I accidentally applied an action to all transactions. Can I undo this?

You're unable to undo the action, Fhhondo. However, you can change the transaction's type and category if they're incorrect. 

I'm here to help you. You'll have to change the transaction one by one. Here's how:

1. Click Transactions.
2. Select one transaction.
3. Change the Type and Category.
4. Click Save. 

Let me also include this article as a future reference: Categorize transactions in QuickBooks Self-Employed.

Reach out to us if you need more of our help. The Community is available 24/7 to assist you. Take care!