more details to the invoice as necessary, then select Save and close.
Note • You can only invoice an estimate/quote with Accepted or Pending status. To update the status of the estimate/quote, select the drop-down under the customer name. • Estimates/Quotes imported from QuickBooks Desktop show as Closed in QuickBooks Online.
Now you're able to invoice an estimate/quote for your customer.