How do you move a previously created invoice that is linked to an estimate over to Projects? When I do this, the invoice total changes to $0.

Hi there bistupar-outlook,

It's important that all your transactions be entered correctly for your sales totals to be accurate. QuickBooks Online is a great tool able to help you create and send sales forms, like estimates and invoices, to your customers. I can point you in the right direction for assistance with moving these transactions.

For assistance in moving these transactions so they have the right information in the new project. I recommend reaching out to the QuickBooks Online support team outside of the Community. They'll be able to view the method you're currently using in order to move those transactions in a secure setting in order to help you get those transactions transferred to the new project in the most efficient way possible. =You can reach them using these methods:

Schedule a Callback or start a Chat: click (?)Help in the upper right > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat.
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If you have any other questions, feel free to reach out here.