It happens often that when you meant to click "Cash" you clicked "Credit Card" out of habit. The sale goes through, and then when you reconcile at the end of the day, you realize what happened.
Change it to the proper tender type
- Go to "Sales".
- Find the sale that was wrong.
- Click on the payment type that you wish to change.
- In the dropdown, select the payment type you want to change it to.
- Click "Confirm".
- After the page reloads, make sure it looks right.
Everything's wrong, not just payment
If the whole sale is just one big mistake, then check out how to void a sale here.