I linked an expense to a project and added it to the invoice. Accidentally typed in the product service column and then the linked expense lost. can I undo this action?

Hello cameronmcintosh1,

Mistakes like these are common but don't worry, I'll be happy to help untangle this for you. QuickBooks is designed for business owners like you that enjoy saving time while streamlining their business. 

QuickBooks offers a powerful feature called the Audit log. The Audit Log tracks user login/logout activity, changes to settings, customers, suppliers, and employees. Since you're looking to reverse transactions made in error, using the audit log allows you to locate each transaction entry on the account faster. Check out the steps below for more info:

1. Go to Settings ⚙ and select Audit Log.
2. Select Filter.
3. Use the fields on the Filter panel to choose the appropriate User, Date, or Events filter to narrow the results.
4. If you've recently created these transactions, locate them on the Audit log screen, click on the blue link to open the transaction in question and if you need to delete unwanted entries, you can easily do that from here. 
5. Select Apply.  

There you go, you now know how to use the Audit log to correct/track errors that were made on your account. Give this a try and if you have questions, don't hesitate to reach back, I'm here to steer you in the right direction. 

Otherwise, enjoy the rest of your week!