Your client will not be able to see the modifications to the invoice in QuickBooks Online (QBO) until you send it to them, Southernfixings.
When you make changes to the invoice, such as adding extra charges for labor and materials, those updates are only visible to you in your QBO account while the invoice is in draft mode or being edited. The client will not see these updates until you have sent the invoice.
I suggest informing the client of any extra charges, particularly if they exceed the original estimate, by using the Note to customer field on the invoice. This will help keep them informed. After you finalize and send the updated invoice, it will be shared with the client.

Additionally, you can visit this article to learn how to customize and include specific information in your sales forms: Customize invoices, estimates, and sales receipts in QuickBooks Online.
Moreover, did you know we provide a complimentary session with our QuickBooks Live Expert Assisted service? Our experts excel at making financial management effortless and offer tailored advice, especially in managing your sales.
We're here to help ensure everything is set up correctly for your business needs. Just count us in if you need more help with handling your sales in QBO.